Table of contents for issue 1, volume 988, The Astrophysical Journal

A data set of 23,351 globular clusters (GCs) and ultracompact dwarfs (UCDs) in the Coma cluster of galaxies was built using Hubble Space Telescope Advanced Camera for Surveys data. Based on the standard magnitude cut of M_V ≤ −11, a total of 523 UCD candidates are found within this data set of compact stellar systems (CSS). From a color–magnitude diagram analysis built using this catalog, we find a clear mass–magnitude relation extending marginally into the UCD parameter space. The luminosity function defined by this data set shows an excess of sources at bright magnitudes, suggesting a bimodal formation scenario for UCDs. We estimate the number of UCDs with a different origin than GC to be N_UCD ≳ 32 ± 1. We derive the total number of CSS within the core (1 Mpc) of Coma to be N_CSS ≈ 69,400 ± 1400. The radial distribution of UCDs in Coma shows that, like GCs, UCDs agglomerate around three giant ellipticals: NGC 4874, NGC 4889, and IC 4051. We find UCDs are more centrally concentrated around these three ellipticals than GCs. IC 4051 has a satellite population of UCDs similar to NGC 4874 and NGC 4889. We estimate only ∼14% of UCDs inhabit the intracluster space (ICUCD) between galaxies in the region, in comparison to ∼24% for GCs (ICGC). We find red (metal-rich) UCDs are more likely located closer to a host galaxy, with blue (metal-poor) UCDs showing a greater dispersion and lower average density in the region.

Cyanogen (C₂N₂) has been suspected for a long time to be present in comets and to contribute to the creation of the CN radical. So far no observations with ground-based facilities have managed to detect this species, but the Rosetta mission, thanks to in situ observations with the ROSINA mass spectrometer, detected this species in the coma of 67P/Churyumov–Gerasimenko. To investigate its presence from infrared spectra in other comets, we developed a fluorescence model for the ν₃ fundamental band. From new laboratory high-resolution infrared spectra of cyanogen, we analyzed the region of the ν₃ band of C₂N₂, centered around 4.63 μm (2158 cm⁻¹). In addition to line positions and intensities, molecular parameters for the ground and excited vibrational state were obtained. These parameters allowed us to develop a fluorescence model for cyanogen. Line-by-line excitation rates of the ν₃ band of cyanogen in cometary comae are presented. An upper limit of the abundance of cyanogen in a spectrum of comet C/2022 E3 (ZTF) is discussed.

Models of active galactic nuclei (AGN) often invoke a close physical association between the broad-line region (BLR) and the accretion disk. We evaluate this theoretical expectation by investigating the relationship between the inclination angle of the BLR (θ_BLR) and the inclination angle of the inner accretion disk (θ_disk). For a sample of eight AGN that have published values of θ_BLR estimated from dynamical modeling of the BLR based on velocity-resolved reverberation mapping experiments, we analyze high-quality, joint XMM-Newton and NuSTAR X-ray observations to derive new, robust measurements of θ_disk through broadband (0.3–78 keV) reflection spectroscopy. Mock spectra demonstrate that the results are generally not strongly affected by warm absorbers or the model used to fit the soft-band data. We find a strong, positive correlation between θ_BLR and θ_disk (Pearson correlation coefficient 0.856, p-value 0.007), although Monte Carlo simulations indicate that the level of significance is only marginal (<3σ). Nevertheless, the nearly linear relation between θ_BLR and θ_disk suggests a possible physical alignment between the accretion disk and the BLR. Future studies with a larger and more homogeneous sample are needed to confirm the correlation and refine our understanding of the structure and dynamics of the central regions of active galaxies.

We performed spectroscopic analyses of five local compact star-forming galaxies (CSFGs) with extremely high [O iii]/[O ii] (O₃₂) ratios (>20). These targets remarkably share similar properties with high-redshift C iv emitters at z > 6: high Hβ equivalent widths (EWs > 200Å), extreme O₃₂ ratios, low metallicities (12+log(O/H) ≲ 7.8), low C/O abundances (log(C/O) < −0.7), and high ionization conditions (logU > −2). The ultraviolet (UV) spectra were acquired using the Hubble Space Telescope’s (HST) Cosmic Origins Spectrograph and Space Telescope Imaging Spectrograph. We have identified a wealth of rest-frame UV emission lines (C iv, He ii, O iii], C iii]) in the HST spectra. Notably, all our targets show intense C iv emission lines with rest-frame EWs > 10 Å, indicative of hard ionizing radiation. The rest-frame UV emission line diagnostics disfavor an active galactic nucelus and could be consistent with significant shock contributions to the source of ionizing radiation. Four of our targets show high C iv/C iii] ratios (≥1.4), suggestive of strong Lyman-continuum leakage (LyC escape fraction, f_esc,LyC > 10%) from these sources. This is consistent with their Lyα-inferred LyC escape fractions (f_esc,LyC = 9%–31%). We derive relative C/O abundances from our sources, showing log(C/O) values from −1.28 to −0.77, comparable to those of reionization-era galaxies at z ≳ 6. The properties of the CSFGs, particularly their intense C iv emission and high O₃₂ ratios, which suggest significant LyC escape fractions, are similar to those of the reionization-era C iv emitters. These similarities reinforce the hypothesis that these CSFGs are the closest analogs of significant contributors to the reionization of the intergalactic medium.

The dust extinction curve is typically parameterized by a single variable, R(V), in optical and near-infrared wavelengths. R(V) controls the slope of the extinction-versus-wavelength curve, and is thought to reflect the grain-size distribution and composition of dust. Low-resolution, flux-calibrated BP/RP spectra from Gaia have allowed the determination of the extinction curve along sightlines to 130 million stars in the Milky Way and Magellanic Clouds. We show that these extinction curves contain more than a single degree of freedom—that is, that they are not simply described by R(V). We identify a number of components that are orthogonal to R(V) variation, and we show that these components vary across the sky in coherent patterns that resemble interstellar medium (ISM) structure. These components encode variation in the 770 nm extinction feature, intermediate-scale and very broad structure, and a newly identified feature at 850 nm, and they likely trace both dust composition and local conditions in the ISM. Correlations of the 770 and 850 nm features with R(V) suggest that their carriers become more abundant as the carrier of the 2175 Å feature is destroyed. Our 24 million extinction-curve decompositions and feature equivalent-width measurements are publicly available at doi:10.5281/zenodo.14005028.

We examine the impact of the magnetic field on Population III star formation by varying its strength. We perform simulations with magnetic field strengths ranging from 10⁻²⁰ G to 10⁻⁴ G, in addition to a model without a magnetic field. The simulations are run for >1000–1400 yr after the first protostar forms. In weak-field models, the surrounding disk fragments, forming multiple protostars, and the magnetic field is amplified by the orbital motion and rotation of these protostars. In the model without a magnetic field, frequent fragmentation occurs, and the most massive protostar reaches ∼200 M_⊙. However, in models with a magnetic field, once the magnetic field is amplified, the protostars merge to form a single massive protostar, and no further fragmentation occurs except in the model with the strongest magnetic field. Even after the formation of the single protostar, the magnetic field continues to amplify, leading to the formation of a thick disk supported by magnetic pressure and a global spiral pattern. In models with moderate or strong magnetic fields, a rotating disk can form, but fragmentation does not occur, and a strong magnetic field drives an outflow. However, the range of parameters for both disk formation and outflow driving is very narrow, making their appearance under realistic conditions unlikely. Given the weak magnetic field in the early Universe, Population III stars are expected to form as single stars, surrounded by a thick disk with a spiral pattern. Thus, the magnetic field, regardless of its strength, plays a crucial role in Population III star formation.

It has been suggested that Jupiter’s fuzzy core could be a result of a giant impact. Here, we investigate the expected impact conditions from N-body simulations. We then use state-of-the-art smoothed particle hydrodynamics simulations to investigate the results of impacts with different conditions including various impactor masses and composition, different formation stages in Jupiter’s growth, and different resolutions. We next simulate the long-term thermal evolution of Jupiter postimpact. We find that 3D N-body simulations predict rather oblique impacts, and that head-on collisions are rare. Moreover, our results show that, even under a head-on collision, Jupiter’s fuzzy core cannot be formed. We next simulated Jupiter’s thermal evolution and showed that, unless postimpact temperatures are extremely low, a giant impact would not lead to an extended dilute core as inferred by interior models. We conclude that Jupiter’s fuzzy core is not caused by an impact and is likely to be an outcome of its formation process.

Metallicities of both gas and stars decline toward large radii in spiral galaxies, a trend known as the radial metallicity gradient. We quantify the evolution of the metallicity gradient in the Milky Way as traced by APOGEE red giants with age estimates from machine learning algorithms. Stars up to ages of ∼9 Gyr follow a similar relation between metallicity and Galactocentric radius. This constancy challenges current models of Galactic chemical evolution, which typically predict lower metallicities for older stellar populations. Our results favor an equilibrium scenario, in which the gas-phase gradient reaches a nearly constant normalization early in the disk lifetime. Using a fiducial choice of parameters, we demonstrate that one possible origin of this behavior is an outflow that more readily ejects gas from the interstellar medium (ISM) with increasing Galactocentric radius. A direct effect of the outflow is that baryons do not remain in the ISM for long, which causes the ratio of star formation to accretion, , to quickly become constant. This ratio is closely related to the local equilibrium metallicity, since its numerator and denominator set the rates of metal production by stars and hydrogen gained through accretion, respectively. Building in a merger event results in a perturbation that evolves back toward the equilibrium state on ∼Gyr timescales. Under the equilibrium scenario, the radial metallicity gradient is not a consequence of the inside-out growth of the disk but instead reflects a trend of declining with increasing Galactocentric radius.

The morphology of circular polarization profiles from solar spectropolarimetric observations encodes information about the magnetic field strength, inclination, and line-of-sight velocity gradients. Previous studies used manual methods or unsupervised machine learning (ML) to classify the shapes of circular polarization profiles. We trained a multilayer perceptron comparing classifications with unsupervised ML. The method was tested on quiet Sun data sets from Daniel K. Inouye Solar Telescope (DKIST), Hinode, and GREGOR, as well as simulations of granulation and a sunspot. We achieve validation metrics typically close to or above 90%. We also present the first statistical analysis of quiet Sun DKIST/ViSP data using inversions and our supervised classifier. We demonstrate that classifications with unsupervised ML alone can introduce systemic errors that could compromise statistical comparisons. DKIST and Hinode classifications in the quiet Sun are similar, despite our modeling indicating spatial resolution differences should alter the shapes of circular polarization signals. Asymmetrical (symmetrical) profiles are less (more) common in GREGOR than DKIST or Hinode data, consistent with narrower response functions in the 1564.85 nm line. Single-lobed profiles are extremely rare in GREGOR data. In the sunspot simulation, the 630.25 nm line produces “double” profiles in the penumbra, likely a manifestation of magneto-optical effects in horizontal fields; these are rarer in the 1564.85 nm line. We find the 1564.85 nm line detects more reverse polarity magnetic fields in the penumbra, in contradiction to observations. We detect mixed-polarity profiles in nearly one fifth of the penumbra. Supervised ML robustly classifies solar spectropolarimetric data, enabling detailed statistical analyses of magnetic fields.

Pair-instability supernovae (PISNe) are predicted thermonuclear explosions of massive stars with helium core masses exceeding ∼65M_⊙, and they synthesize substantial amounts of radioactive ⁵⁶Ni (M(⁵⁶Ni) ∼ 60 M_⊙ in extreme cases). To investigate their observational signatures, we developed a multi-D Monte Carlo radiation transport code, assuming spherical symmetry in the background medium and the photon sources distribution, and performed simulations of gamma-ray and hard X-ray emissions from the decay chain ⁵⁶Ni→⁵⁶Co→⁵⁶Fe. We find that key gamma-ray lines (847 and 1238 keV) from ⁵⁶Co decay in the 130 M_⊙ helium core model can be detected up to 300–400 Mpc by next-generation MeV gamma-ray telescopes. In contrast, the signals from the 100 M_⊙ model remain below the detection limits. Our results provide the template for gamma-ray follow-up observations of PISNe. Considering theoretical predictions and observational constraints, we estimate PISN event rates within 300 Mpc to be approximately 0.01–0.1 events per year, highlighting their rarity but also emphasizing their feasibility as targets for future gamma-ray observations over the decade.

In this study, we present a detailed analysis of single-pulse emission from the rotating radio transient (RRAT) J2325−0530, observed at 1250 MHz using the Five-hundred-meter Aperture Spherical Radio Telescope. A total of 168 burst pulses were detected within 0.8 hr of observation, yielding a detection rate 3 to 4 times higher than those previously reported. For the first time in this RRAT, we detected sequences of consecutive single-pulse emission lasting two to six spin periods. The single pulses exhibit significant variability in linear polarization, circular polarization, and polarization position angle, while the average profile displays weak polarization and a complex position angle structure. The distributions of fluence and waiting time, together with the significant correlation between fluence and pulse width, indicate that the emission behavior of RRAT J2325−0530 resembles that of giant pulse phenomena. We also measured the scintillation bandwidth and timescale at 1250 MHz to be 3.45 ± 0.07 MHz and 16.67 ± 0.35 minutes, respectively. In three single pulses, we detected quasiperiodic microstructure in the Stokes I, L, and V parameters, with differing microstructure periods across these components. Nevertheless, the observed microstructure periods follow the known linear relationship with the pulsar rotation period. These results support the view that RRATs share the same underlying emission physics of normal pulsars, while also revealing additional complexity in the origin of microstructure.

Diffuse Galactic light (DGL) is starlight scattered by interstellar dust. In visible wavelengths, earlier studies observed DGL toward regions of low optical depth in high Galactic latitude, and show marginal consistency with a theoretical model assuming single scattering by dust grains. However, a model for DGL in regions of high optical depth has not been established. In this study, we analyze wide-field imaging data toward a region of high optical depth near the Galactic center, which was obtained with the Optical Navigation Camera on board the Hayabusa2 spacecraft. The data are reduced by dark-current and stray-light subtraction, flat-field correction, and sensitivity calibration for the DGL measurement. In the image, we select dark low-intensity areas where background starlight is highly absorbed by interstellar dust, and extract the DGL component by masking pixels contaminated by stars. As a result, we find that the DGL intensity decreases toward high optical depth, and this trend is reversed from the previous measurements in optically thin regions. To explain the observed trend, we introduce DGL models inferred from a radiative transfer equation in a plane-parallel dusty slab. By assuming literature values for the albedo and scattering asymmetry factor of interstellar dust, the measured DGL intensity can be fitted by a model in which a dust slab without internal emitters is illuminated by backside stars.

PKS 1510−089 is one of the most peculiar sources among the flat spectrum radio quasars, exhibiting a notable big blue bump. This provides a unique opportunity to explore the coupling between the activity of the central engine and the relativistic jet, offering further insight into the origin of the multiwavelength emissions. To this end, we collected multiwavelength data spanning four periods from 2008 to 2015 and performed the spectral energy distribution (SED) modeling using a one-zone homogeneous leptonic model. In the model, a multichromatic accretion disk (AD) is used to fit the optical/UV data sets, while the external radiation fields from the broad-line region (BLR) and dusty torus (DT) are properly considered to produce the high-energy γ-ray emissions. Our best fit to 12 SEDs yields the following results: (i) The innermost stable orbit (R_ISO) of the AD is not stable but varies between 3 R_S and 18 R_S during these observations. (ii) The high-energy hump of the SED is well dominated by Compton scattering of the BLR photons, while the X-ray flux may be comprised of multiple radiation components. (iii) The γ-ray emitting regions are generally matter-dominated, with low magnetization, and are located beyond the BLR but within the DT. At such distance, the multiwavelength emissions are likely to originate from shock accelerations. (iv) For the energization of the relativistic jet, our study supports the Blandford−Znajek mechanism, instead of the Blandford−Payne mechanism, as the latter fails to power the jet.

We investigate the complex magnetic reconnection process between the filament and surrounding loops during the failed filament eruption that occurred in NOAA active region 13445 on 2023 September 24, using extreme-ultraviolet observations from the Solar Dynamics Observatory and high-resolution Hα imaging from the New Vacuum Solar Telescope. This failed filament eruption is associated with an M4.4 flare (SOL2023-09-24T03:28). At the early phase of the filament eruption, the filament displays a distinct clockwise rotational motion, suggesting an untwisting motion. During the flare precursor phase, the northwest slipping motion of the brightenings at the filament’s left footpoint, along with the brightening and continuous expansion of the nearby loops at the northwest, suggest the occurrence of a slipping magnetic reconnection between the filament and peripheral loops at the quasi-separatrix layer. After the slipping motion begins, significant brightenings of filament materials and multiple bright structures moving toward the two filament footpoints are observed during the two episodes of magnetic reconnection between the filament and the overlying loops, with the most prominent brightenings and the moving structures occurring during the main phase of the M4.4 flare. The observed untwisting motion of the filament and the twist reduction derived from the nonlinear force-free field extrapolation suggest that the magnetic reconnection between the filament and the peripheral and overlying loops plays a significant role in the failure of the filament eruption by greatly reducing its twist.

We investigate the evolution of star clusters containing intermediate-mass black holes (IMBHs) of 300–5000 M_⊙, focusing on the formation and evolution of IMBH–stellar-mass black hole (M_BH ≲ 10²M_⊙) binaries. Dense stellar systems like globular clusters (GCs) or nuclear star clusters offer unique laboratories for studying the existence and impacts of IMBHs. IMBHs residing in GCs have been under speculation for decades, with their broad astrophysical implications for the cluster’s dynamical evolution, stellar population, and gravitational-wave (GW) signatures, among others. While existing GW observatories, such as the Advanced Laser Interferometer Gravitational-wave Observatory (aLIGO), target binaries with relatively modest mass ratios, q ≲ 10, future observatories, such as the Einstein Telescope (ET) and the Laser Interferometer Space Antenna (LISA), will detect intermediate-mass ratio inspirals (IMRIs) with q > 10. This work explores the potential for detecting IMRIs by adopting these upcoming telescopes. For our experiments, we perform multiple direct N-body simulations with IMBHs, utilizing Nbody6++GPU, after implementing the GW merger schemes for IMBHs. We then study the statistical properties of the resulting IMRIs, such as the event rates and orbital properties. Assuming that IMRIs with a signal-to-noise ratio ​​> 8 are detectable, we derive the following detection rates for each observatory: ≲0.02 yr⁻¹ for aLIGO, ∼101−355 yr⁻¹ for ET, ∼186−200 yr⁻¹ for LISA, ∼0.24−0.34 yr⁻¹ for aSOGRO, and ∼3880−4890 yr⁻¹ for DECIGO. Our result confirms the capability of detecting IMRIs with future GW telescopes.

The soft X-ray excess and Fe Kα emission lines are widely observed in Seyfert galaxies, with their origin still in debate. We present a detailed spatially resolved image and spectral analysis of the Seyfert 2 galaxy NGC 1068 using high-resolution Chandra ACIS data. We find that the soft X-ray emission and iron emission show extended structures in the northeast and southwest directions. Especially, the soft X-ray extends predominantly in the 1^″−15^″ (∼72 pc–1 kpc) northeast sector with a distance of at least ∼10^″ (∼700 pc), and its 0.5–3.0 keV flux is about ∼2/3 of that from the 1^″ radius circular region centered on the core of NGC 1068. We fit the soft X-ray spectra from the core and two bright blobs (∼3^″, S1 and ∼15, S2 from the nucleus) as a dual-temperature plasma with two APEC models. Our analysis suggests that the extended soft X-ray emission in NGC 1068, as well as contributions to Fe Kα emission from the extended region, likely originate from the interactions between the jet and the interstellar medium, offering further insights into the origin of soft X-ray excess and Fe Kα emission lines in similar Seyfert sources. However, extended X-ray emission outside the ionization cone might be influenced by additional processes; future multiwavelength observations will be needed to test these possibilities.

We explore the accretion rates of supermassive black holes (SMBHs) in late-stage galaxy mergers by observing three ultraluminous infrared galaxies (ULIRGs), IRAS 14378-3651, IRAS 17208-0014 and IRAS 23365+3604, using the JWST/MIRI Medium Resolution Spectrometer and JWST/NIRSpec integral field unit. In all three cases, we fail to detect [Ne vi] λ7.65 μm, a robust active galactic nuclei (AGN) tracer lying in a low-opacity interstellar window, nor do we detect any other lines that might indicate AGNs. The only detected high-excitation emission line, [Mg iv] (λ4.488 μm), arises from shocks associated with supernovae. Our new, deep flux limits on AGN tracers in the near- and mid-infrared indicate that the nuclear obscuration of any purported AGNs in our sample is isotropic, i.e., the far-infrared luminosities of these galaxies are unlikely to be driven by escaping AGN power. This allows us to show that the Eddington ratios of their SMBHs are low. We then assemble an unbiased sample of 19 ULIRGs (from the IRAS Bright Galaxy Sample with L(TIR) ≥ 10¹²L_⊙) in late-stage mergers and show that their dynamically measured black hole masses are consistent with the values from scaling from their stellar masses. On this basis, we show that the Eddington ratios of any AGNs in 15 of these galaxies are also very low, ≲10%. This indicates that any black holes are in a relatively quiescent state. That is, high levels of accretion are found in only a minority of late-merger-phase ULIRGs.

Magnetic flux tubes in the presence of background rotational flows are abundant throughout the solar atmosphere and may act as conduits for MHD waves to transport energy throughout the solar atmosphere. Here we investigate the contribution from MHD waves to the Poynting flux in a 3D numerical simulation of a realistic solar atmosphere, modeling a structure resembling a solar vortex tube, using the PLUTO code in the presence of different plasma flow configurations. These simulations feature a closed magnetic loop system where a rotational flow is imposed at one footpoint in addition to photospheric perturbations acting as a wave driver mimicking those of p-modes. We find that a variety of MHD waves exist within the vortex tube, including sausage, kink, and torsional Alfvén waves, owing to the photospheric wave driver and the nature of the rotational flow itself. We demonstrate how the visual interpretation of different MHD modes becomes nontrivial when a background rotational flow is present compared to a static flux tube. By conducting a simulation both with and without the rotational plasma flow, we demonstrate how the perturbed Poynting flux increases in the presence of the rotational flow as the waves transport increased magnetic energy. We attribute this increase to the dynamical pressure from the rotational flow increasing the plasma density at the tube boundary, which acts to trap the wave energy more effectively inside the vortex. Moreover, we demonstrate how the Poynting flux is always directed upward in weakly twisted magnetic flux tubes.

We report the first successful Atacama Large Millimeter/submillimeter Array (ALMA) follow-up observations of a secure z > 10 JWST-selected galaxy, by robustly detecting (6.6σ) the [O iii]_{88 μm} line in JADES-GS-z14-0 (hereafter GS-z14). The ALMA detection yields a spectroscopic redshift of z = 14.1793 ± 0.0007, and increases the precision on the prior redshift measurement of from NIRSpec by ≳180×. Moreover, the redshift is consistent with that previously determined from a tentative detection (3.6σ) of C iii]_1907,1909 (z = 14.178 ± 0.013), solidifying the redshift determination via multiple line detections. We measure a line luminosity of L_{[O iii]88} = (2.1 ± 0.5) × 10⁸L_⊙, placing GS-z14 at the lower end, but within the scatter of, the local L_{[O iii]88}–star formation rate relation. No dust continuum from GS-z14 is detected, suggesting an upper limit on the dust-to-stellar mass ratio of <2 × 10⁻³, consistent with dust production from supernovae with a yield y_d < 0.3 M_⊙. Combining a previous JWST/MIRI photometric measurement of the [O iii]λλ4959,5007 Å and Hβ lines with Cloudy models, we find GS-z14 to be surprisingly metal-enriched (Z ∼ 0.05–0.2 Z_⊙) a mere 300 Myr after the Big Bang. The detection of a bright oxygen line in GS-z14 thus reinforces the notion that galaxies in the early Universe undergo rapid evolution.

Recently, Y. Zhang & S. Liu proposed a turbulent convection model for multiscale anisotropies of cosmic rays (CRs), with an assumption of isotropic diffusion such that the anisotropies are statistically isotropic. However, this assumption may be unrealistic for TeV CRs, whose observations have revealed the significance of the local interstellar background magnetic field. To meet the difficulty, the turbulent convection scenario needs to be extended to cover anisotropic diffusion. In this paper, we focus on the parallel diffusion with isotropic pitch-angle scattering, which may be an approximation to the transport process driven by weak hydromagnetic waves in a magnetic flux tube, where fluctuations of the wave velocities lead to the turbulent convection. The consequence is the breaking of the statistical isotropy, while the overall shape of the angular power spectrum, (ℓ ≫ 1), remains similar to that in the isotropic diffusion model, where ℓ is degrees of spherical harmonics and γ is the turbulence spectral index of the convection field. It is then expected that the power-law index of the TeV CR small-scale angular power spectrum can be explained with the Kolmogorov law γ = 5/3, irrespective of the background magnetic field to some extent.

Motivated by the discovery of a pulsar in the direction of the old open cluster NGC 6791, we conducted a search for radio pulsars in archival Parkes observations targeting similar old open clusters. We reprocessed 224 observations totalling 75.02 hr from four clusters: Theia 1661, NGC 6259, Pismis 3, and Trumpler 20. Our analysis identified five known pulsars and three new rotating radio transient (RRAT) candidates. By comparing the measured dispersion measures (DMs) with the expected DM values for each cluster derived from YMW16 and NE2001 models, we conclude that most detected sources are likely background pulsars. However, RRAT J1749−25 in Theia 1661 and RRAT J1237−60 in Trumpler 20 have DMs reasonably close to their respective clusters, suggesting possible membership. The association between PSR J1750−2536 and Theia 1661 remains ambiguous due to its intermediate DM. These candidate cluster-associated neutron stars warrant follow-up with more sensitive telescopes such as MeerKAT or the Square Kilometre Array, potentially offering valuable insights into neutron star retention mechanisms and evolution in open cluster environments.

The abundance ratios of radioactive elements U/Th and stable elements Pb/Os from the r-process are found to have a strong correlation. This correlation is quite robust with respect to astrophysical conditions. The U/Th–Pb/Os correlation is applied to provide customized initial abundance ratios U/Th from the observed abundance ratios Pb/Os for six r-process enhanced metal-poor stars. The ages of these six metal-poor stars are predicted by the U/Th chronometer, which are approximately between 11 and 15 Gyr. Their ages are compatible with the cosmic age of 13.8 billion years predicted from the cosmic microwave background radiation.

The Neil Gehrels Swift Observatory (Swift) Burst Alert Telescope (BAT) is a coded aperture gamma-ray instrument with a large field of view that was designed to detect and localize transient events. When a transient is detected, either on board or externally, the BAT saves time-tagged event (TTE) data, which provide the highest-quality information of the locations of the photons on the detector plane and their energies. These data can be used to produce spectra, lightcurves, and sky images of a transient event. While these data products are produced by the Swift Data Center and can be produced by current software, they are often preset to certain time and energy intervals, which have limited their use in the current time domain and multimessenger environment. Here, we introduce a new capability for the BatAnalysis Python package to download and process TTE data under an open-source Python framework that allows for easy interfacing with other Python packages. The new capabilities of the BatAnalysis software allow for TTE data to be used by the community in a variety of advanced customized analyses of astrophysical sources which BAT may have TTE data for, such as fast radio bursts (FRBs), gamma-ray bursts (GRBs), low-mass X-ray binaries (LMXB), soft gamma repeaters, magnetars, and many other sources. We highlight the usefulness of the BatAnalysis package in analyzing TTE data produced by an onboard GRB trigger, an FRB external trigger, a subthreshold detection of the LMXB EXO 0748–676, and an external trigger of a GRB that BAT detected during a slew.

We present a new 8.5 ks Chandra observation of A1885 (z = 0.089), obtained as part of the Cluster Evolution Reference Ensemble At Low-z (CEREAL) survey of ∼200 low-z galaxy groups and clusters. These data reveal that A1885 is a strong cool core, with a central cooling time of Gyr, and that the central galaxy hosts an X-ray-luminous point source at its center (L erg s⁻¹), indicative of a rapidly accreting supermassive black hole (SMBH). In the context of the larger CEREAL sample, we constrain the fraction of clusters at z ∼ 0.15 with X-ray-bright (L₂₋₁₀ > 10⁴² erg s⁻¹) central active galactic nuclei (AGN) to be no more than 4.1% at 95% confidence. Including radio data from LOFAR, the Giant Metrewave Radio Telescope, ASKAP, and the Very Large Array, spanning 44 MHz–150 GHz, and optical integral field unit data from the Sloan Digital Sky Survey's MaNGA, we probe the details of cooling, feeding, and feedback in this system. These data reveal that cooling of the intracluster medium is highly suppressed on large (>10 kpc) scales despite a central SMBH that is in the early stages of the self-regulation cycle (characterized by rapid accretion, physically small jets, and no large-scale low-frequency radio emission). To reconcile the large-scale quenching with a lack of visible large-scale feedback, we propose that the timescale on which energy is dissipated on large scales (>10 kpc) is significantly longer than the timescale on which black hole feeding operates on small (∼parsec) scales. This interpretation disfavors a model in which the energy is rapidly dissipated (e.g., shocks), which would synchronize the feeding and feedback timescales, and favors a model in which the heating effects of AGN feedback can linger long after the outburst has passed (e.g., turbulent mixing).

Significant variability in broad emission line strengths of active galactic nuclei (AGN) over months to years has been observed, often accompanied by intrinsic continuum changes. Such spectral variability challenges the traditional AGN classification scheme, which attributes differences between type 1 and type 2 to geometrical effects, as transitions between these types occur on timescales shorter than viscous ones. In this work, using the cloudy photoionization simulations, we investigated the response of the major emission line fluxes, in the optical/UV and hard X-ray bands, to changes in the intensity and shape of the continuum emission of the AGN under two scenarios: (i) changes in the X-ray power law while keeping disk emission fixed, and (ii) broadband continuum variations. We demonstrate that broad-line region (BLR) line fluxes are insensitive to X-ray power-law changes alone. Considering a well-studied case of the changing-look (CL) AGN Mrk 1018, which exhibits variations in the intrinsic disk emission, as well as the X-ray power law, our simulations reproduce observed brightening and dimming trends of the BLR emission. Moreover, we show that the highly ionized Fe Kα X-ray flux, primarily produced by the H-like and He-like ions of Fe, strongly depends on the X-ray strength of the intrinsic spectral energy distribution. These findings suggest that the origin of highly ionized Fe Kα emission is in the coronal part of the accretion disk and that the CL phenomenon can be triggered by intrinsic changes in the accretion properties of AGN.

We present JWST observations of a gravitationally lensed, extremely metal-poor galaxy at redshift z = 8.203 ± 0.001 from the CANUCS survey. Based on the low oxygen to Balmer line ratios, we infer a gas-phase metallicity of 12 + log(O/H) = 6.85 (1.4% solar), making CANUCS-A370-z8-LAE one of the most metal-poor galaxies known at z > 7. The galaxy has a high Hβ equivalent width of 225 ± 50 Å, small half-light radius of only pc, and high star formation rate density of 50–100 M_⊙ yr⁻¹ kpc⁻². The galaxy shows high-equivalent-width Lyα emission with an inferred Lyα escape fraction of 0.21 ± 0.05. The high escape fraction of Lyα is likely due to the compact starbursting nature of the galaxy combined with its location in an overdensity traced by at least two other galaxies spectroscopically confirmed to lie within δz = 0.01 that have helped to reionize the environment. The low metallicity of CANUCS-A370-z8-LAE is best explained by a model where infalling metal-poor gas dilutes the interstellar medium, rather than being a young galaxy forming its first stellar populations.

Quasars, powered by accretion onto supermassive black holes (SMBHs), exhibit significant variability, offering insights into the physics of accretion and the properties of the central engines. In this study, we analyze photometric variability and its correlation with key quasar properties, including black hole mass (M_BH) and nuclear luminosities, using 915 quasars with 0 ≤ z < 3.0 from the All Quasar Multi-Epoch Spectroscopy sample monitored within the fifth-generation Sloan Digital Sky Survey (SDSS-V). Variability metrics were derived from approximately 6 yr light curves provided by the Zwicky Transient Facility (ZTF), while SMBH masses and luminosities were obtained from the SDSS DR16 quasar catalog of Q. Wu & Y. Shen. We identify a strong anticorrelation between variability amplitude and luminosity, which strengthens with redshift, and a redshift-dependent trend for M_BH: a positive correlation at low redshifts, no significant correlation at intermediate redshifts, and an anticorrelation at the highest redshifts. Our main finding is a robust anticorrelation between photometric variability amplitude and Eddington ratio, consistent across different redshift bins. We present a general equation encapsulating this relationship, which appears to be almost free of redshift dependence, enabling predictions of quasar variability based on accretion parameters or vice versa. The derived relation with the Eddington ratio provides a unified framework for interpreting variability in active galactic nuclei and facilitates future studies of quasar variability using high-cadence surveys, such as the Vera C. Rubin Observatory’s Legacy Survey of Space and Time.

This study investigates the projected, quasi-symmetric ∼46 kiloparsec-scale diffuse radio lobes surrounding the giant elliptical galaxy M87, utilizing well-sampled wideband (60 MHz–10.55 GHz) observations from the Murchison Widefield Array and Very Large Array, supplemented by data from the Low-frequency Array and Effelsberg. The observed structures feature sharp edges and filaments, with nearly uniform and moderately steep spectral indices (α, mostly within −1.2 ≤ α ≤ −0.8), indicating turbulence. Well-sampled radio spectra for the lobes’ diffuse region are derived using the continuous injection (CI) model (with α_inj ≃ −0.86 and ν_b ≃ 1.72 GHz), and for its three localized regions using the impulsive injection model (e.g., the Jaffe–Perola (JP) model). From energy equipartition analysis, we estimate the typical magnetic field strength in the lobes’ diffuse region to be B_eq ≃ 10 μG. The age of the lobes is estimated as ∼30–50 Myr, based on lifetimes derived from the CI and JP models and sound crossing time. Outflow powers of ∼(0.2–2) × 10⁴⁴ erg s^–1 for the lobes’ diffuse components and ∼(1–11) × 10⁴⁴ erg s^–1 for the whole source are calculated. With this power assessment, we conclude that the galactic stellar wind has a negligible effect, and the active galactic nucleus (AGN)-driven jet can provide the necessary energy for the whole system. Furthermore, we argue that while the wind driven by current AGN activity is unlikely to power the lobes’ diffuse components, an average enhancement of AGN activity by a factor of ∼10² over the past ∼30–50 Myr remains plausible.

Tidal disruption events (TDEs) are a class of transients that occur when a star is destroyed by the tides of a massive black hole (MBH). Their rates encode valuable MBH demographic information, but this can only be extracted if accurate TDE rate predictions are available for comparisons with observed rates. In this work, we present a new, observer-friendly Python package called REPTiDE, which implements a standard loss-cone model for computing TDE rates given a stellar density distribution and an MBH mass. We apply this software to a representative sample of 91 nearby galaxies over a wide range of stellar masses with high-resolution nuclear density measurements from C. H. Hannah et al. We measure per-galaxy TDE rates ranging between 10^−7.7 and 10^−2.9 yr^–1 and find that the sample-averaged rates agree well with observations. We find a turnover in the TDE rate as a function of both galaxy stellar mass and black hole mass, with the peak rates being observed in galaxies at a galaxy mass of 10^9.5M_⊙ and a black hole mass of 10^6.5M_⊙. Despite the lower TDE rates inferred for intermediate-mass black holes, we find that they have gained a higher fraction of their mass through TDEs when compared to higher-mass black holes. This growth of lower-mass black holes through TDEs can enable us to place interesting constraints on their spins; we find maximum spins of a_• ≈ 0.9 for black holes with masses below ∼10^5.5M_⊙.

Recent observations indicate that stripped-envelope core-collapse supernovae are often surrounded by dense circumstellar material (CSM). Motivated by this, we develop an analytic model to systematically study the dynamics of long gamma-ray burst (LGRB) jet propagation in various CSM environments. We derive a general expression for the jet head velocity (β_h) and breakout time (t_b) valid across Newtonian, relativistic, and intermediate regimes, accounting for a previously unrecognized dependence on 1 − β_h. Our results highlight a fundamental distinction between jet propagation in massive stars, where β_h ≪ 1, and in extended CSM, where 1 − β_h ≪ 1. We establish an analytic success/failure criterion for jets and express it in terms of jet and CSM parameters, revealing a strong dependence on CSM radius. To quantify the relativistic nature of the jet-cocoon system, we introduce the energy-weighted proper velocity . We identify three possible jet outcomes—(a) successful jets (), (b) barely failed jets (), and (c) completely failed jets ()—and constrain their respective jet/CSM parameter spaces. We show that, in (b) and (c), large CSM radii can result in luminous fast blue optical transients via cocoon cooling emission. This theoretical framework provides a basis for future observational and theoretical studies to understand the link between LGRBs, intermediate GRBs, low-luminosity LGRBs, and their environments.

The atmospheres of low-temperature stars, brown dwarfs, and exoplanets are challenging to model due to strong molecular features and complex gas and condensate chemistry. Self-consistent atmosphere models are commonly used for spectral fitting, but computational limits restrict the production of finely sampled multidimensional parameter grids, necessitating interpolation methods to infer precise parameters and uncertainties. Here, we compare two grid model fitting approaches: a Markov Chain Monte Carlo (MCMC) algorithm interpolating across spectral fluxes, and a random forest retrieval (RFR) algorithm trained on a grid model set. We test these with three low-temperature model grids—Sonora Diamondback, Sonora Elf Owl, and Spectral ANalog of Dwarfs (SAND)—and a sample of 11 L and T dwarf companions to FGKM stars with known distances, compositions, and ages. Diamondback models are optimal for early- and mid-type L dwarfs, Elf Owl for mid and late T dwarfs, and SAND for young L dwarfs and L/T transition objects. The MCMC approach yields higher fit quality and more precise parameters, though best-fit parameters are generally consistent between approaches. RFR analysis is orders of magnitude faster after training. Both approaches yield mixed results when comparing fit parameters to expected values based on the primary (metallicity and surface gravity) or evolutionary models (temperature and radius). We propose modeling low-temperature spectra efficiently by first fitting multiple model sets using RFR, followed by a more accurate MCMC assessment, to accelerate improved grid development.

We present extensive follow-up time-series photometry of WD J0049−2525, the most massive pulsating white dwarf currently known, with T_eff = 13,020 K and cm s⁻². The discovery observations detected only two significant pulsation modes. Here, we report the detection of 13 significant pulsation modes ranging from 170 to 258 s based on 11 nights of observations with the New Technology Telescope, Gemini, and Apache Point Observatory telescopes. We use these 13 modes to perform asteroseismology and find that the best-fitting models (under the assumption of an ONe core composition) have M_⋆ ≈ 1.29M_⊙, a surface hydrogen layer mass of , and a crystallized core fraction of >99%. An analysis of the period spacing also strongly suggests a very high mass. The asteroseismic distance derived is in good agreement with the distance provided by Gaia. We also find tentative evidence of a rotation period of 0.3 or 0.67 days. This analysis provides the first look at the interior of a ∼1.3 M_⊙ white dwarf.

A major challenge in solar physics is to obtain empirical information on the magnetic field of the million-degree plasma of the solar corona. To this end, we need observables of the solar radiation sensitive to the coronal magnetic field. The most familiar observables are the polarization signals of visible and near-infrared forbidden lines of highly ionized species and some ultraviolet permitted lines, like hydrogen Lyα. While the coronal radiation in these spectral lines can only be detected for off-limb lines of sight, the coronal radiation from permitted extreme ultraviolet (EUV) lines can be observed also on the solar disk. These coronal lines are mainly collisionally excited, but it has been pointed out that some permitted EUV lines can actually be linearly polarized if their lower level carries atomic alignment, and that their linear polarization is sensitive to the orientation of the coronal magnetic field . Here we theoretically investigate the linear polarization in permitted EUV lines of a variety of ions: Fe x, Fe xi, Fe xiii, Fe xiv, Si ix, and Si x. To this end, we have developed a numerical code, which we have applied to investigate the linear polarization and magnetic sensitivity of many permitted EUV lines in a one-dimensional model of the solar corona, providing a list of the most promising lines to be further investigated for polarimetry with future space telescopes. Our next step will be to extend this work by using state-of-the-art three-dimensional coronal models.

Galaxy clusters, the largest gravitationally bound structures, host a hot, diffuse plasma with poorly understood viscosity and magnetic field amplification. Astrophysical plasmas are often modeled with magnetohydrodynamics (MHD), but low collision rates in environments such as the intracluster medium (ICM) hinder thermodynamic equilibrium, causing pressure anisotropies and high viscosity. High-β plasmas, dominated by thermal pressure, are prone to instabilities (e.g., firehose or mirror) that limit anisotropy, reduce viscosity, and enable small-scale dynamo-driven magnetic amplification. This study examines viscosity evolution in the ICM during turbulent magnetic field amplification. We performed 3D MHD simulations of forced turbulence with an initially weak, uniform magnetic field. Using the Chew–Goldberger–Low (CGL)-MHD framework, we incorporate anisotropic pressure dynamics and instability-driven anisotropy limitation. We analyze effective viscosity and dynamo evolution, comparing results with Braginskii-MHD and uniform-viscosity MHD. Our results show that viscosity decreases over time, allowing magnetic field amplification to saturation levels similar to nonviscous MHD. Viscosity distribution becomes bimodal, reflecting (i) collisional values and (ii) turbulence-dominated values proportional to 1 × 10⁻⁴L_turbU_turb in unstable regions. At saturation, 60% of plasma retains collisional viscosity. Braginskii-MHD reproduces similar magnetic amplification and viscosity structures. However, uniform-viscosity MHD, where viscosity equals the mean saturated CGL-MHD value, fails to capture the turbulence inertial range. These findings highlight the need for anisotropic viscosity models in studying ICM processes such as magnetic topology, cosmic ray transport, and active galactic nucleus-driven shocks. Moreover, our CGL-MHD and Braginskii-MHD models match the Coma cluster density fluctuation spectrum, reinforcing its weakly collisional nature.

I measure and collect timings of phase markers (like eclipse times) for the orbits of 25 X-ray binaries (XRBs) so as to calculate the steady evolutionary period change (). I combine these with my observed measures from 52 cataclysmic variables (CVs). Further, I subtract out the contributions from gravitational radiation () and mass transfer (), deriving the period change from the residual unknown angular momentum loss ( = ––). I have measures for 77 XRBs and CVs, with these being direct measures of the driver of binary evolution. The venerable magnetic braking model of binary evolution has its most fundamental predictions tested, with most systems having predictions wrong by over 1 order of magnitude. Other proposed mechanisms to explain the angular momentum loss (AML) also fail, so we are left with no known mechanism that dominates the AML. An alternative path to the AML law is empirical, where my measures are fitted to a power law involving the fundamental binary properties. With this, the dominant AML law for systems with orbital periods (P) from 0.13–1.0 day is , in appropriate units. Similar AML laws for binaries below the period gap and for binaries with P > 1.0 day are derived. These three AML laws are of good accuracy and are the best representations of the actual evolution for all 77 XRBs and CVs of all classes, so the three taken together can be called “universal.”

We present a comprehensive study of formaldehyde (H₂CO) absorption and radio recombination line (H_110α) emission in 215 molecular clouds from the Bolocam Galactic Plane Survey, observed using the Nanshan 25 m radio telescope. H₂CO was detected in 88 sources (40.93%) with 59 being new detections, while H_110α emission was found in only 11 sources (5.12%), all coincident with H₂CO absorption. There exists a correlation of H₂CO fluxes with millimeter fluxes below a 3 Jy threshold and an increased dispersion above it, suggesting the sub-cosmic microwave background cooling of H₂CO. Cross-matching with kinematic distance catalogs revealed H₂CO spanning galactocentric distances from 0.216 to 10.769 kpc, with column densities ranging from 7.82 × 10¹¹ to 6.69 × 10¹⁴ cm⁻². A significant inverse correlation was observed between H₂CO detection fraction and galactocentric distance, suggesting enhanced star-forming activity closer to the Galactic Center. These findings challenge traditional Galactic Habitable Zone (GHZ) models by demonstrating the presence of biogenic precursors in the inner Galaxy, shielded within dense molecular clouds. Our results underscore the importance of incorporating chemical tracers such as H₂CO, alongside physical constraints to refine the boundaries of the GHZ and advance the research of prebiotic chemistry in the Milky Way.

In this research, we conducted systematic photometric, spectroscopic, and theoretical modeling analyses of two δ Scuti stars—KIC 12602250 and KIC 5768203—that pulsate only in radial modes. We collected their relevant photometric and spectroscopic parameters from multiple catalogs and estimated the absolute luminosities of both stars. Using high-precision time-series data from Kepler and TESS, we performed in-depth analysis of the periodic modulation in pulsation frequency phases, successfully determining the orbital periods and companion mass distribution ranges for these binary systems. Additionally, we thoroughly investigated the temporal evolution characteristics of pulsation periods and amplitudes. Based on calculations using Modules for Experiments in Stellar Astrophysics stellar evolution models, we determined that KIC 12602250 has a mass of with metallicity and is currently in the main-sequence evolutionary stage. For KIC 5768203, we derived precise parameters through rigorous constraints: mass M = 2.09 ± 0.01M_⊙, metallicity Z = 0.024 ± 0.003, and radius R = 3.19 ± 0.01R_⊙. Theoretical models reveal that this star has already crossed the first main-sequence turn-off point and entered the late-main-sequence evolutionary stage. Through comparative studies with typical High Amplitude δ Scuti stars, we believe that the primary reason for the low radial pulsation amplitudes in these two stars likely stems from their specific evolutionary states.

Theoretical and numerical analyses of the behavior of magnetohydrodynamic (MHD) waves in solar atmospheric structures have a vital role in understanding the plasma dynamics of the Sun. Magneto-helioseismology is indebted to the insight gained from simple magnetic slab structures accompanied by varying conditions within the slab and its environment. This paper builds on the existing literature on these structures by presenting an analytical approach to deriving the dispersion relation for MHD wave propagation in a nonparallel case. Analogous to the parallel case, a plethora of modes emerges that can be classified into quasi-kink or quasi-sausage, body or surface, as well as fast or slow waves. The slab itself can be viewed as thin or wide similarly to previous works, however due to the nonparallel condition it can also be categorised as short or long in the direction of the tilt of the wavevector. This is the analog of the thin or wide slab classification in the parallel direction, expanding our established knowledge regarding propagating MHD waves in magnetic slabs. The variance of the wavenumber along the nonparallel dimension brings to light a number of intriguing features, such as modes changing character with variation of the angle of the wavevector while the propagation speed remains the same. Further new information is provided by the newly derived classification limits, u_±, which act as a form of generalised Alfvén and sound speeds in the dispersion relation.

We investigate the origin of NGC 5634 through a comprehensive analysis of its morphology, kinematics, and dynamics. Utilizing data from the DESI Legacy Survey, we refined its fundamental parameters (age τ = 12.8 ± 0.3 Gyr, metallicity [Fe/H] = −1.8 ± 0.1 dex, distance modulus dm = 17.0 ± 0.1 mag) and constructed a matched-filter template based on the combination of these parameters to search for extra-tidal structures. However, no significant features were detected above a 3σ signal-to-noise threshold, which limits our ability to further investigate the association between NGC 5634 and the Sagittarius (Sgr) stream based on morphological evidence. Incorporating GAIA data, we further examine the orbital path of NGC 5634. We found that its orbit only briefly intersects with the Sgr stream and diverges significantly over long-term integrations. This behavior contrasts with that of confirmed Sgr-associated clusters, whose orbits remain closely aligned with the stream throughout their orbital evolution. Additionally, NGC 5634 exhibits a relatively shorter semimajor axis and smaller apocenter and pericenter distances compared to Sgr clusters. These orbital characteristics are more consistent with clusters associated with the Gaia–Sausage–Enceladus (GSE) or the Helmi streams. From a dynamical perspective, in the L_z–E space, NGC 5634 is also distinctly different from Sgr clusters and aligns more closely with the GSE and Helmi regions. Taken together, these findings do not support a strong connection between NGC 5634 and the Sgr dSph, but instead suggest a potential association with another progenitor system, such as GSE or Helmi stream. Nevertheless, further evidence is needed to definitively establish its origin.

Short large-amplitude magnetic structures (SLAMS) are frequently detected during spacecraft crossings over Earth's bow shock. We investigate the existence of such structures at astrophysical shocks, where they could result from the steepening of cosmic-ray (CR) driven waves. Using kinetic particle-in-cell simulations, we study the growth of SLAMS and the appearance of associated transient shocks in the upstream region of parallel, nonrelativistic, high-Mach-number collisionless shocks. We find that high-energy CRs significantly enhance the transverse magnetic field within SLAMS, producing highly inclined field lines. As SLAMS are advected toward the shock, these field lines form an intermittent superluminal configuration that traps magnetized electrons at fast shocks. Due to their oscillatory nature, SLAMS are periodically separated by subluminal gaps with lower transverse magnetic field strength. In these regions, electrons diffuse and accelerate by bouncing between the shock and the approaching SLAMS' region through a mechanism that we call quasi-periodic shock acceleration (QSA). We analytically derive the distribution of electrons accelerated via QSA, f(p) ∼ p^{[−4.7,−5.7]}, which agrees well with the simulation spectra. We find that the electron power law remains steep until the end of our longest runs, providing a possible explanation for the steep electron spectra observed at least up to GeV energies in young and fast supernova remnants.

We report the observations of a repeating FRB 20230607A for 15.6 hr spanning 16 months using the Five-hundred-meter Aperture Spherical Radio Telescope with the detection of 565 bursts. We present three bright bursts with detailed temporal/spectral structures. We also report that one burst carries a narrow component with a width of only 0.3 ms, which is surrounded by broader components. This suggests that repeaters can make both narrow and broad components in one burst. With the narrow spike, we precisely measure the dispersion measure of 362.85 ± 0.15 pc cm⁻³ and the Faraday rotation measures (RMs) of −12249.0 ± 1.5 rad m⁻². We also analyze the statistical distribution of the burst parameters, including waiting times, temporal widths, central frequencies and frequency widths, fluences and energies, all showing typical distributions of known active repeaters. In particular, most bursts show narrow spectra with Δν/ν₀ = 0.125 ± 0.001. This fact, together with the narrow 0.3 ms spike, strongly suggests a magnetospheric origin of the FRB emission. Based on a predicted correlation between RM and the luminosity of a persistent radio source (PRS) by Yang et al., we predict that the PRS should have a specific luminosity of the order of 10²⁹ erg s⁻¹ Hz⁻¹ and encourage a search for such a PRS.

The geometric distances of active galactic nuclei (AGNs) are challenging to measure because of their exceptionally compact structure, yet vast cosmic distances. A combination of spectroastrometry and reverberation mapping (SARM) of broad-line regions (BLRs) constitutes a novel means to probe the geometric distance of AGNs, which has recently become practically feasible owing to successful interferometric observations with the Very Large Telescope Interferometer/GRAVITY. Here, we perform SARM analysis of four nearby quasars: Mrk 509, PDS 456, 3C 273, and NGC 3783. Results for the former two are reported for the first time, and the latter two are revisited using our improved BLR dynamical modeling that includes the radial-dependent responsivity of BLRs. This allows us to self-consistently account for the emissivity weighting of the BLR in spectroastrometry and responsivity weighting in reverberation mapping. We obtain angular-diameter distances of the four quasars, from which we derive a Hubble constant of . Although this constitutes a large uncertainty for a measurement of H₀, it is anticipated that the precision will improve to a competitive level once a greater number of AGNs are accessible following the upgrade of GRAVITY in the near future. From SARM analysis, the black hole masses of the four quasars are also measured with the statistical uncertainty ranging from 0.06 to 0.23 dex, consistent with the correlations between black hole masses and properties of the host bulges.

We present the results of four 3D radiation magnetohydrodynamic simulations of accretion disks around a 10⁸ solar mass black hole, which produce the far-ultraviolet spectrum peak and demonstrate a robust physical mechanism for producing the extreme-ultraviolet to soft X-ray power-law continuum component. The disks are fed from rotating tori and reach accretion rates ranging from 0.03 to 4 times the Eddington value. The disks become radiation pressure or magnetic pressure dominated, depending on the relative timescales of radiative cooling and gas inflow. Magnetic pressure supported disks can form with or without net poloidal magnetic fields, as long as the inflowing gas can cool quickly enough, which can typically happen when the accretion rate is low. We calculate the emerging spectra from these disks using multigroup radiation transport with realistic opacities and find that they typically peak around 10 eV. At accretion rates close to or above the Eddington limit, a power-law component can appear for photon energies between 10 eV and 1 keV, with a spectral slope varying between L_ν ∝ ν⁻¹ and ν⁻², comparable to what is observed in radio-quiet quasars. A disk with a 3% Eddington accretion rate does not exhibit this component. These high-energy photons are produced in an optically thick region ≈30^∘–45^∘ from the disk midplane, by compressible bulk Comptonization within the converging accretion flow. Strongly magnetized disks that have a very small surface density will produce a spectrum that is very different from what is observed.

Near-infrared spectroscopic surveys target high-redshift emission-line galaxies (ELGs) to probe cosmological scenarios. Understanding the clustering properties of ELGs is essential to derive optimal constraints. We present a simple radiative transfer model for spatially resolved galactic Hα emission, which includes emission from the warm-hot diffuse interstellar medium. The atomic-level populations are in steady state and computed in the coronal approximation. The model is applied to multiple IllustrisTNG simulations in the redshift range 1 ≤ z ≤ 2 to produce the luminosity function (LF) and the halo occupation distribution (HOD). Collisional processes account for a significant fraction (≈40%) of the total Hα luminosity (L_Hα). Our LFs are in reasonable agreement with measurements from Hα surveys if a uniform extinction of 0.3 < A_Hα < 0.85 mag is assumed. Our HOD is consistent with that of the Euclid Flagship galaxy mock up to differences that can be attributed to baryonic feedback, which is absent from the latter. When Hα luminosities are computed from an empirical relation between L_Hα and the total star formation rate, the resulting LFs are in tension with previous observations. Our approach can be extended to other atomic lines, which should be helpful for the mining of high-redshift galaxy spectra in forthcoming surveys.

Stellar streams provide one of the most promising avenues for constraining the global mass distribution of the Milky Way and the nature of dark matter (DM). The stream stars’ kinematic “track” enables inference of large-scale properties of the DM distribution, while density variations and anomalies provide information about local DM clumps (e.g., from DM subhalos). A full accounting of the density tracks and substructures within all >100 Milky Way stellar streams will therefore enable powerful new constraints on DM. Here, we present a new, flexible framework for modeling stellar stream density and membership. With it, one can empirically model a given stream in a variety of coordinate spaces (e.g., on-sky position and velocity) using probability distributions, thereby generating membership probabilities. The most significant improvement over previous methods is the inclusion of off-track or non-Gaussian components to the stream density, meaning we can capture anomalous features (such as the GD-1 steam’s spur). We test our model on GD-1, where we characterize previously known features and provide the largest catalog of probable member stars to date (1689 stars). We then use the derived model to provide measurements of GD-1’s density and kinematic tracks, velocity dispersion, as well as its initial and current mass. Our framework (built on JAX and numpyro) provides a path toward uniform analysis of all Milky Way streams, enabling tight constraints on the Galactic mass distribution and its dark matter.

The chemical composition of galaxies offers vital insights into their formation and evolution. In particular, the relationship between helium abundance (He/H) and metallicity serves as a key diagnostic for estimating the primordial helium yield from Big Bang nucleosynthesis. We investigate the chemical enrichment history of low-metallicity galaxies, focusing especially on extremely metal-poor galaxies (EMPGs), using one-zone chemical evolution models. Adopting elemental yields from M. Limongi & A. Chieffi, our models reach He/H ∼ 0.089 at (O/H) × 10⁵ < 20, yet they fall short of reproducing the elevated He/H values observed in low-redshift dwarf galaxies. In contrast, the observed Fe/O ratios in EMPGs are successfully reproduced using both the K. Nomoto et al. and M. Limongi & A. Chieffi yield sets. To address the helium discrepancy, we incorporate supermassive stars (SMSs) as Population III stars in our models. We find that SMSs can significantly enhance He/H, depending on the mass-loss prescription. When only 10% of the SMS mass is ejected, the model yields the steepest slope in the (O/H) × 10⁵–He/H relation. Alternatively, if the entire outer envelope up to the CO core is expelled, the model can reproduce the high He/H ratios observed in high-redshift galaxies (He/H > 0.1). Additionally, these SMS-enriched models also predict elevated N/O ratios, in agreement with recent JWST observations of the early Universe.

The Lyα Tomography IMACS Survey (LATIS) has produced large 3D maps of the intergalactic medium (IGM), providing a new window on the cosmic web at z ∼ 2.5. A key advantage of Lyα tomography is that it enables the discovery of overdense regions without the need to detect their galaxy members in spectroscopic surveys, circumventing possible selection biases. We use these maps to identify 37 IGM-selected overdensities as regions of strong and spatially coherent Lyα absorption. Simulations indicate that 85% of these are protoclusters, defined as the progenitors of z = 0 halos with mass M_desc > 10¹⁴M_⊙, and that nearly all of the rest are protogroups (10^13.5 < M_desc/M_⊙ < 10¹⁴). We estimate the masses and space densities of the IGM-selected overdensities and show they are in accordance with mock surveys. We investigate the LATIS counterparts of some previously reported protoclusters, including the proto-supercluster Hyperion. We identify a new component of Hyperion beyond its previously known extent. We show that the Lyα transmission of the galaxy density peaks within Hyperion is consistent with a simple physical model (the fluctuating Gunn–Peterson approximation), suggesting that active galactic nucleus feedback or other processes have not affected the large-scale gas ionization within this structure as a whole. The LATIS catalog represents an order-of-magnitude increase in the number of IGM-selected protogroups and protoclusters and will enable new investigations of the connections between galaxies and their large-scale environments at cosmic noon.

We investigate the consistency of intergalactic medium (IGM) tomography and galaxy surveys as tracers of the cosmic web and protoclusters at z ∼ 2.5. We use maps from the Lyα Tomography IMACS Survey (LATIS), which trace the distributions of Lyman-break galaxies (LBGs) and IGM Lyα absorption on ≃4 h⁻¹ cMpc scales within the same large volume. Overall, the joint distribution of IGM absorption and LBG density is well constrained and accurately described by a simple physical model. However, we identify several exceptional locations exhibiting strong IGM absorption indicative of a massive protocluster, yet no coincident overdensity of LBGs. As discussed by Newman et al., whose results we revise using the complete LATIS survey data, these are candidate ultraviolet (UV)-dim protoclusters that may harbor distinct galaxy populations missed by rest-UV spectroscopic surveys. We present follow-up observations targeting one such candidate embedded within Antu, an extended region of IGM absorption at z = 2.685 that contains five IGM-selected protoclusters and has a total mass of 3 × 10¹⁵M_⊙. Lyα emitters trace the overall structure of Antu but avoid the center of the candidate UV-dim protocluster, which also appears to contain no submillimeter-selected sources. A near-infrared spectroscopic galaxy census is needed to determine whether this large region is dominated by galaxies with reduced or absent star formation activity. This work adds to a growing and puzzling literature on discrepancies among different galaxy and IGM tracers, whose resolution promises to shed light on the early stages of environment-dependent galaxy evolution.

The Parker Solar Probe (PSP) mission has revealed frequent occurrences of switchbacks (SBs) and small-scale magnetic flux ropes (SMFRs) as prominent structures within the solar wind. These mesoscale features are observed across all heliocentric distances, with heightened activity in the young solar wind, such as successive SMFRs, blobs, and SBs using PSP in situ observations. One study, in particular, focuses on SMFRs observed during the intervals of PSP corotating with the Sun, which suggests a similar source of the observed solar wind. In this paper, we identified SBs at the boundaries of SMFRs as a regularly observed phenomenon and found instances where SBs and SMFRs co-occur, with the significance level α < 0.05. The SMFR-related SBs—observed at the leading and trailing edges of an SMFR—exhibit well-organized axial co-orientations, with their polarity flipping, meaning the radial direction remains constrained while the transversal field reverses. Furthermore, the axial field directions of SMFR-related SBs appear to be more closely connected than to another SB that is spatially closer and are linked to the SMFR orientation. Our analysis of their relative geometry, which examines the alignment between SBs and the SMFR axis, reveals a distinct tendency emphasizing their correlation, further supporting the idea that the axes of SMFR-related SBs are presumably determined by the SMFR orientation. Observations suggest that a fraction of SBs are spatially and temporally associated with SMFRs, implying that processes related to SMFR boundaries may contribute to SB formation or that SBs tend to develop in magnetic environments shaped by SMFRs.

Phase mixing has long been understood to be a viable mechanism for expediting the dissipation of Alfvén wave energy resulting in the subsequent heating of the solar atmosphere. To fulfill the conditions necessary for phase mixing to occur, we consider the cross-field gradient in the Alfvén speed as a free parameter in our model. Using a single-fluid description of a partially ionized chromospheric plasma, we explore the efficiency of damping of shear Alfvén waves subject to phase mixing when a pulse wave driver is employed. Our results demonstrate a strong dependence of the dissipation length of shear Alfvén waves on both the ionization degree of the plasma and the gradient of the Alfvén speed. When assessing the efficiency of phase mixing across various inhomogeneities, our findings indicate that waves originating from a pulse driver initially exhibit heating rates identical to those generated by a continuous wave driver. One key difference observed was that Alfvén pulses possess a lower overall decay rate, due to a change in damping profile from exponential to algebraic. This discrepancy arises from the absence of a consistent injection of energy into the base of the domain, which preserves longitudinal gradients of the magnetic field perturbations more effectively. These findings demonstrate the importance of understanding the relations between the wave driver, damping mechanisms, and propagation dynamics in resolving the atmospheric heating problem.

White dwarfs (WD) with main-sequence (MS) companions are crucial probes of stellar evolution. However, due to the significant difference in their luminosities, the WD is often outshined by the MS star. The aim of this work is to find hidden companions in Gaia’s sample of WD candidates. Our methodology involves applying an unsupervised machine learning algorithm for dimensionality reduction and clustering, known as a self-organizing map (SOM), to Gaia BP/RP (XP) spectra. This strategy allows us to naturally separate WDMS binaries from single WDs from the detection of subtle red flux excesses in the XP spectra that are indicative of low-mass MS companions. We validate our approach using confirmed WDMS binaries from the Sloan Digital Sky Survey and LAMOST surveys, achieving a precision of ∼90%. We demonstrated that the luminosity of the faint companions in the missed systems is ∼50 times lower than that of their WD primaries. Applying our SOM to 90,667 sources, we identify 993 WDMS candidates, 506 of which have not been previously reported in the literature. If confirmed, our sample will increase the known WDMS binaries by 20%. Additionally, we use the Virtual Observatory Spectral Energy Distribution Analyzer tool to refine and parameterize a “golden sample” of 136 WDMS binaries through multiwavelength photometry and a two-body spectral energy distribution fitting. These high-confidence WDMS binaries are composed of low-mass WDs (∼0.42M_⊙), with cool MS companions (∼2800 K). Finally, 13 systems exhibit periodic variability consistent with eclipsing binaries, making them prime targets for further follow-up observations.

It has long been known that a large population of Be/X-ray binaries (BeXRBs) exists in the Milky Way’s neighboring dwarf galaxy, the Small Magellanic Cloud (SMC), due to a recent period of intense star formation. Since 2016, efforts have been made to monitor this population and identify new BeXRBs through the Swift SMC Survey (S-CUBED). S-CUBED’s weekly observation cadence has identified many new BeXRBs that exist within the SMC, but evidence suggests that more systems exist that have thus far escaped detection. A major challenge in identifying new BeXRBs is their transient nature at high-energy wavelengths, which prevents them from being detected via their X-ray emission characteristics when not in outburst. In order to identify sources that may have been missed owing to a long period of quiescence, it becomes necessary to devise methods of detection that rely on wavelengths at which BeXRBs are more persistent emitters. In this work, we attempt to use archival analysis of infrared, optical, and ultraviolet observations to identify new candidate BeXRBs that have been overlooked within the S-CUBED source catalog. Using X-ray/optical selection of source properties, unsupervised clustering, spectral energy distribution fitting to VizieR archival measurements, and ultraviolet light-curve analysis, we are able to identify six new candidate BeXRB systems that otherwise would have been missed by automated analysis pipelines. Using these results, we demonstrate the use of ultraviolet through near-infrared observational data in identifying candidate BeXRBs when they cannot be identified using their X-ray emission.

Brown dwarfs provide a unique opportunity to study atmospheres and their physical and chemical processes with high precision, especially in temperature ranges relevant to exoplanets. In this study, we performed high-resolution (R ∼ 70,000) spectroscopy using Subaru/IRD (Y, J, H bands) of the T7.0p-type object Gl 229 B, the first discovered T-type brown dwarf, which orbits an M1V host star at a separation of 33 au. We conducted atmospheric retrieval on the reduced H-band spectrum using the high-resolution spectrum model compatible with automatic differentiation and GPU, ExoJAX. In contrast to previous retrieval studies on medium-resolution spectra, we obtained a C/O ratio consistent with that of the host star, aligning with the expected formation process for such a massive brown dwarf. Additionally, based on the strong constraint on temperature from the high-resolution spectrum and previously measured photometric magnitude, our analysis indicates that Gl 229 B is a binary, which was also proposed by G. M. Brandt et al. and recently confirmed by J. W. Xuan et al. Finally, we validated current molecular line lists by leveraging the obtained high-resolution, high signal-to-noise ratio spectrum of this warm (∼900 K) atmosphere. This study highlights the importance of observing companion brown dwarfs as benchmark objects for establishing characterization techniques for low-mass objects and enhancing our understanding of their atmospheres, given the wealth of available information and the relative ease of observation.

Recent analyses of cosmological hydrodynamic simulations from CAMELS have shown that machine learning models can predict the parameter describing the total matter content of the universe, Ω_m, from the features of a single galaxy. We investigate the statistical properties of two of these simulation suites, IllustrisTNG and ASTRID, confirming that Ω_m induces a strong displacement on the distribution of galaxy features. We also observe that most other parameters have little to no effect on the distribution, except for the stellar-feedback parameter A_SN1, which introduces some near-degeneracies that can be broken with specific features. These two properties explain the predictability of Ω_m. We use optimal transport to further measure the effect of parameters on the distribution of galaxy properties, which is found to be consistent with physical expectations. However, we observe discrepancies between the two simulation suites, both in the effect of Ω_m on the galaxy properties and in the distributions themselves at identical parameter values. Thus, although Ω_m’s signature can be easily detected within a given simulation suite using just a single galaxy, applying this result to real observational data may prove significantly more challenging.

We present an analysis of millimeter CO observations to search for and quantify signatures of molecular gas outflows. We exploit the large sample of 0.5 < z < 2.6 galaxies observed as part of the PHIBSS1/2 surveys with the IRAM Plateau de Bure interferometer, focusing on the 154 typical massive star-forming galaxies with CO detections (mainly CO(3–2), but including also CO(2–1) and CO(6–5)) at signal-to-noise ratio (SNR) > 1.5 and available properties (stellar mass, star formation rate or SFR, size) from ancillary data. None of the individual spectra exhibit a compelling signature of CO outflow emission, even at high SNR > 7. To search for fainter outflow signatures, we carry out an analysis of stacked spectra, including the full sample, as well as subsets, split in terms of stellar mass, redshift, inclination, offset in SFR from the main sequence, and active galactic nuclei activity. None of the physically motivated subsamples shows any outflow signature. We report a tentative detection in a subset statistically designed to maximize outflow signatures. We derive upper limits on molecular gas outflow rate and mass loading factors η based on our results and find η ≤ 2.2–35.4, depending on the subsample. Much deeper CO data and observations of alternative tracers are needed to decisively constrain the importance of the cold molecular gas component of outflows relative to other gas phases.

Angular momentum transport by magnetic fields is important for formation and evolution of protoplanetary disks. The effects of magnetic fields are suppressed due to nonideal magnetohydrodynamic (MHD) effects such as ambipolar diffusion and Ohmic dissipation, which depend on the degree of ionization. Cosmic rays (CRs) are the primary source of ionization in star-forming clouds, and their distribution is nonuniform as it is affected by gas density and magnetic fields. Therefore, CRs, magnetic fields, and gas interact with each other. In this work, we develop a new fully implicit CR transport module in Athena++ and perform 3D simulations of disk formation from collapse of molecular cloud cores. Since CRs are strongly attenuated in the dense gas at the disk scale, distribution of magnetic fields is considerably altered compared to conventional models assuming a uniform ionization rate. While the total magnetic fluxes accreted onto the disks remain similar as the gas outside the disks remains sufficiently ionized and well coupled, the magnetic fields in the disks are less twisted due to the stronger nonideal MHD effects. As a consequence, magnetic angular momentum transport is strongly suppressed at the disk scale, resulting in more gravitationally unstable disks with more prominent spiral arms. Our simulations demonstrate the influence of nonuniform ionization resulting from CR transport and attenuation on the disk formation and evolution.

The unprecedented sensitivity of the James Webb Space Telescope (JWST) has uncovered a surprisingly abundant population of mildly obscured, low-luminosity active galactic nuclei (AGNs) in the epoch of reionization (EoR). However, the link between these objects and classical unobscured quasars remains a mystery. Here we report the discovery of obscured quasars hosted by the most luminous galaxies at z > 6, possibly bridging the gap between the two AGN populations. The 13 objects presented here were originally selected from a rest-frame ultraviolet (UV) imaging survey over >1000 deg², and were known to have luminous (>10⁴³ erg s⁻¹) Lyα emission. With JWST/NIRSpec follow-up observations, we found that 7 out of 11 objects with narrow Lyα exhibit a broad component in H I Balmer lines and He I lines, but not in [O III] and other forbidden lines. Mild dust obscuration (0 < A_V < 3) is inferred from the Balmer decrements. The estimated intrinsic luminosities suggest that our broad-line (BL) objects are the long-sought UV-obscured counterparts of luminous quasars in the EoR. They host supermassive black holes (SMBHs) with masses 10^7.8−9.1M_⊙, undergoing sub-Eddington to Eddington accretion. Most of the BL objects are spatially unresolved and are close to “little red dots” with their blue rest-UV and red rest-optical colors. We estimate the AGN number density among similarly luminous Lyα emitters to be larger than 2 × 10⁻⁸ Mpc⁻³. This density is comparable to that of classical quasars with similar continuum luminosities, suggesting that a substantial fraction of active SMBHs are obscured in the EoR and have been overlooked in past rest-UV surveys.

We here report the results from spectroscopic observations of a sample of 26 globular cluster (GC) and 21 faint fuzzy (FF) candidates in the lenticular galaxy NGC 1023 using the 10.4 m Gran Telescopio Canarias. Using the recessional velocities and stellar absorption features, we determine that 18 and 9 of the observed candidates are bona fide GCs and FFs, respectively. The majority of the rejected FF candidates are background emission line galaxies for which we determine their redshifts. We used the spectroscopic data to determine velocity, age, metallicity, and extinction of all bona fide clusters. We find that FFs are clearly younger (age = 7–9 Gyr) than GCs (age > 10 Gyr). Both kinds of clusters in this galaxy are metal-rich ([Fe/H] = −0.58 ± 0.33). The ages and metallicities of individual FFs reported here are the first such measurements in any galaxy and agree with the previously reported measurement on stacked spectrum. The kinematical analysis reaffirms that the FFs belong to the disk of the galaxy, suggesting that their progenitors are most likely massive, compact disk clusters that have been able to survive for long timescales. We propose that the fuzzy appearance of FFs as compared to the GCs is a consequence of the dynamical evolution of their progenitor super star clusters in the disks of low-mass galaxies.

Quasars are bright active galactic nuclei powered by the accretion of matter around supermassive black holes at the center of galaxies. Their stochastic brightness variability depends on the physical properties of the accretion disk and black hole. The upcoming Rubin Observatory Legacy Survey of Space and Time (LSST) is expected to observe tens of millions of quasars, so there is a need for efficient techniques like machine learning that can handle the large volume of data. Quasar variability is believed to be driven by an X-ray corona, which is reprocessed by the accretion disk and emitted as UV/optical variability. We are the first to introduce an auto-differentiable simulation of the accretion disk and reprocessing. We use the simulation as a direct component of our neural network to jointly model the driving variability and reprocessing, trained with supervised learning on simulated LSST-like 10 yr quasar light curves. We encode the light curves using a transformer encoder, and the driving variability is reconstructed using latent stochastic differential equations, a physically motivated generative deep learning method that can model continuous-time stochastic dynamics. By embedding the physical processes of the driving signal and reprocessing into our network, we achieve a model that is more robust and interpretable. We demonstrate that our model outperforms a Gaussian process regression baseline and can infer accretion disk parameters and time delays between wave bands, even for out-of-distribution driving signals. Our approach provides a powerful framework that can be adapted to solve other inverse problems in multivariate time series.

The binarity of red supergiants (RSGs) influences their evolution and the fate of supernovae. We investigate the binary fraction of RSGs in the Andromeda galaxy (M31) and Triangulum galaxy (M33) using photometry from the Hubble Space Telescope (HST), which offers high spatial resolution to resolve more RSGs. A preliminary step involves identifying a reliable and complete RSG sample using the F110W − F160W versus F160W diagram, yielding 2612 RSGs from the Panchromatic Hubble Andromeda Treasury (PHAT) survey of M31 and 3294 RSGs from the Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region survey of M33. These samples suggest total RSG populations in M31 and M33 of 6563 and 7572, respectively. These estimates significantly exceed previous ones from the ground-based observations, an increase attributed to the superior spatial resolution of the HST. The stellar parameters of these RSGs, including effective temperature (T_eff), radius (R), and luminosity (L), are derived by fitting their spectral energy distribution (SED) across optical and near-infrared bands. Binary candidates are identified by detecting ultraviolet excesses in their SEDs compared to the single-star RSG model prediction. The binary fraction is determined to be 33.4% ± 0.9% for M31 and 30.9% ± 0.8% for M33. For more luminous RSGs with log L/L_⊙ > 4.0, the binary fraction decreases to 31.6% ± 1.9% in M31 and increases to 34.7% ± 1.8% in M33, respectively. These results are in good agreement with predictions from the Binary Population and Spectral Synthesis binary evolution model.

We present photometric and spectroscopic observations of supernova SN 2023ixf covering from day 1 to 442 days after explosion. SN 2023ixf reached a peak V-band absolute magnitude of −18.2 ± 0.07, and light curves show that it has a relatively short “plateau” phase (∼72 days), and can be classified either as an SN IIL or a transitional event between IIP and IIL. Early-time spectra of SN 2023ixf exhibit strong, very narrow emission lines from ionized circumstellar matter (CSM), possibly indicating a Type IIn classification. But these flash/shock-ionization emission features faded after the first week and the spectrum evolved in a manner similar to that of typical Type II SNe, unlike the case of most genuine SNe IIn in which the ejecta interact with CSM for an extended period of time and develop intermediate-width emission lines. We compare observed spectra of SN 2023ixf with various model spectra to understand the physics behind SN 2023ixf. Our nebular spectra (between 200 and 400 days) match best with the model spectra from a 15 M_⊙ progenitor that experienced enhanced mass loss a few years before explosion. A last-stage mass-loss rate of from the r1w6 model matches best with the early-time spectra, higher than derived from the ionized Hα luminosity at 1.58 days. We also use SN 2023ixf as a distance indicator and fit the light curves to derive the Hubble constant by adding SN 2023ixf to the existing sample; we obtain km s⁻¹ Mpc⁻¹, consistent with the results from SNe Ia and many other independent methods.

The nondetection of periodicity related to rotation challenges magnetar models for fast radio bursts (FRBs) with FRB emission from close to the magnetar surface. Moreover, a bimodal distribution of the burst waiting times is widely observed in hyperactive FRBs, a significant deviation from the exponential distribution expected from stationary Poisson processes. By combining the epidemic-type aftershock sequence earthquake model and the rotating vector model involving the rotation of the magnetar and orientations of the spin and magnetic axes, we find that starquake events modulated by the rotation of FRB-emitting magnetar can explain the bimodal distribution of FRB waiting times, as well as the nondetection of periodicity in hyperactive repeating FRBs. We analyze data from multiple FRB sources, demonstrating that differences in waiting time distributions, and to some extent, observed energies can be explained by varying parameters related to geometric properties of the magnetar FRB emission and starquake dynamics. Our results show that the assumption that all FRBs are repeaters is compatible with our model. Notably, we find that hyperactive repeaters tend to have small magnetic inclination angles in order to hide their periodicity. We also show that our model can reproduce the waiting time distribution of a pulsar phase of the galactic magnetar SGR J1935+2154 with a larger inclination angle than the hyperactive repeaters, which could explain the detection of spin period and the relatively low observed energy for FRBs from the magnetar. The spin periods of hyperactive repeaters are not well constrained, but most likely fall in the valley region between the two peaks of the waiting time distributions.

Planets, especially those close to their host stars, lose mass to atmospheric outflows, a process that is thought to shape the bimodal population of gaseous giant and rocky terrestrial exoplanets in close orbits. We model the hydrodynamic escape of planetary atmospheres in idealized, three-dimensional gas dynamic simulations in order to study their emergent morphology. As we vary the simulated system parameters, model outflows show a range of shapes from fast, isotropic outflows bounded by bow shocks to slower motion confined to thin streams. We show that a crucial factor is the role of the tidal gravity and orbiting reference frame in which planets lose mass. Flows can be characterized by the dimensionless Rossby number evaluated at the scale of the Hill sphere. Flows with a low Rossby number are significantly deviated and shaped by the stellar gravity, while those with a high Rossby number are comparatively unaffected. Rossby number alone is sufficient to predict outflow morphology as well as kinematic gradients across transit. Hydrodynamic outflows from the known exoplanet population should span a range of outflow Rossby numbers and therefore exhibit a range of morphologies. In realistic systems, shaping from gravity and hydrodynamics alone can be supplemented by the effects of stellar-wind collisions and magnetic stresses.

We present a novel tensor network algorithm to solve the time-dependent, gray thermal radiation transport equation. The method invokes a tensor train (TT) decomposition for the specific intensity. The efficiency of this approach is dictated by the rank of the decomposition. When the solution is “low rank,” the memory footprint of the specific intensity solution vector may be significantly compressed. The algorithm, following a step-then-truncate approach of a traditional discrete ordinates method, operates directly on the compressed state vector, thereby enabling large speedups for low-rank solutions. To achieve these speedups, we rely on a recently developed rounding approach based on the Gram-SVD. We detail how familiar S_N algorithms for (gray) thermal transport can be mapped to this TT framework and present several numerical examples testing both the optically thick and thin regimes. The TT framework finds low-rank structure and supplies up to ≃60× speedups and ≃1000× compressions for problems demanding large angle counts, thereby enabling previously intractable S_N calculations and supplying a promising avenue to mitigate ray effects.

We present a simulation of the time-domain catalog for the Nancy Grace Roman Space Telescope’s High-Latitude Time-Domain Core Community Survey. This simulation, called the Hourglass simulation, uses the most up-to-date spectral energy distribution models and rate measurements for 10 extragalactic time-domain sources. We simulate these models through the design reference Roman Space Telescope survey: four filters per tier, a five-day cadence, over 2 yr, a wide tier of 19 deg², and a deep tier of 4.2 deg², with ∼20% of those areas also covered with prism observations. We find that a science-independent Roman time-domain catalog, assuming a signal-to-noise ratio at a max of >5, would have approximately 21,000 Type Ia supernovae, 40,000 core-collapse supernovae, around 70 superluminous supernovae, ∼35 tidal disruption events, three kilonovae, and possibly pair-instability supernovae. In total, Hourglass has over 64,000 transient objects, 11,000,000 photometric observations, and 500,000 spectra. Additionally, Hourglass is a useful data set to train machine learning classification algorithms. We show that SCONE is able to photometrically classify Type Ia supernovae with high precision (∼95%) to a z > 2. Finally, we present the first realistic simulations of non-Type Ia supernovae spectral time series data from Roman’s prism.

TOI-2109b is the ultra-hot Jupiter with the shortest orbital period (∼16 hr) yet discovered. At this close distance, strong tidal interactions can produce a significant exchange of angular momentum with the star. Since the orbital period of this planet is shorter than the stellar rotation period, TOI-2109b may be an optimal candidate for studying orbital decay. This process depends on how efficiently the star and the planet dissipate energy, due mainly to interior mechanisms that are poorly constrained in exoplanet systems. In this work, we study for the first time the tidal evolution of TOI-2109b under a formalism of inertial waves (IWs) in convective envelopes and internal gravity waves (IGWs) in stellar radiative regions. We find that uncertainties in the age of TOI-2109 (t_⋆,age) significantly affect the rate of orbital evolution, as IWs and IGWs interact differently depending on t_⋆,age. For an “old” host star, we find that TOI-2109b would undergo fast orbital decay. Conversely, if TOI-2109b orbits a “young” host star, a rather slow decay rate for would suggest a constant-period orbit. Our calculated mid-transit times and transit-timing variations (TTVs) support a “young” host star with , suggesting a decay rate that could lead to mid-transit-time shifts ≲10 s over three years. Orbital decay and other TTV-inducing effects will be confirmed or ruled out with future higher-quality timing data. The results presented here aim at constraining the current modeling of tides and TTVs for TOI-2109b, helping us further understand light-curve changes associated with the long-term evolution of ultra-short-period planets.

Suprathermal electrons are routinely observed in interplanetary space. At higher energies, there are in-situ evidences that shocks, both interplanetary shocks, often driven by fast coronal mass ejections, and terrestrial bow shocks, can accelerate electrons up to transrelativistic energies (∼MeVs). The acceleration mechanism responsible for these energetic electrons is still under debate. In this work, we study the effects of large-scale shock ripples on electron acceleration at a quasi-perpendicular shock in a 2D system. For tractability of the numerical simulation, we consider the scenario where the magnetic field line contains ripples, and the shock is assumed planar and piecewise. The propagation of gyrophase-averaged electrons is governed by the focused transport equation, where the effect of the turbulent magnetic field is modeled by the pitch-angle diffusion, described by the quasi-linear theory. A Monte Carlo simulation on the equivalent time-forward Itô stochastic differential equation is performed within a periodic box to obtain the phase-space distribution function of the accelerated electrons. Our model predicts power-law energy spectra with a cutoff at high-energy ends, whereas their spectral indices are softer than those predicted by the diffusive shock acceleration theory. We demonstrate that, with a suitable choice of pitch-angle diffusion strength, a small fraction of electrons can experience magnetic traps in multiple ripples along the shock surface, boosting their energies to ∼MeVs. Our results therefore provide a framework for a better understanding of relativistic electron events associated with shocks within the heliosphere.

The central supermassive black hole (SMBH) of the Andromeda galaxy, known as M31*, exhibits dim electromagnetic emission and is inferred to have an extremely low accretion rate for its remarkable mass (∼10⁸M_⊙). In this work, we use three-dimensional hydrodynamical simulations to explore a previously untested scenario, in which M31* is fed by the collective stellar mass loss from its surrounding nuclear star cluster, manifested as a famous eccentric disk of predominantly old stellar populations. The stellar mass loss is assumed to be dominated by the slow and cold winds from 100 asymptotic giant-branch stars, which follow well-constrained Keplerian orbits around M31* and together provide a mass injection rate of ∼4 × 10⁻⁵M_⊙ yr⁻¹. The simulations achieve a quasi-steady state on a megayear timescale, at which point a quasi-Keplerian, cool (T ∼ 10³–10⁴ K) gas disk extending several parsecs is established. This disk is continuously supplied by the stellar winds and itself feeds the central SMBH. At the end of the simulations at 2 Myr, an accretion rate of ∼2 × 10⁻⁵M_⊙ yr⁻¹ is found but could vary by a factor of a few depending on whether the subdominant gravity of the NSC or a moderate global inflow is included. The predicted X-ray luminosity of ∼10³⁶ erg s⁻¹, dominated by the hot (T ∼ 10⁷–10⁸ K) plasma within 0.2 pc of the SMBH, is consistent with Chandra observations. We conclude that the feeding mechanism of M31* is successfully identified, which has important implications for the working of dormant SMBHs prevalent in the local Universe.

The circumgalactic medium (CGM) is poorly constrained at the subparsec scales relevant to turbulent energy dissipation and regulation of multiphase structure. Fast radio bursts are sensitive to small-scale plasma density fluctuations, which can induce multipath propagation (scattering). The amount of scattering depends on the density fluctuation spectrum, including its amplitude , spectral index β, and dissipation scale l_i. We use quasar observations of CGM turbulence at ≳pc scales to infer , finding it to be m^−20/3 for hot (T > 10⁶ K) gas and m^−20/3 for cool (10⁴ ≲ T ≲ 10⁵ K) gas, depending on the gas sound speed and density. These values of are much smaller than those inferred in the interstellar medium at similar physical scales. The resulting scattering delays from the hot CGM are negligible (≪1 μs at 1 GHz), but they are more detectable from the cool gas as either radio pulse broadening or scintillation, depending on the observing frequency and sightline geometry. Joint quasar-FRB observations of individual galaxies can yield lower limits on l_i, even if the CGM is not a significant scattering site. An initial comparison between quasar and FRB observations (albeit for different systems) suggests l_i ≳ 750 km in ∼10⁴ K gas in order for the quasar and FRB constraints to be consistent. If a foreground CGM is completely ruled out as a source of scattering along an FRB sightline, then l_i may be comparable to the smallest cloud sizes (≲pc) inferred from photoionization modeling of quasar absorption lines.

In this work, we determine the total globular cluster (GC) counts and globular cluster system (GCS) total mass estimates for 27 extremely massive elliptical galaxies. The GC 2D spatial distributions of these galaxies were created from photometry of Hubble Space Telescope images using DOLPHOT in the near-IR wavelength range. The projected radial density profiles of these GCSs were determined using a Voronoi-tessellation-based technique introduced in our previous paper. We then plot these galaxies on the GCS–halo mass relation alongside previously studied galaxies in the literature. The relation now extends across seven decades of halo mass. We find that the 1:1 slope of this relation holds out to the highest-mass galaxies, although extremely massive BCG galaxies are shifted to higher GCS masses than their lower-mass galaxy counterparts. We find a negative correlation with massive galaxies’ offset from the GCS–halo mass relation and the steepness of their GCS density profiles, and that this is being driven by the red GC populations. We suggest that the biggest influence in intrinsic scatter in the GCS–halo mass relation for massive galaxies is through a few major mergers resulting in accretion of massive satellites with old, red GC populations, rather than many accretions of small satellites with younger, blue GC populations.

To understand the presence of the supervirial temperature gas detected in the Milky Way (MW), we present our findings from isolated galaxy simulations of MW-mass systems using GIZMO with the Feedback in Realistic Environments (FIRE-2) stellar feedback model. It unveils the presence of a significant supervirial temperature (T > T_vir) gas component within 20 kpc from the galactic center. We also find that 70%–90% of the total supervirial gas is extraplanar, at 1 < z < 6 kpc and R_cyl < 15 kpc. This supervirial gas has a mass of 1−2 × 10⁷M_⊙ with typical gas densities are 10^−3.5−10^−2.5 cm⁻³. We find that some of the virial gas (T ∼ 10⁶ K) forms a rotating hot inflow, where gravitational energy is converted to thermal energy mainly via compressive heating. This process causes gas falling close to the rotation axis to reach supervirial temperatures via a combination of compressive heating and shocks just before cooling and joining the disk. Stellar feedback heating accounts for less than 1% of the supervirial gas, indicating its minimal influence despite expectations. Even in scenarios with no stellar feedback effects considered, abundant supervirial gas persists, highlighting the dominance of alternative heating mechanisms. We also show that cosmic rays do not have a significant effect on heating the gas to a supervirial temperature. Our study illuminates the intricate dynamics of hot virial and supervirial gas surrounding MW-mass galaxies, emphasizing the prominent role of infall-driven compressive and shock-heating processes in shaping thermal evolution.

We present new CO(2–1) observations (resolution ∼1″ = 460 pc) of the Coma cluster jellyfish galaxy NGC 4858 obtained from the ALMA-JELLY large program. Analyzing this data alongside complimentary Subaru Hα and Hubble Space Telescope (F600LP / F350LP) observations, we find numerous structural and kinematic features indicative of the effects from strong, inclined ram pressure, including an asymmetric inner gas tail. We estimate a highly inclined disk-wind angle of . By subtracting a simple circular velocity model, we find (1): gas clumps that are being accelerated by ram pressure, and (2): signatures of gas clumps that had been previously pushed out of the disk but are now falling inward. We also discuss head-tail morphologies in star complexes within the stellar disk that appear to be ram pressure stripping (RPS)-influenced. Lastly, we compare this galaxy to state-of-the-art galaxy “wind tunnel” simulations. We find that this galaxy is one of the best nearby examples of strong and inclined ram pressure gas stripping, and of gas that is perturbed by ram pressure but not fully stripped and falls back. We emphasize the importance of torques due to ram pressure in highly inclined interactions, which help drive gas inward on the side rotating against the wind, contributing to the formation of asymmetric inner RPS tails.

Early JWST photometric studies discovered a population of UV-faint () z ∼ 6.5–8 Lyman break galaxies with spectral energy distributions implying young ages (∼10 Myr) yet relatively weak Hβ + [O iii] equivalent widths (EW_{Hβ + [O iii]} ≈ 400 Å). These galaxies seemingly contradict the implicit understanding that young star-forming galaxies are ubiquitously strong Hβ + [O iii] emitters, i.e., extreme emission line galaxies (EW ≳750 Å). Low metallicities, high Lyman continuum escape fractions, and rapidly declining star formation histories have been proposed as primary drivers behind low Hβ + [O iii] EWs, but the blend of Hβ + [O iii] in photometric studies makes proving one of these scenarios difficult. We aim to characterize this peculiar population with deep spectroscopy from the JWST Advanced Deep Extragalactic Survey. We find that a significant subset of these galaxies at z ≳ 2 with modest Hβ + [O iii] EWs (≈300–600 Å) have high ionization efficiencies (). Suppressed [O iii] EW values yet elevated Hα and Hβ EW values imply that the level of chemical enrichment is the primary culprit, supported by spectroscopic measurements of metallicities below 12 + log(O/H) ≈ 7.70 (0.1Z_⊙). We demonstrate that integrated Hβ + [O iii] selections (e.g., Hβ + [O iii] EW > 700 Å) exclude the most metal-poor efficient ionizers and favor (1) more chemically enriched systems with comparable extreme radiation fields and (2) older starbursting systems. In contrast, metallicity degeneracies are reduced in Hα space, enabling the identification of these metal-poor efficient ionizers by their specific star formation rate.

Between 2017 and 2024, the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory has observed numerous white-light solar flares (WLFs). HMI spectropolarimetric observations of certain WLFs, in particular the X9.3 flare of 2017 September 6, reveal one or more locations within the umbra or along the umbra/penumbra boundary of the flaring active region where the Fe I 6173 Å line briefly goes into full emission, indicating significant heating of the photosphere and lower chromosphere. For five flares featuring Fe I 6173 Å line-core emission, we perform spectropolarimetric analysis using HMI 90 s cadence Stokes data. For all investigated flares, line-core emission is observed to last for a single 90 s frame and is either concurrent with or followed by an increase in the line continuum intensity lasting one to two frames (90–180 s). Additionally, permanent changes to the Stokes Q, U, and/or V profiles were observed, indicating long-lasting nontransient changes to the photospheric magnetic field. These emissions coincided with local maxima in hard X-ray emission observed by Konus-Wind, as well as local maxima in the time derivative of soft X-ray emission observed by GOES 16-18. Comparison of the Fe I 6173 Å line profile synthesis for the ad hoc heating of the initial empirical VAL-S umbra model and quiescent-Sun (VAL-C-like) model indicates that the Fe I 6173 Å line emission in the white-light flare kernels could be explained by the strong heating of initially cool photospheric regions.

We use data from the Evolutionary Map of the Universe (EMU) and Polarization Sky Survey of the Universe’s Magnetism (POSSUM) radio southern sky surveys, conducted with the Australian Square Kilometre Array Pathfinder (ASKAP) to compile a catalog of Galactic supernova remnants (SNRs) and candidate SNRs within the region of 2775 ≤ ℓ ≤ 3117 Galactic longitude, ∣b∣ ≤ 54 Galactic latitude, as well as an additional field along the Galactic plane, approximately 3155 ≤ ℓ ≤ 3230 Galactic longitude, −4.5 ≤ b ≤ 1.5 Galactic latitude. In the areas studied, there are 44 known SNRs and 46 SNR candidates that have been previously identified in the radio. We confirm eight of these candidates as SNRs based on evidence of linear polarization or through the calculation of nonthermal spectral indices. Additionally, we identify possible radio counterparts for seven SNR candidates that were previously only identified in X-rays (four) or optical (three). We also present six new SNRs and 37 new SNR candidates. The results of this study demonstrate the utility of ASKAP for discovering new and potential SNRs and refining the classification of previously identified candidates. In particular, we find that the EMU and POSSUM surveys are particularly well suited for observing high-latitude SNRs and confirming SNR candidates with polarization. The region studied in this work represents approximately one-quarter of the Galactic plane, by longitude, that will eventually be surveyed by EMU/POSSUM, and we expect that the ongoing surveys will continue to uncover new SNRs and SNR candidates.

We statistically analyze the power spectral density (PSD) of magnetic field turbulence in the upstream solar wind of the Martian bow shock by investigating the data from Tianwen-1 and Mars Atmosphere and Volatile Evolution (MAVEN) during 2021 November 13 and December 31. The spectral indices and break frequencies of these PSDs are automatically identified. According to the profiles of the PSDs, we find that they could be classified into three types: A, B, and C. Only less than a quarter of the events exhibit characteristics similar to the 1 au PSDs (Type A). We observe the energy injection in more than one-third of the events (Type B), and the injected energy usually results in the steeper spectral indices of the dissipation ranges. We find the absence of the dissipation range in over one third of the PSDs (Type C), which is likely due to the dissipation occurring at higher frequencies rather than proton cyclotron resonant frequencies. We also find that the two spacecraft observed different types of PSDs in more than half of the investigated episodes, indicating significant variability upstream of the Martian bow shock. For example, the Type-B PSDs are more often seen by Tianwen-1, which was near the flank of the bow shock, than by MAVEN near the nose. This statistical study demonstrates the complicated turbulent environment of the solar wind upstream of the Martian bow shock.

We present a newly appreciated FU Ori outburst event that began in 2019 and reached a peak in early 2021. Suspected young stellar object WISE J054452.25+333009.6 experienced substantial brightening, in excess of −5 mag at optical wavelengths and −2.5 mag at mid-infrared wavelengths. The time from near-quiescence to peak brightness was approximately 24 months. Optical and near-infrared spectra confirm that the outbursting source (hereby designated FUOr-Aur 0544+3330) shows all the hallmarks of the FU Ori class, including the Li i indicator of stellar youth. The mix of ionized and neutral atomic lines, alongside prominent molecular absorption features, is consistent with the expected change in spectral type from earlier in the optical to later types in the near-infrared. The closest analog among well-studied FU Ori objects is V1515 Cyg. Both sources have unusually narrow-lined absorption spectra that can be explained by a face-on disk orientation, such that disk-broadening is minimized and wind-induced blueshift (in e.g., Hα, NaD, Ca ii) is maximized. Both the optical through infrared spectral energy distribution and high-resolution spectrum are well-fit by a pure-accretion disk model. Adopting a distance of d = 1.5 kpc, the accretion and central star parameters are M_⊙ yr⁻¹, M_* = 0.17 M_⊙, and R_inner = 1.04 R_⊙. Other fitted values are disk inclination i = 5.9 deg and source extinction A_V = 1.83 mag. These parameters yield accretion luminosity L_acc = 8.4 L_⊙ and maximum disk temperature K.

Based on well-grounded Galactic neutron star populations formed from radio pulsar population syntheses of canonical pulsars (CPs) and millisecond pulsars (MSPs), we use the latest Fermi Large Area Telescope catalog (4FGL-DR4) to investigate the implications of proposed γ-ray luminosity models. Using Monte Carlo techniques, we calculate the number of CPs and MSPs that would comprise the sample of pulsar-like unidentified sources (PLUIDs) in 4FGL-DR4. While radio beaming fractions were used to scale the sizes of the populations, when forming the mock 4FGL-DR4 samples we make the simplifying assumption that all γ-ray pulsars are beaming toward the Earth. We then explore the observable outcomes of seven different γ-ray luminosity models. Four of the models provide a good match to the observed number of PLUIDs, while three others significantly overpredict the number of PLUIDs. For these latter models, either the average beaming fraction of γ-ray pulsars is more like 25%–50%, or a revision in the luminosity scaling is required. Most of the radio-detectable MSPs that our models predict as part of the PLUIDs within 4FGL-DR4 are, unsurprisingly, fainter than the currently observed sample and at larger dispersion measures. For CPs, in spite of an excellent match to the observed radio population, none of the γ-ray models we investigated could replicate the observed sample of 150 γ-ray CPs. Further work is required to understand this discrepancy. For both MSPs and CPs, we provide encouraging forecasts for targeted radio searches of PLUIDs from 4FGL-DR4 to elucidate the issues raised in this study.

The LMC’s stellar bar is offset from the outer disk center, tilted from the disk plane, and does not drive gas inflows. These properties are atypical of bars in gas-rich galaxies, yet the LMC bar’s strength and radius are similar to typical barred galaxies. Using N-body hydrodynamic simulations, we show that the LMC’s unusual bar is explainable if there was a recent collision (impact parameter ≈2 kpc) between the LMC and SMC. Pre-collision, the simulated bar is centered and coplanar. Post-collision, the simulated bar is offset (≈1.5 kpc) and tilted (≈86). The simulated bar offset reduces with time, and comparing with the observed offset (≈0.8 kpc) suggests the timing of the true collision to be 150–200 Myr ago. Then, 150 Myr post-collision, the LMC’s bar is centered with its dark matter (DM) halo, whereas the outer disk center is separated from the DM center by ≈1 kpc. The SMC collision produces a tilted-ring structure for the simulated LMC, consistent with observations. Post-collision, the simulated LMC bar’s pattern speed decreases by a factor of 2. We also provide a generalizable framework to quantitatively compare the LMC’s central gas distribution in different LMC–SMC interaction scenarios. We demonstrate that the SMC’s torques on the LMC’s bar during the collision are sufficient to explain the observed bar tilt, provided the SMC’s total mass within 2 kpc was (0.8–2.4) × 10⁹M_⊙. Therefore, the LMC bar’s tilt constrains the SMC’s pre-collision DM profile, and requires the SMC to be a DM-dominated galaxy.

Totally eclipsing contact binaries provide a unique opportunity to accurately determine mass ratios through photometric methods alone, eliminating the need for spectroscopic data. Studying low mass ratio (LMR) contact binaries is crucial for advancing our understanding of binary star evolution and the formation of rare optical transients known as red novae. We identified 143 totally eclipsing contact binaries from the Transiting Exoplanet Survey Satellite. These high-precision light curves reveal a distinct O’Connell effect, which we interpret by introducing a cool spot on the primary star. Training a neural network model that includes cool spot parameters can generate a high-precision light curve 2 orders of magnitude faster than Phoebe. Utilizing the neural network (NN_nol3) model combined with the Markov Chain Monte Carlo algorithm, we rapidly derived the fundamental parameters of these systems. By leveraging the relationship between orbital period and semimajor axis using the Random Sample Consensus algorithm, we estimated their absolute parameters. Our analysis identified 96 targets with mass ratios below 0.25, all of which were not listed in any previous catalog, thus signifying the discovery of new LMR system candidates. Assuming all 143 binary systems are affected by a third light during parameter estimation, we train a neural network (NN_l3) model considering the third light. Then we calculate the residuals between the mass ratio q_l3 (considering the third light) and q_nol3 (neglecting it). For these residuals, the 25th percentile (Q₁) is 0.012, the median (Q₂) is 0.026, and the 75th percentile (Q₃) is 0.05.

In this paper, we conducted a linear instability analysis to investigate penetrative convection in rotating, tilted f-planes with multiple convectively stable and unstable layers. Our findings indicate that penetrative distance decreases with increasing rotational and stratification strengths. We also observed that teleconvection, multiroll convection, and cutoff convection, previously identified in two-layer models, are present in multilayer models. For a three-layer model, the flow exhibits an up-down symmetric pattern for penetrative convection at the poles. However, this symmetry is disrupted in tilted f-planes when the flow drifts in equatorward or poleward directions. At mid- to low latitudes, poleward flow tends to enhance penetration in the upper layers, while equatorward flow facilitates penetration in the lower layers. The disruption of up-down symmetry is also observed in multilayer models with more layers when oscillatory convection occurs. Our findings suggest that upward and downward penetration could be significantly different in stars or planets with multilayer structures. However, under a strong stable composition gradient, the instability is found to be reduced.

A fraction of the dense cores within a turbulent molecular cloud will eventually collapse to form stars. Identifying the physical criteria for instability and analyzing critical core properties is therefore necessary to star formation theory. Here we quantify the characteristics of an ensemble of “critical cores” on the verge of collapse. This critical epoch was identified in a companion paper, which followed the dynamical evolution of prestellar cores in numerical simulations of turbulent, self-gravitating clouds. We find that radial profiles of density and turbulent velocity dispersion in individual critical cores are consistent with our new model for turbulent equilibrium spheres. While a global linewidth–size relation exists for a cloud with given size and Mach number, the turbulent scaling relations around each core exhibit significant variations. As a result, there is no single density threshold for collapse; instead, cores collapse at a range of densities determined by the local sonic scale and gravitational potential environment. The critical cores in our simulations are mostly transonic; we do not find either purely thermal or highly turbulent cores. In our low Mach number model, which better resolves the characteristic mass and sonic scales, we find marginal evidence that the core mass function (CMF) of critical cores peaks around a characteristic mass scale associated with the large-scale cloud properties. We highlight the importance of constructing the CMF at the critical time for the purpose of testing gravoturbulent fragmentation theories, and derive the resolution requirements to unambiguously identify the peak of the CMF.

An analysis of the photometric growth and decay rates of sunspots and pores was carried out. According to the Solar Dynamics Observatory/Helioseismic and Magnetic Imager data for the period 2010 May–2025 March, ≈3.5 × 10⁵ sunspots and pores were detected and their evolution tracked. The growth and decay rates of sunspots depend nonmonotonically on the area. For small-area sunspots S ≲ 50 μsh, a rapid increase in velocity is observed with increasing area for the growth stage and for the decay stage μsh day⁻¹. For sunspots S ≳ 50 μsh, the growth rate depends weakly on the area: μsh day⁻¹. For the decay stage of sunspots with an area of S ≈ 50–150 μsh, the decay rate also depends weakly on the area and can be approximated as . For sunspot areas S ≳ 150 μsh, the decay rate accelerates with increasing area: μsh day⁻¹. For solar pores, the growth and decay rates of solar pores are linearly related to the area. The growth and decay rates for the spots of the leading and trailing polarities are determined. In the range of spot areas S ≈ 100–200 μsh, the growth and decay rates of sunspots of trailing polarity are higher than those of sunspots of leading polarity.

Neutral hydrogen serves as a crucial probe for the Cosmic Dawn and the Epoch of Reionization (EoR). Actual observations of the 21 cm signal often encounter challenges such as thermal noise and various systematic effects. To overcome these challenges, we simulate SKA-Low-depth images in the South Celestial Pole field and process them with a deep learning method. We utilized foreground residuals acquired by LOFAR during actual North Celestial Pole field observations, thermal and excess variances calculated via Gaussian process regression, and 21 cm signals generated with 21cmFAST for signal extraction tests. Our approach to overcome these foreground, thermal noise, and excess variance components employs a 3D U-Net neural network architecture for image analysis. When considering thermal noise corresponding to 1752 hr of integration time, U-Net provides reliable 2D power spectrum predictions, and robustness tests ensure that we get realistic EoR signals. Adding foreground residuals, however, causes inconsistencies below the horizon delay line. Lastly, evaluating both thermal noise and excess variances with observations up to 4380 hr and 13,140 hr ensures reliable power spectrum estimations within the EoR window and across nearly all scales, respectively. The incoherence of excess variances in the frequency direction can greatly affect deep learning to extract 21 cm signals.

CY Ari and IK Lyn are two eclipsing binary systems that share the same spectral type but exhibit significantly different metallicities. Based on the Wilson–Devinney (W-D) method, the first photometric solutions are obtained by analyzing the new complete BVR_cI_c light curves. The completely eclipsing nature of the light curves allows for the determination of reliable photometric parameters for both systems. Analysis of the light curves indicates that the two systems are structurally similar. Both belong to W-type shallow contact binary systems, with nearly identical degrees of contact. The O − C analysis demonstrates that the orbital periods of CY Ari and IK Lyn are increasing over the long term, with the increase rate for IK Lyn being significantly higher than that for CY Ari. This discrepancy may arise from different mass transfer rates from the secondary star to the primary star. Additionally, a periodic oscillation with a period of 5.4 yr has been detected in CY Ari, potentially attributable to the light-time effect of an unseen third body. An analysis of the age and evolutionary stage elucidates the reasons behind the divergent evolutionary paths of CY Ari and IK Lyn. The presence of the third body accelerates the evolution of CY Ari by removing angular momentum from the central binary pair. Although CY Ari was formed later than IK Lyn, it has evolved into a similar stage. This study provides critical evidence of the significant role played by a third body in the formation and evolution of contact binary systems.

We investigate UV continuum slopes β of 863 galaxies at 4 < z < 14 using archival JWST/NIRSpec PRISM spectra obtained from major JWST Guaranteed Time Observations (GTO), Early Release Science (ERS), and General Observers (GO) programs, including JADES, CEERS, and UNCOVER. Among these galaxies, we identify a remarkable galaxy at z = 9.25, dubbed extremely blue galaxy 1 (EBG-1), with a significantly blue UV slope β = −2.99 ± 0.15, unlike the rest of the galaxies that exhibit red continua or ambiguous blue continua hindered by large uncertainties. We confirm that the β value negligibly changes by the data reduction and fitting wavelength ranges for UV emission/absorption line masking. The extreme blue slope, β = −3.0, rules out significant contributions from dust extinction or AGN activity. Comparing with stellar and nebular emission models, we find that such a blue UV slope cannot be reproduced solely by stellar models even with very young, metal-poor, or top-heavy contiguous star formation associated with strong nebular continua making the UV slopes red, but with a high ionizing photon escape fraction, , for a weak nebular continuum. While the Hβ emission line is not detected, likely due to the limited sensitivity of the spectrum, we find moderately weak [O iii]λλ4959,5007 emission lines for the given star formation rate (3 M_⊙ yr⁻¹) and stellar mass (10^8.0M_⊙) that are about 3 times weaker than the average emission lines, again suggestive of the high ionizing photon escape fraction, or more. EBG-1 would provide crucial insights into stellar and nebular continuum emission in high-redshift galaxies, serving as an example of the ionizing photon escaping site at the epoch of reionization.

IGR J17014-4306 is the longest orbital period (12.8 hr) deep-eclipsing intermediate polar known, where a massive white dwarf (WD) accretes matter from its companion star via an accretion disk. Based on photometric observations from the Transiting Exoplanet Survey Satellite space telescope and the American Association of Variable Star Observers database, 70 eclipse timings were determined. It was also confirmed that the spin pulse profile of the WD does change, which is due to the amplitude variation with opposite trends in spin frequency and its first harmonic. This may be related to fluctuations in the accretion rate. The spin period shows slight fluctuations but no significant changing trends. We constructed the O–C diagram and discovered that the orbital period is increasing at a high rate of , which is comparable to those detected in compact binary supersoft X-ray sources and recurrent novae. This continuous increase in the orbital period is caused by the mass transfer from the less-massive companion to the WD on its thermal timescale at a high rate. All these findings suggest that IGR J17014-4306 is an interesting target to investigate nova eruption, the real angular momentum loss mechanism, and the overall evolution of cataclysmic variables.

Due to dust grain alignment with magnetic fields, dust polarization observations of far-infrared emission from cold molecular clouds are often used to trace magnetic fields, allowing a probe of the effects of magnetic fields on the star formation process. We present inferred magnetic field maps of the Pillars of Creation region within the larger M16 emission nebula, derived from dust polarization data in the 89 and 154 μm continuum using the Stratospheric Observatory For Infrared Astronomy/High-resolution Airborne Wideband Camera. We derive magnetic field strength estimates using the Davis–Chandrasekhar–Fermi method. We compare the polarization and magnetic field strengths to column densities and dust continuum intensities across the region to build a coherent picture of the relationship between star-forming activity and magnetic fields in the region. The projected magnetic field strengths derived are in the range of ∼50–130 μG, which is typical for clouds of similar n(H₂), i.e., molecular hydrogen volume density on the order of 10⁴–10⁵ cm⁻³. We conclude that star formation occurs in the finger tips when the magnetic fields are too weak to prevent radial collapse due to gravity but strong enough to oppose OB stellar radiation pressure, while in the base of the fingers the magnetic fields hinder mass accretion and consequently star formation. We also support an initial weak-field model (<50 μG) with subsequent strengthening through realignment and compression, resulting in a dynamically important magnetic field.

We conduct a systematic survey of X-ray sources in the inner (r ∼ 200 kpc) region of the Antlia cluster based on Chandra observations, down to a source detection limit of L(0.5–8 keV) ∼ 4.2 × 10⁻⁷ ph cm⁻² s⁻¹ (2 × 10³⁸ erg s⁻¹). We present an X-ray source catalog with 202 sources and provide their coordinates, multiband flux information, and hardness ratios. We find a statistically significant excess at a significance level of 4.2σ with 37.6 excess sources beyond 3 times the mean effective radius of the two brightest central galaxies (BCGs). This implies that these excess sources could be a genuine intracluster X-ray population that is not associated with the bulk stellar component. Also, the increased number of excess sources in the fields containing a BCG implies a potential connection between the excess sources and BCGs. The discovery of these sources in the Antlia cluster, together with previous research of similar findings in the other two nearby clusters, Virgo and Fornax, indicates that the intracluster X-ray population could be universal in nearby galaxy clusters. Furthermore, we discuss the candidate origins of the excess sources, including low-mass X-ray binaries (LMXBs) associated with intracluster light (ICL-LMXBs), LMXBs in globular clusters (GC-LMXBs), and supernova-kicked LMXBs (SN-kicked LMXBs). We estimate that the contribution of ICL-LMXBs, which should include the LMXBs related to the stellar halo surrounding BCGs, is unlikely to dominate the intracluster X-ray population in Antlia. Meanwhile, GC-LMXBs and SN-kicked LMXBs, each component could contribute ∼30% to the total excess sources.

Supermassive black holes (SMBHs) with dynamically measured masses have shown empirical correlations with host galaxy properties. These correlations are often the only method available to estimate SMBH masses and gather statistics for large galaxy populations across a range of redshifts, even though the scaling relations themselves are derived from a small subset of nearby galaxies. Depending on the scaling relation used, estimated SMBH masses can vary significantly. The most widely used scaling relations are the M_BH–M_bulge and M_BH–σ relations, where M_bulge is galaxy bulge mass and σ is the bulge velocity dispersion. In this paper, we determine how severely the choice of scaling relation impacts SMBH mass estimates for different subsets of a large galaxy population. For this analysis, we use a sample of ∼400,000 galaxies, including 1240 Type 1 active galactic nuclei from the Sloan Digital Sky Survey. We calculate SMBH masses from M_BH–M_bulge and M_BH–σ and compare to single-epoch virial SMBH masses from broad-line Hβ, which are derived independently of black hole–host galaxy scaling relations. We find that SMBH masses derived from the single-epoch virial relation for Hβ are better reproduced by M_BH–σ than M_BH–M_bulge. Finally, in cases where σ and M_bulge cannot be measured directly, we show that it is possible to infer σ from photometry with more accuracy than we can infer M_bulge.

We present a new technique for measuring the integrated galaxy light (IGL) with stacked image data from the Dark Energy Survey (DES). We extract 1′ × 1′ cutouts from nearly 100,000 randomly selected positions in the g, r, i, z, and Y bands from the DES Data Release 2 maps. We generate source catalogs and masks for each cutout, and the images are subsequently stacked to generate deep images of the sky both with and without sources. The IGL is then calculated by taking the difference in average brightness between stacks that contain galaxies and stacks in which galaxies have been masked. We find IGL values of g = 4.27 ± 0.28, r = 6.97 ± 0.42, i = 8.66 ± 0.53, z = 10.16 ± 0.7, and Y = 13.78 ± 2.35 nW m⁻² sr⁻¹. These measurements, which require no foreground estimation or removal, are in agreement with previously reported IGL values derived from galaxy number counts and other methods. This stacking technique reduces the sensitivity to diffuse local backgrounds but is not sensitive to large-scale diffuse extragalactic background light.

We report on Green Bank Telescope observations of the radio magnetar Swift J1818.0–1607 between 820 MHz and 35 GHz, taken from 6 to 9 months after its 2020 March outburst. We obtained multihour observations at six frequencies, recording polarimetric, spectral, and single-pulse information. The spectrum peaks at a frequency of 5.4 ± 0.6 GHz, making Swift J1818.0–1607 one of many radio magnetars that exhibit a gigahertz-peaked spectrum. The radio flux decays steeply above the peak frequency, with in-band spectral indices α < −2.3 above 9 GHz. The emission is highly (>50%) linearly polarized, with a lower degree (<30%) of circular polarization that can change handedness between single pulses. Across the frequency range of our observations, the time-integrated radio profiles share a common shape: a narrow “pulsar-like” central component flanked by “magnetar-like” components comprised of bright, spiky subpulses. The outer profile components exhibit larger degrees of flux modulation when compared to the central pulse component.

Long-term observations of the Galactic center by Fermi and HESS have revealed a novel phenomenon: the high-energy gamma-ray spectrum from the gamma-ray source HESS J1745-290 exhibits a double power-law structure. In this study, we propose a new explanation for this phenomenon. We suggest that the low-energy (GeV) power-law spectrum originates from interactions between trapped background “sea” cosmic ray particles and the dense gaseous environment near the Galactic center. In contrast, the bubble-like structure in the high-energy (TeV) spectrum is produced by protons accelerated during active phases of the Galactic center, through the same physical process. Based on this framework, we first calculate the gamma-ray emission generated by cosmic ray protons accelerated in the Galactic center. Then, using a spatially dependent cosmic ray propagation model, we compute the energy spectrum of background “sea” cosmic ray protons and their associated diffuse gamma-ray emission in the Galactic center region. The results closely reproduce the observations from Fermi-LAT and HESS, suggesting that their long-term data support this picture: high-energy cosmic rays in the local region originate from nearby cosmic ray sources, while low-energy cosmic rays are a unified contribution from distant cosmic ray sources. We anticipate that this double power-law structure may be widely present in the halo of a Galactic cosmic-ray source or a slow-diffusion region. We hope that future observations will detect more such sources, allowing us to further test and validate our model.

From the survival of dust disks for a few Myr to the establishment of chemical dichotomy, dust traps are expected to play a pivotal role in sculpting protoplanetary disks and the early planet formation process. These traps may not be perfect, as evidenced by both numerical simulations and the observations of disks with gaps and cavities, inside which we detect some amounts of both gas and dust. Using two-fluid hydrodynamic global simulations in both 2D and 3D, we directly compute the dynamics of dust grains as they aerodynamically interact with the disk gas that is being perturbed by an embedded planet. In both 2D and 3D, we find the dust trap to be more leaky for a lower-mass planet and for a more turbulent disk. More crucially, we find that the fraction of dust mass that remains trapped within the pressure bump can be up to an order of magnitude more reduced in 3D compared to 2D, with all else being equal. Our simulations show a complex behavior of dust radial motion that is both azimuthally and poloidally nonuniform, with the overall dynamics dominated by the dust coupling to the gas flow even for Stokes number 0.1. The leaky traps we find suggest that the pebble isolation mass is likely not truly isolating and that gap-opening planets do not establish an unconditional impermeable barrier. Our findings have implications for recent JWST MINDS results, which show that volatiles, including water, are present in the inner regions of disks hosting outer dust rings.

High-mass star formation involves complex processes, with the hot core phase playing a crucial role in chemical enrichment and the formation of complex organic molecules. However, molecular inventories in hot cores remain limited. Using data from the Atacama Large Millimeter/submillimeter Array Three-millimeter Observations of Massive Star-forming regions survey, the molecular composition and evolutionary stages of two distinct millimeter continuum sources in the high-mass star-forming region G336.99-00.03 have been characterized. MM1, with 19 distinct molecular species detected, along with eight isotopologues and several vibrationally/torsionally excited states, has been identified as a hot core. MM2, with only five species identified, was defined as a H ii region. Isotopic ratios in MM1 were derived, with ¹²C/¹³C ranging from 16.0 to 29.2, ¹⁶O/¹⁸O at 47.7, and ³²S/³⁴S at 19.2. Molecular abundances in MM1 show strong agreement with other sources and three-phase warm-up chemical models within an order of magnitude for most species. Formation pathways of key molecules were explored, revealing chemical links and reaction networks. This study provides a detailed molecular inventory of two millimeter continuum sources, shedding light on the chemical diversity and evolutionary processes in high-mass star-forming regions. The derived molecular parameters and isotopic ratios offer benchmarks for astrochemical models, paving the way for further investigation into the formation and evolution of complex organic molecules during the hot core phase.

The C-19 star stream has the abundance characteristics of an unusually metal-poor globular cluster but kinematically is uncharacteristically hot and wide for a cluster stream, having a line-of-sight velocity dispersion of 7  ±  2 km s⁻¹ and a 1σ width of 240 pc. We show that the tidal dissolution of an old, lower-mass globular cluster in a cold dark matter (CDM) galactic halo can create a hot, wide stream currently near orbital apocenter. A cosmological Milky Way n-body simulation motivates the parameters for an evolving Milky Way halo potential containing an orbiting subhalo population in which we model a star cluster progenitor of C-19. The same model parameters have been used for a GD-1 stream model. The ∼7 km s⁻¹ velocity dispersion is readily accomplished with an evolving CDM subhalo population, a progenitor cluster mass ≃2 × 10⁴M_⊙, and an orbit that keeps the progenitor orbital pericenter within about 10 kpc of the Milky Way dark halo or its precursors.

The J-region asymptotic giant branch (JAGB) is an overdensity of stars in the near-infrared, attributed to carbon-rich AGB stars, and recently used as a standard candle for measuring extragalactic distances and the Hubble constant. Using JWST in Cycle 2, we extend JAGB measurements to six hosts of nine Type Ia supernovae (SNe Ia; NGC 2525, NGC 3147, NGC 3370, NGC 3447, NGC 5468, and NGC 5861), with two at D ∼ 40 Mpc, all calibrated by the maser host NGC 4258. We investigate the effects of incompleteness and are unable to recover a JAGB measurement for NGC 3147. We compile all JWST JAGB observations of SN Ia hosts, 15 galaxies hosting 18 SNe Ia, from the SH0ES and CCHP programs, and employ all literature measures. We find no significant mean difference between these distances and those from Hubble Space Telescope Cepheids, −0.03 ± 0.02 (stat.) ± 0.05 (sys.) mag. We find a difference of 0.11 ± 0.022 mag between JAGB mode measurements in the CCHP analyses of two fields in NGC 4258, a feature also seen in two SH0ES fields (see field-to-field variations in S. Li et al.), indicating significant variation of NGC 4258 JAGB measurements, which produce a large absolute calibration uncertainty. Variations are also seen in the shape of the JAGB luminosity function (LF) across galaxies so that different measures produce different values of the Hubble constant. We look for but do not (yet) find a standardizing relation between JAGB LF skew or color dependence and the apparent variation. Using the middle result of all JAGB measures to calibrate SNe Ia yields a Hubble constant of H₀ = 73.3 ± 1.4 (stat.) ± 2.0 (sys.) km s⁻¹ Mpc⁻¹ with the systematic dominated by apparent differences across the NGC 4258 calibrating fields or their measures.

We generalize a magnetogram-matching Biot–Savart law (BSl) from planar to spherical geometry. For a given coronal current density J, this law determines the magnetic field whose radial component vanishes at the surface. The superposition of with a potential field defined by a given surface radial field, B_r, provides the entire configuration where B_r remains unchanged by the currents. Using this approach, we (1) upgrade our regularized BSls for constructing coronal magnetic flux ropes (MFRs) and (2) propose a new method for decomposing a measured photospheric magnetic field as , where the potential, B_pot, toroidal, B_T, and poloidal, , fields are determined by B_r, J_r, and the surface divergence of B–B_pot, respectively, all derived from magnetic data. Our B_T is identical to the one in the alternative Gaussian decomposition by P. W. Schuck et al., while B_pot and are different from their poloidal fields and , which are potential in the infinitesimal proximity to the upper and lower side of the surface, respectively. In contrast, our has no such constraints and, as B_pot and B_T, refers to the same upper side of the surface. In spite of these differences, for a continuous J distribution across the surface, B_pot and are linear combinations of and . We demonstrate that, similar to the Gaussian method, our decomposition allows one to identify the footprints and projected surface-location of MFRs in the solar corona, as well as the direction and connectivity of their currents.

We present the detection of a previously unknown giant molecular cloud (GMC) located at the midpoint of the Galactic Bar Dust Lanes (M4.7–0.8), using spectral line observations taken with the Green Bank Telescope. This  ∼60 pc long GMC is associated with accreting material that is transitioning from the quieter Galactic disk environment to the more extreme central molecular zone (CMZ) environment. Our 24 GHz single-dish radio observations targeted the NH₃ (1,1)−(4,4) and HC₅N (9−8), known dense gas tracers. The observations reveal the main features of the GMC, which we have dubbed the “Nexus” and “Filament,” covering a 05 × 025 area at 31″ angular resolution. In this publication, we investigate the gas kinematics within the observed region and compare the distribution of molecular emission to previous infrared surveys to better understand the dust component. The observed gas tracers show centrally condensed cores corresponding to the positions of high dust column densities and low dust temperatures. We report the detection of a previously unknown NH₃ (3,3) maser, along with a 70 μm source association, which supports the identification of this region as being actively star-forming. Gas emission in this region shows broad linewidths, comparable to values seen in CMZ clouds. The overall description of this cloud that we present is that of a highly dynamic region comprising dense gas and dust. This encapsulates a wide range of features associated with star formation, in addition to material transport related to the CMZ.

The solar corona is much hotter than lower layers of the solar atmosphere—the photosphere and chromosphere. The coronal temperature is up to 1 MK in quiet Sun areas, while up to several megakelvins in active regions, which implies a key role of the magnetic field in coronal heating. This means that understanding coronal heating requires reliable modeling of the underlying 3D magnetic structure of an active region validated by observations. Here, we employ synergy between 3D modeling, optically thick gyroresonant microwave emission, and optically thin EUV emission to (i) obtain and validate the best magnetothermal model of the active region and (ii) disentangle various components of the EUV emission known as diffuse component, bright loops, open-field regions, and “moss” component produced at the transition region. Surprisingly, the best thermal model corresponds to high-frequency energy release episodes, similar to a steady-state heating. Our analysis did not reveal significant deviations of the elemental abundances from the standard coronal values.

Studies from recent years have reached different conclusions regarding how frequently super-Earths are accompanied by long-period giant planets and vice versa. This relation has been predicted to be mass dependent by planet-formation models. We investigate that as the origin of the discrepancy using a radial velocity sample: the California Legacy Survey. We perform detection completeness corrections in order to discard detection bias as a possible explanation to our results. After bias corrections, we find that cold Jupiters are times more massive when not in the company of an inner super-Earth, while super-Earths are not significantly more massive while in the company of an outer giant planet. We also report an occurrence enhancement for Saturns (median projected mass of 0.6M_J) while in presence of a super-Earth by a factor of ∼4, and for super-Earths in the presence of Saturns by the same factor. This positive correlation disappears for super-Jupiters (median projected mass of 3.1M_J). These results show that while cold Jupiters are generally accompanied by inner super-Earths, this does not hold for the largest giant planets, such as those that will be discovered by Gaia, which will likely not be accompanied by transiting planets. The mass dependence, in combination with the different detection limits of different surveys, may explain the discrepancies concerning occurrence relations between cold Jupiters and super-Earths.

The relationship between magnetic activity and Rossby number is one way through which stellar dynamos can be understood. Using measured rotation rates and X-ray to bolometric luminosity ratios of an ensemble of stars, we derive empirical convective turnover times based on recent observations and reevaluate the X-ray activity–Rossby number relationship. In doing so, we find a sharp rise in the convective turnover time for stars in the mass range of 0.35−0.4 M_⊙, associated with the onset of a fully convective internal stellar structure. Using MESA stellar evolution models, we infer the location of dynamo action implied by the empirical convective turnover time. The empirical convective turnover time is found to be indicative of dynamo action deep within the convective envelope in stars with masses 0.1–1.2 M_⊙, crossing the fully convective boundary. Our results corroborate past works suggesting that partially and fully convective stars follow the same activity–Rossby relation, possibly owing to similar dynamo mechanisms. Our stellar models also give insight into the dynamo mechanism. We find that empirically determined convective turnover times correlate with properties of the deep stellar interior. These findings are in agreement with global dynamo models that see a reservoir of magnetic flux accumulates deep in the convection zone before buoyantly rising to the surface.

We utilized Lyα radiative transfer calculations from H. Song et al. to investigate the properties of extended Lyα halos around star-forming galaxies in the Hubble Ultra Deep Field, observed by the Multi-Unit Spectroscopic Explorer. Expanding on the work of H. Song et al., which was limited to eight galaxies, we derived best-fit models for a significantly larger sample of 163 galaxies, which successfully reproduced both their Lyα spectra and surface brightness profiles (SBPs). These best-fit models suggest a broad medium distribution surrounding each galaxy, with low expanding velocities at large radii. This conclusion could not have been drawn from modeling either the spectrum or SBP alone, but only through simultaneous modeling of both. Our correlation analysis between observables and model parameters reveals that the spatial extent of Lyα halos is primarily determined by the extents of the medium and the source, while the spectral peak shift and full width at half maximum are governed mainly by optical depth, with the velocity structure of the medium playing a secondary yet nonnegligible role. The fact that various correlations derived from the full set of models and those from the best-fit subset can differ significantly highlights the complex and interdependent nature of Lyα radiative transfer. All model parameters interact to shape the observed Lyα features in a nontrivial way.

Axions are one of the leading dark matter candidates. If we are embedded in a Milky Way dark matter halo comprised of axions, their stimulated decay would enable us to observe a counterimage (“axion gegenschein”) with a frequency equal to half the axion mass in the opposite direction of a bright radio source. This spectral line emission will be broadened to Δν/ν ∼ σ_d/c ∼ 10⁻³ due to the velocity dispersion of dark matter, σ_d. In this pilot study, we perform the first search for the expected axion gegenschein image of Vela supernova remnant with 26.4 hr of effective ON–OFF data from the Five-hundred-meter Aperture Spherical radio Telescope (FAST) L-band (1.0–1.5 GHz) 19 beam receiver. Our null detection limits the axion–photon coupling strength to be g_aγγ ≲ 2 × 10⁻¹⁰ GeV⁻¹ in the mass ranges of 8.7 μeV ≤ m_a ≤ 9.44 μeV and 10.85 μeV ≤ m_a ≤ 12.01 μeV. These results provide a stronger constraint on g_aγγ in this axion mass range than the current limits obtained by the direct search of an axion decay signal from a dwarf galaxy that uses FAST observations, but are a factor of ∼3 times weaker than the current CERN Axion Solar Telescope limit. Based on our observation strategy, data processing methods, and results, the expected sensitivity will reach ∼10⁻¹¹ GeV⁻¹ with ∼2000 hr of observation in the future.

We present a systematic study of the recently reported anticorrelation between X-ray flux and photon index (Γ) in the Crab Nebula, using archival Rossi X-Ray Timing Explorer (RXTE) Proportional Counter Array (3–50 keV), RXTE High Energy X-ray Timing Experiment (HEXTE; 20–100 keV), and Nuclear Spectroscopic Telescope Array (3–78 keV) observations. Spectra were extracted in soft (3–10 keV) and hard bands (10–50, 10–78, 20–100 keV) and fitted with an absorbed power-law model. Across all instruments and energy ranges, we confirm the existence of a persistent negative correlation–harder spectra at higher flux levels. The correlation is stronger in the hard bands compared to the soft bands. This is consistent with synchrotron emission modulated by magnetic-field variations in the pulsar wind nebula.

Millimeter continuum spiral arms have so far only been detected in a handful of protoplanetary disks, and thus we have a limited understanding of the circumstances in which they can form. In particular, substructures in small disks (R ⪅ 50 au) have not been well characterized in comparison with large disks. We present Atacama Large Millimeter/submillimeter Array 1.3 mm continuum observations of the disk around the T Tauri star Haro 6-13 at a resolution of (∼5 au). A pair of low-contrast spiral arms are detected at disk radii from ∼10 to 35 au. They can be approximated as Archimedean spirals with pitch angles ranging from ∼10° to 30°. The low value of the disk-averaged spectral index between 1.3 and 3 mm (α = 2.1) and the high brightness temperatures suggest that the millimeter continuum is likely optically thick and thus may hide sufficient mass for the disk to become gravitationally unstable and form spiral arms. CO observations have shown that Haro 6-13 is surrounded by an envelope, raising the possibility that infall is facilitating spiral arm formation.

Jets and outflows are commonly observed in young stellar objects, yet their origins remain debated. Using 3D nonideal magnetohydrodynamic (MHD) simulations of a circumstellar disk threaded by a large-scale open poloidal magnetic field, we identify three components in the disk-driven outflow: (1) a fast, collimated jet, (2) a less collimated, slower laminar disk wind, and (3) a magneto-rotational instability (MRI)-active turbulent disk wind that separates the former two. At high altitudes, the MRI-active wind merges with the laminar disk wind, leaving only the jet and disk wind as distinct components. The jet is powered by a novel mechanism in the star formation context: a lightly mass-loaded outflow driven by toroidal magnetic pressure in the low-density polar funnel near the system’s rotation axis. A geometric analysis of the magnetic field structure confirms that magnetic tension does not contribute to the outflow acceleration, with magnetic pressure acting as the dominant driver. While the outflow in our model shares similarities with the magneto-centrifugal model—such as angular momentum extraction from the accreting disk—centrifugal forces play a negligible role in jet acceleration. In particular, the flow near the jet base does not satisfy the conditions for magneto-centrifugal wind launching. Additionally, the jet in our simulation exhibits strong spatial and temporal variability. These differences challenge the applicability of rotation–outflow velocity relations derived from steady-state, axisymmetric magneto-centrifugal jet models for estimating the jet’s launching radius. For the slower disk wind, vertical motion is driven by toroidal magnetic pressure, while centrifugal forces widen the wind’s opening angle.

In the week including Mother’s Day 2024, active region (AR) 13664 became superactive when AR 13668 emerged nearby, causing multiple X-class flares and coronal mass ejections, and an increase in activity level similar to that inferred from geomagnetic storms associated with the historic 1859 events. By analyzing both global warped toroids on which the active regions are strung, and active-region-scale magnetic flux and helicity, we find (i) the north and south toroids have nearly identical warped patterns, with mostly longitudinal wave numbers m = 1–3; (ii) in three longitude intervals the north and south toroids were tipped away from each other in latitude, with a longitude phase shift between them, creating locations most prone to AR eruptions; (iii) on an active region scale, vector magnetic fields deviate far from potential fields, and therefore contain large amounts of magnetic “free energy” available for conversion into kinetic energy and high-temperature radiation; (iv) the positive and negative polarities converge toward each other, facilitating reconnection and magnetic energy release; and (v) rapid changes in magnetic helicity, caused by helicity injection from below that creates helicity imbalances. Despite the coarser resolution of GONG magnetograms, the derived global toroids are strikingly similar to those derived from the Solar Dynamics Observatory's Helioseismic and Magnetic Imager. We conclude that the Mother’s Day superstorms were caused by enhanced magnetic complexity occurring due to intricate interactions among multiple active regions emerging at nearly the same locations. This suggests that predicting the locations of magnetically complex active regions, and studying and tracking their eruptive states using different proxy parameters can greatly improve our ability to forecast intense storms, not only hours but potentially weeks in advance.

This work presents comprehensive multifrequency radio monitoring of the black hole low-mass X-ray binary (LMXB) Swift J1727.8−1613, which underwent its first recorded outburst after its discovery in 2023 August. Through a considerable community effort, we have coalesced the data from multiple, distinct observing programs; the light curves include ∼10 months and 197 epochs of monitoring from seven radio facilities with observing frequencies ranging from (approximately) 0.3–230 GHz. The primary purpose of this work is to provide the broader astronomical community with these light curves to assist with the interpretation of other observing campaigns, particularly nonradio observing frequencies. We discuss the phenomenological evolution of the source, which included (i) multiple radio flares consistent with the launching of discrete jet ejections, the brightest of which reached ∼1 Jy; (ii) temporally evolving radio spectral indices (α), reaching values steeper than expected for optically thin synchrotron emission (α < −1) and emission with significant radiative cooling (α < −1.5). We have published a digital copy of the data and intend for this work to set a precedent for the community to continue releasing comprehensive radio light curves of future LMXB outbursts.

Observations with the James Webb Space Telescope (JWST) have identified an abundant population of supermassive black holes (SMBHs) already in place during the first few hundred million years of cosmic history. Most of them appear overmassive relative to the stellar mass in their host systems, challenging models of early black hole seeding and growth. Multiple pathways exist to explain their formation, including heavy seeds formed from direct collapse/supermassive stars or sustained super-Eddington accretion onto light stellar remnant seeds. We use the semianalytical code Ancient Stars and Local Observables by Tracing Halos to predict the emerging SMBH mass function under physically motivated models for both light- and heavy-seed formation, to be compared with upcoming ultradeep JWST surveys. We find that both pathways can reproduce observations at z ∼ 5–6, but have distinct features at higher redshifts of z ∼ 10. Specifically, JWST observations have the potential to constrain the fraction of efficiently accreting (super-Eddington) SMBHs, as well as the existence and prevalence of heavy seeds, in particular through ultradeep observations of blank fields and/or gravitational lensing surveys. Such observations will provide key insights to understand the process of SMBH formation and evolution during the emergence of the first galaxies. We further emphasize the great promise of possible SMBH detections at z ≳ 15 with future JWST observations to break the degeneracy between light- and heavy-seed models.

We present the first detection of spatially resolved protostellar outflows and jets in the outer Galaxy. We observed five star-forming regions in the outer Galaxy (Sh 2-283 and NOMF05-16/19/23/63; galactocentric distance = 15.7–17.4 kpc) with the Atacama Large Millimeter/submillimeter Array. Toward Sh 2-283, we have detected distinct outflow (∼5–50 km s⁻¹) and jet components (∼50–100 km s⁻¹) associated with the protostar in CO(3–2) emission. The outflows and jets are well collimated, with the jets exhibiting multiple bullet structures. The position–velocity diagram along the CO flow axis shows two characteristic structures: (a) the flow velocity, which linearly increases with the position offset from the core center (the Hubble-like flow); and (b) the continuous velocity components of the periodical flows (spine-like structures), which may indicate episodic mass ejection events. The time intervals of the mass ejection events are estimated to be 900–4000 yr, based on the slopes of these spine-like structures. These characteristics align with those of nearby protostellar systems, indicating that early star formation in low-metallicity environments, such as the outer Galaxy, resembles that in the inner Galaxy. In contrast to the physical similarities, the N(SiO)/N(CO) ratio in the jet bullet appears to be lower than that measured in the low-mass protostellar sources in the inner Galaxy. This may indicate a different shock chemistry or different dust composition in the outer Galaxy source, although non–local thermodynamic equilibrium effects could also affect the observed low N(SiO)/N(CO) ratio. We also report the new detection of four other outflow sources in the outer Galaxy.

V1674 Her is one of the fastest novae, of which the very early phase is well observed, including optical rise to the peak over 10 mag. We present a full theoretical light-curve model of V1674 Her. Our 1.35 M_⊙ white dwarf (WD) model with the mass accretion rate of 1 × 10⁻¹¹M_⊙ yr⁻¹ explains overall properties including a very fast rise and decay of the optical V light curve. The WD photosphere expands up to 21 R_⊙, thus a 0.26 M_⊙ companion star orbiting the WD every 3.67 hr is engulfed 2.7 hr after the onset of thermonuclear runaway and appears 5.3 days after that. The duration of X-ray flash is only 0.96 hr. The evolution of the expanding envelope and temporal change of the photospheric radius are very consistent with observed optical and X-ray modulations with the orbital and spin (501 s) periods. We confirm that the decay phase of the nova light curve is well approximated by a sequence of steady-state envelope solutions. Using the time-stretching method of nova light curves, we obtain the V-band distance modulus of (m − M)_V = 16.3 ± 0.2 and determine the distance to be d = 8.9 ± 1 kpc for the interstellar extinction of E(B – V) = 0.5 ± 0.05.

We present a study of the double-lined spectroscopic binary HD 21278 that contains one of the brightest main-sequence stars in the young α Persei open cluster. We analyzed new spectra and reanalyzed archived spectra to measure precise new radial velocity curves for the binary. We also obtained interferometric data using the CHARA Array at Mount Wilson to measure the sky positions of the two stars and the inclination of the ∼2 mas orbit. We determine that the two stars have masses of 5.381 ± 0.084 M_⊙ and 3.353 ± 0.064 M_⊙. From isochrone fits, we find the cluster’s age to be 49  ±  7 Myr (using PARSEC models) or 49.5 ± 6 Myr (MIST models). Finally, we revisit the massive white dwarfs that are candidate escapees from the α Persei cluster to try to better characterize the massive end of the white dwarf initial–final mass relation. The implied progenitor masses challenge the idea that Chandrasekhar-mass white dwarfs are made by single stars with masses near 8 M_⊙.

Physics-informed neural networks (PINNs) have emerged as a powerful tool for solving differential equations by integrating physical laws into the learning process. This work leverages PINNs to simulate gravitational collapse, a critical phenomenon in astrophysics and cosmology. We introduce the Schrödinger–Poisson (SP) informed neural network which solves the nonlinear SP equations to simulate the gravitational collapse of fuzzy dark matter (FDM) in both 1D and 3D settings. The results demonstrate accurate predictions of key metrics such as mass conservation, density profiles, and structure suppression, validating against known analytical or numerical benchmarks. This work highlights the potential of PINNs for efficient, possibly scalable modeling of FDM and other astrophysical systems, overcoming the challenges faced by traditional numerical solvers due to the nonlinearity of the involved equations and the necessity to resolve multiscale phenomena, especially resolving the fine wave features of FDM on cosmological scales.

We report the timing results with Insight-HXMT observations of X-ray binary IGR J19294+1816 during its 2019 type I outburst at the decline phase shortly following its peak. We analyze the light curves and power density spectrum of the 2019 observations and reveal a peak at ν_NS ∼ 80.2 mHz, corresponding to X-ray pulsations from the neutron star. In addition, a significant quasi-periodic oscillation (QPO) feature is observed at ν_QPO ∼ 30.2 mHz from 10 to 50 keV, with the rms amplitude increasing with energy. Furthermore, we detect two QPOs at frequencies of ∼51.1 and 113.7 mHz (corresponding to sidebands near ν_NS ± ν_QPO) in the range 25–50 keV, exhibiting an rms amplitude of around 12%. Wavelet analysis also shows multiple QPOs at the frequencies of ∼30 mHz, 50 and 110 mHz, which have transient behaviors. The centroid frequencies of ∼30 mHz remain nearly constant for different luminosities. Our research identifies IGR J19294+1816 as the second strong magnetic field pulsar with significant sideband signals around the spin frequency. We explore various physical origins that could explain the presence of multiple QPOs.

Identifying key observables is essential for enhancing our knowledge of exoplanet habitability and biospheres, as well as improving future mission capabilities. While currently challenging, future observatories such as the Large Interferometer for Exoplanets (LIFE) will enable atmospheric observations of a diverse sample of temperate terrestrial worlds. Using thermal emission spectra that represent conventional predictions of atmospheric CO₂ variability across the habitable zone (HZ), we assess the ability of the LIFE mission—as a specific concept for a future space-based interferometer—to detect CO₂ trends indicative of the carbonate–silicate (Cb–Si) weathering feedback, a well-known habitability marker and potential biological tracer. Therefore, we explore the feasibility of differentiating between CO₂ trends in biotic and abiotic planet populations. We create synthetic exoplanet populations based on geochemistry-climate predictions and perform retrievals on simulated thermal emission observations. The results demonstrate the robust detection of population-level CO₂ trends in both biotic and abiotic scenarios for population sizes as small as 30 exo-Earth candidates (EECs) and the lowest assessed spectrum quality in terms of signal-to-noise ratio, S/N = 10, and spectral resolution, R = 50. However, biased CO₂ partial pressure constraints hinder accurate differentiation between biotic and abiotic trends. If these biases were corrected, accurate differentiation could be achieved for populations with ≥100 EECs. We conclude that LIFE can effectively enable population-level characterization of temperate terrestrial atmospheres and detect CO₂ trends driven by the Cb–Si cycle as habitability indicators. Nevertheless, the identified biases underscore the importance of testing atmospheric characterization performance against the broad diversity expected for planetary populations.

The E_p,i–L_iso correlation of long gamma-ray bursts (LGRBs) is regarded as a fundamental correlation for standardizing LGRBs to probe cosmology and constrain LGRB physics. However, this correlation may be affected by potential selection effects, which are likely overlooked in the current small LGRB redshift sample. In this work, we simulate a large LGRB sample that reflects the observed situation, aiming to study the impact of peak flux P on the observed LGRB E_p,i–L_iso correlation. We find that the overall E_p,i and L_iso distribution, which will directly affect the best-fit result of the correlation, is significantly dependent on the value of P. This indicates that the impact of peak flux selection should be carefully considered in the studies and applications of the E_p,i–L_iso correlation. Notably, we show that our simulated data can reproduce the observed P distribution only if some dependence between E_p,i and L_iso is included in the simulation. This is an indication that the E_p,i–L_iso connection is a crucial property of LGRBs. We also find that GRBs with high peak flux in the low-E_p,i and L_iso region are not the straightforward extrapolation of the GRB population in the higher-E_p,i and L_iso region. Selecting four bursts with L_iso ≤ 10⁵⁰ erg s⁻¹, E_p,i ≤ 10^2.5 keV, and P ≥ 10^0.5 ph cm⁻² s⁻¹, we find two bursts, GRB 060614 and GRB 191019A, which may not be associated with the theoretical massive-star origin of LGRBs. This suggests that combining P with the position in the E_p,i–L_iso diagram may be used to indicate alternative LGRB origins.

Accurate forecasting of geomagnetic disturbances is essential for mitigating space weather effects on critical infrastructure. We present an optimized Long Short-term Memory neural network (LSTM+), refined through a reforecast procedure and hyperparameter tuning using data from Solar Cycle 24, achieving high predictive skill. For Solar Cycle 24, the model demonstrates a Nash–Sutcliffe efficiency of 0.95 for Ap and 0.78 for Dst, with Pearson correlation coefficients of 0.983 and 0.901, respectively. Furthermore, the error rate for predicting the peak Ap and trough Dst values was low, at 4.16% and 7.77%, respectively. This LSTM+ model is used to predict the Ap and Dst indices for Solar Cycle 25. The model forecasts a peak in Ap around 2026 January and a trough in Dst around 2026 February, consistent with the observed lag of up to 3 yr between geomagnetic indices and the sunspot number maximum in prior cycles. Validation against historical data confirms the model’s reliability in capturing these temporal offsets. These projections offer a predictive framework for improving space weather preparedness and safeguarding technological systems.

Collisionless magnetic reconnection is postulated to be active in many regions of the heliosphere, where the physics and formation of heliospheric structures are influenced by pickup ions (PUIs). Recent investigations suggest that the presence of PUIs may enhance the reconnection rate due to PUI-induced turbulence. Our investigation from particle-in-cell simulations with seed PUI shell velocity distributions reveals that the distributions remain quasi-stable within the reconnection exhaust region. The reconnection rate is rather suppressed as compared with non-PUI reconnection simulations. The PUI population eventually responds to the reconnection dynamics and forms a thicker current sheet layer. Both PUI and regular ion populations develop sub-ion-Alfvénic outflow jets, although PUI outflows are slower in comparison and extend beyond the separatrix surface. We predict that a future Interstellar Probe mission may encounter reconnecting current sheet layers in the outer heliosphere that demonstrate an initial slow modulation followed by a sharp rotation of the reconnecting magnetic field toward the center of the layer.

X-ray observations are essential for understanding the multimessenger emission mechanisms of active galactic nuclei (AGN). Blazars, a subset of AGN whose X-ray emission predominantly originates from relativistic jets, have been proposed as promising high-energy neutrino sources. In this work, we study the candidate neutrino-emitting blazar 5BZB J0630-2406, which has been observed over multiple epochs with the XMM-Newton, NuSTAR, Neil Gehrels Swift-XRT, and eROSITA observatories. Analysis of the X-ray spectra in the 2.0–10.0 keV band shows significant variability, with high-flux states adhering to a power-law model indicative of jet emission. However, during low-flux states, the spectrum reveals an additional component in hard X-rays, indicating a transition from jet-dominated to multicomponent X-ray emission, possibly associated with hadronic processes. To investigate this spectral evolution, we tested various models and found it to be consistent with coronal emission or photoionized absorption processes typically observed in obscured AGN. The identification of the X-ray spectral variability in 5BZB J0630-2406, combined with its potential for neutrino production, opens new perspectives in multimessenger astrophysics of blazars, highlighting the synergies between the mechanisms of the jet and the nuclear environment.

Upcoming surveys are likely to discover a new sample of interstellar objects (ISOs) within the solar system, but questions remain about the origin and distribution of this population within the Galaxy. ISOs are ejected from their host systems with a range of velocities, spreading out into tidal streams—analogous to the stellar streams routinely observed from the disruption of star clusters and dwarf galaxies. We create a simulation of ISO streams orbiting in the Galaxy, deriving a simple model for their density distribution over time. We then construct a population model to predict the properties of the streams in which the Sun is currently embedded. We find that the number of streams encountered by the Sun is quite large, ∼10⁶ or more. However, the wide range of stream properties means that for reasonable future samples of ISOs observed in the solar system, we may see ISOs from the same star (“siblings”), and we are likely to see ISOs from the same star cluster (“cousins”). We also find that ISOs are typically not traceable to their parent star, though this may be possible for ISO siblings. Any ISOs observed with a common origin will come from younger, dynamically colder streams.

Observations of the line-of-sight (LOS) component of emitter velocities in galaxies are valuable for reconstructing their two-dimensional (2D) velocity fields, albeit requiring certain assumptions. A common one is that radial flows can be neglected in the outer regions of galaxies, while their geometry can be deformed by a warp. A specular approach assumes that galactic disks are flat but allows for the presence of radial flows. This approach enables the reconstruction of 2D velocity maps that encompass both the transversal and radial velocity fields. Through the study of velocity fields in toy disk models, we find that the presence of warps is manifested as a dipolar correlation between the two velocity components obtained by assuming a flat disk. This shows that the analysis of angular velocity anisotropies provides an effective tool for breaking the degeneracy between warps and radial flows. We have applied these findings to the analysis of velocity fields of the galaxies from the THINGS sample and M33. Many of these galaxies exhibit such a dipolar correlation, indicating the presence of warps. However, we have found that the warp alone cannot explain all variations in the velocity field, suggesting that intrinsic perturbations are common. Furthermore, we have observed that the spatial distribution of the LOS velocity dispersion may correlate with both velocity components, providing independent evidence of nontrivial velocity fields. These findings offer a robust approach to reconstructing the velocity fields of galaxies, allowing us to distinguish between the presence of warps and complex velocity structures by assessing their relative amplitude.

We investigate the realization of quintom scenario for dynamical dark energy within modified gravity theories that can efficiently fit the recent observational data sets. Starting from a general effective field theory formulation of dark energy in metric-affine geometry, we derive the background action in unitary gauge and we demonstrate how both f(T) and f(Q) gravity can naturally realize quintom behavior through appropriate forms and parameter choices. Additionally, using the Gaussian process reconstruction of the latest Dark Energy Spectroscopic Instrument DR2 baryon acoustic oscillation data combined with Type Ia supernovae and cosmic microwave background observations, we extract the reconstructed dark-energy equation-of-state parameter, showing that it exhibits quintom-type evolution, crossing the phantom divide from below. Moreover, through detailed parameter estimations and application of information criteria, we compare the model with the quadratic one and the ΛCDM model. Our results show that, due to its rich structure, modified gravity stands as one of the main candidates for the realization of the data-favored dynamical dark energy.

Recent observations indicate that both the Milky Way bulge and inner halo exhibit angular momentum, although the origin and evolution of this prograde signature remain ambiguous. One plausible scenario involves secular evolution induced by the central bar and spiral arms. In this study, we identified a component consisting of 1,175,737 stars with net rotation through the application of a neural network (NN) method. To investigate the composition of this rotating sample and the origin of its rotation, we conducted a test particle simulation incorporating an equilibrium axisymmetric background potential together with a central decelerating bar. The test particles were generated using a distribution function model derived from observational constraints. Our results indicate that the decelerating bar transfers angular momentum to the pseudo-stars, and the rotational profile from our simulation shows strong agreement with observational data. These findings suggest that the rotating sample identified by our NN model is predominantly comprised of bulge, halo, and thick disk stars, and that the central decelerating bar is pivotal in shaping the inner Galaxy’s kinematics through angular momentum transfer.

This study focuses on stars with masses above the Kraft break in the Kepler field. Their rotational angular momenta are essentially the same as those at the zero-age main sequence. The angular momentum dissipation experienced by these stars during their pre-main sequence (PMS) phase is also relatively weak, so their rotational angular momentum can reflect the parameters of their parental molecular clouds. The reliability of angular momentum measurements was evaluated based on the phenomenon of angular momentum conservation observed in stars before and after the turnoff point in observational data. We find that stars with masses between 1.4M_⊙ and 1.8M_⊙ show an inverse proportionality between angular momentum and isochrone age. We propose that the angular momentum–age correlation reflects changes in the star-forming environment in the Milky Way’s history. Besides, the observed inverse proportionality implies that as the Milky Way has evolved, the stars formed within it tend to possess greater rotational angular momenta. This trend would promote the fragmentation of stars during the PMS phase and inhibit the formation of massive stars, providing a useful perspective for explaining variations in the initial mass function.

High spatial and spectral resolution observations are essential for identifying subarcsecond dual and lensed quasars and confirming their redshifts. We present Gemini/Gemini Multi-Object Spectrograph and Hubble Space Telescope/STIS optical spectra for 27 dual quasar candidates selected based on their variability-induced astrometric noise or double detections in Gaia (the Varstrometry for Off-nucleus and Dual sub-Kpc AGN (VODKA) project). From this follow-up, we spectroscopically identify 11 star superpositions and seven dual/lensed quasars. Among the remaining targets, two are likely dual/lensed quasars based on additional radio imaging, while the rest are quasars with unknown companions. Without prior photometric or spectroscopic selection, we find the star contamination rate to be 41%–67%, while the dual/lensed quasar fraction is ≳26% in the follow-up VODKA sample. However, when combined with existing unresolved spectra and spatially resolved two-band color cuts, the dual/lensed quasar fraction can be increased to ≳67%. Our study highlights the need for high-quality spectral data, including a signal-to-noise ratio of at least 20, spatial resolution that is at least twice finer than the source separation, and a spectral resolution of R ≳ 1000, in order to separate close sources, exclude stellar superpositions, and reliably identify dual quasars.

Dwarf galaxies (DGs) are thought of as the building blocks of large galaxies such as our Milky Way. This paper presents new high-resolution hydrodynamical simulations of DGs and their intergalactic medium with the GIZMO code. Our simulations consider the key physical processes of galaxy evolution, such as gas cooling, chemistry, and stellar and black hole feedback. Unlike previous work, the initial conditions of our simulations take DGs of 2–5 × 10¹⁰M_⊙ from the realistic cosmology simulations of IllustrisTNG. We further increase the original resolution of IllustrisTNG by a factor of ∼100 via a particle-splitting scheme. Our results show that the evolution of the complex multiphase circumgalactic medium (CGM) and its metal content is sensitive to the redshift of DGs. The accretion of the CGM into DGs plays a key role, providing 20%–50% of the star-forming gas and replenishing 40%–70% of the total mass in the galactic disk. Furthermore, the accretion histories of the supermassive black holes (SMBHs) at the centers of high-z DGs shows episodic patterns, with high-accreting states close to ∼10% of the Eddington mass accretion rate, implying the rapid growth of SMBHs in the early Universe, which may be revealed by coming observations from the James Webb Space Telescope.

The mid-M star TOI 1227 hosts among the youngest known transiting exoplanets. We have conducted new X-ray imaging and optical spectroscopic observations of TOI 1227 aimed at ascertaining its age and the influence of its high-energy radiation on the exoplanet, TOI 1227b. We obtained a definitive X-ray detection of TOI 1227 with the Chandra/High Resolution Camera-I (HRC-I), and measured its Li and Hα lines using the Australian National University’s Siding Spring Observatory 2.3 m telescope (WiFeS) spectroscopy. Through spatiokinematic, isochronal, and spectral energy distribution-based modeling, we have constrained the age of TOI 1227 as lying between 5 and 12 Myr, with a best estimate of ∼8 Myr. In the context of this age, we model the evolution of the transiting exoplanet TOI 1227b, using the X-ray luminosity derived from Chandra HRC-I imaging. Our modeling suggests that TOI 1227b is currently undergoing rapid atmospheric mass loss at rates on the order of ∼10¹² g s⁻¹. The modeling demonstrates that the exoplanet’s predicted future evolution depends sensitively on assumptions for total and core planet mass, highlighting the importance of follow-up observations of the TOI 1227 star–exoplanet system to enable measurements of both planetary mass and mass-loss rate.

Classical Ae (CAe) stars are main-sequence, A-type stars with Hα emission but no signature of dust. They are thought to be the cool extension of the classical Be stars to lower masses. Recent surveys based on Hα spectroscopy have significantly increased the number of known CAe stars, with the population extending to spectral types as cool as A4 (T_eff ≈ 8500 K). We compute the temperature structure of gaseous, circumstellar disks around A-type stars, including both radiative heating from the central star and viscous shear heating from the disk’s rotation. We find that shear heating can become important for spectral types A2 and later and can act to increase the low temperatures predicted by purely radiatively heated disks. Our modeling indicates that the presence and strength of Hα emission for spectral types A2 and later significantly increases with the amount of shear heating included, and we propose that this dependence can be used to constrain the α viscosity parameter appropriate for CAe star disks.

We present simple analytic corrections to the standard blackbody fitting used for early kilonova emission. We consider a spherical, relativistically expanding shell that radiates thermally at a single temperature in its own rest frame. Due to relativistic effects, including Doppler boosting, time delay, and temperature evolution, the observed temperature is smeared across different polar angles by approximately ∼10%. While the observed spectrum remains roughly consistent with a single-temperature blackbody, neglecting relativistic effects leads to significant systematic inaccuracies: the inferred photospheric velocity and temperature are overestimated by up to ∼50% for mildly relativistic velocities. By applying our analytic corrections, these deviations are reduced to within 10%, even in cases where the photosphere is receding and cooling is considered. Applying our corrections to observed kilonovae (AT2017gfo and the thermal component of GRB 211211A) reveals that standard blackbody fitting overestimated the inferred velocities and temperatures by 10%–40%; such deviations can alter the inferred formation of heavy elements.

We present the radio continuum counterparts to the enigmatic ultracompact X-ray binaries (UCXBs): a black hole or neutron star accreting from a hydrogen-deficient white dwarf donor star with short orbital periods (<80 minutes). For the sample of UCXBs hosted by globular clusters (GCs), we search for whether certain GC properties are more likely to enhance UCXB formation. We determine that GCs that host UCXBs are drawn from a distinct population in terms of cluster concentration, core radius, and half-light radius, but are similar to other well-studied GCs in metallicity and cluster mass. In particular, UCXB-hosting GCs tend to be on average more compact, with a higher concentration than other GCs, with significantly higher encounter rates. We investigate whether a correlation exists between radio luminosity and orbital period, using new and archival observations. We determine that there is not a clear connection between the two observable quantities.

Turbulence governs the fragmentation of molecular clouds and plays a pivotal role in star formation. The persistence of observed cloud turbulence suggests it does not decay significantly within the turnover timescale, implying a recurrent driving mechanism. Although ubiquitous self-gravity is a plausible driver, magnetohydrodynamic simulations by E. C. Ostriker et al. in 2001 demonstrated that self-gravity alone does not modify the global turbulence decay rate. In this study, we demonstrate that the dominant diffuse volume of a cloud dictates its overall decay rate, while individual dense cores can maintain near-zero decay rates. Crucially, this phenomenon is absent in control simulations excluding self-gravity. This discrepancy cannot be attributed to contamination of turbulent velocities by core contraction because most cores in our simulations remain in a quasi-equilibrium state. Our analysis reveals that the gravitational potential energy released during core formation—not necessarily driven by self-gravity but also by turbulent compression—is sufficient to sustain the observed turbulence levels within cores.

Coronal plumes are narrow, collimated structures that are primarily viewed above the solar poles and in coronal holes in the extreme ultraviolet, but also in sunspots. Open questions remain about plume formation, including the role of small-scale transients and whether plumes embedded in different magnetic field configurations have similar formation mechanisms. We report on coordinated Solar Orbiter/Extreme Ultraviolet Imager (EUI), Interface Region Imaging Spectrograph, and Solar Dynamics Observatory observations of the formation of a plume in sunspot penumbra in 2022 March. During this observation, Solar Orbiter was positioned near the Earth–Sun line and EUI observed at a 5 s cadence with a spatial scale of 185 km pixel⁻¹ in the solar corona. We observe fine-scale dots at various locations in the sunspot, but the brightest and highest density of dots is at the plume base. Space-time maps along the plume axis show parabolic and V-shaped patterns, and we conclude that some of these dots are possible signatures of magneto-acoustic shocks. Compared to other radial cuts around the sunspot, along the plume shows the longest periods (∼7 minutes) and the most distinct tracks. Bright dots at the plume base are mostly circular and do not show elongations from a fixed origin, in contrast to jetlets and previously reported penumbral dots. We do not find high-speed, repeated downflows along the plume, and the plume appears to brighten coherently along its length. Our analysis suggests that jetlets and downflows are not a necessary component of this plume’s formation, and that mechanisms for plume formation could be dependent on magnetic topology and the chromospheric wave field.

Higher-order finite volume schemes for magnetohydrodynamics (MHD) and relativistic magnetohydrodynamics (RMHD) are very valuable because they allow us to carry out astrophysical simulations with very high accuracy. However, astrophysical problems sometimes have unusually large Mach numbers, exceptionally high Lorentz factors, and very strong magnetic fields. All these effects cause higher-order codes to become brittle and prone to code crashes. In this paper, we document physical constraint preserving (PCP) methods for treating numerical MHD and RMHD. While unnecessary for standard problems, for stringent astrophysical problems, these methods show their value. We describe higher-order methods that allow divergence-free evolution of the magnetic field. We present a novel two-dimensional Riemann solver. This two-dimensional Riemann solver plays a key role in the design of PCP schemes for MHD and RMHD. We present a very simple PCP formulation and show how it is amalgamated with the evolution of face-centered magnetic fields. The methods presented here are time-explicit and do not add much to the computational cost. We show that the methods meet their design accuracies and work well on problems that would otherwise be considered too extreme for typical higher-order Godunov methods of the type used in computational astrophysics.

We identify a sample of 234 dusty star-forming galaxies (DSFGs) in the A2744 and GOODS-S fields using JWST/NIRCam-selected galaxies as priors for SCUBA-2 measurements. This method provides a large number of galaxies both above an 850 μm flux of 2 mJy (47 bright DSFGs) and below (187 faint DSFGs), representing the largest sample of individually identified (i.e., not stacked) faint DSFGs to date. We observe that f_F444W and f_F150W are tightly correlated with redshift, with fainter sources lying at higher redshifts, suggesting that the observed near-IR flux may be an effective way of selecting high-redshift DSFGs. We study the physical properties and morphologies of the DSFGs through spectral energy distribution fitting and parametric surface brightness profile modeling. Other than the lower star formation rates (SFRs) and total infrared luminosities in the faint DSFGs (SFR ; ) compared to the bright DSFGs (SFR ; ), the populations have similar properties. The stellar masses do not appear to be strongly dependent on either the SFRs or the submillimeter flux. These results suggest that the faint DSFGs are drawn from the same population of galaxies as the bright DSFGs. Based on visual inspections, we find a lower merger fraction (∼21%) relative to previous Hubble Space Telescope–based studies, suggesting that dust attenuation may have impacted previous estimates of DSFG merger rates.

The two massive galaxies in the Local Group both host substantially fewer satellites than the subhalos expected from the cold dark matter paradigm, and recent investigations have highlighted the interplay between baryons and dark matter. We investigate the processes that make subhalos starless, using high-resolution cosmological simulations. We find that the number of satellites around Milky Way analogs closely aligns with observations, which accords with recent studies. In our simulations, the majority of subhalos are devoid of stars, i.e., “starless.” We first examined supernova feedback and the environmental effects associated with subhalos’ orbital motion as candidates for their origin. However, neither seems to be the main driver. Supernova feedback causes a reduction in cold gas in “starred” subhalos, but its impact is not significant. In the case of starless subhalos, supernova feedback is irrelevant because most of them do not have in situ star formation in the first place. The orbital motion in dense environments causes the removal of gas in all subhalos, but it is not enough to remove preexisting stars. The key is found to be the effect of reionization instead. Starless subhalos are initially born in regions that are less efficient in accreting matter. This makes them lack sufficiently dense gas to self-shield from UV background heating, preventing their gas from cooling below the star formation threshold. This indicates that starless subhalos are not made but born.

In the past two decades, transit surveys have revealed a class of planets with thick atmospheres—sub-Neptunes—that must have completed their accretion in protoplanet disks. When planets form in the gaseous disk, the gravitational interaction with the disk gas drives their migration and results in the trapping of neighboring planets in mean motion resonances, though these resonances can later be broken when the damping effects of disk gas or planetesimals wane. It is widely accepted that the outer solar system gas-giant planets originally formed in a resonant chain, which was later disrupted by dynamical instabilities. Here, we explore whether the early formation of the terrestrial planets in a resonance chain (including Theia) can evolve to the present configuration. Using N-body simulations, we demonstrate that the giant planet instability would also have destabilized the terrestrial resonance chain, triggering Moon-forming giant impacts in 20%–50% of our simulated systems, dependent on the initial resonance architecture. After the instability, the eccentricity and inclination of the simulated planets match their present-day values. Under the proposed scenario, the current period ratio of 3.05 between Mars and Venus—devoid of any special significance in traditional late-formation models—naturally arises as a relic of the former resonance chain.

The advent of large integral field spectroscopic surveys has found that elliptical galaxies (EGs) can be divided into two classes: the fast rotators (whose kinematics are dominated by rotation) and the slow rotators (which exhibit slow or no rotation pattern). It is often suggested that while the slow rotators typically have boxy isophotal shapes, have a high α-to-iron abundance ratio, and are quite massive, the fast rotators often exhibit the opposite properties (that is, having disky isophotes, lower α-to-iron ratio, and of typical masses). Whether the EGs consist of two distinct populations (i.e., a dichotomy exists) remains an unsolved issue. To examine the existence of the dichotomy, we used a sample of 1895 EGs from the SDSS-IV MaNGA survey and measured robustly the stellar kinematics, isophotal shapes, and [Mg/Fe] ratio. We confirmed the previous finding that the bulk of the EGs are disky (65%) and fast rotators (67%), but we found no evidence supporting a dichotomy, based on a principal component analysis. The different classes (boxy/disky and slow/fast rotators) of EGs occupy slightly different loci in the principal component space. This may explain the observed trends that led to the premature support of a dichotomy based on small samples of galaxies.

We introduce the Spectroscopy Pre-trained Transformer (SpecPT), a transformer-based model designed to analyze spectroscopic data, with applications in spectrum reconstruction and redshift measurement. Using the Early Data Release (EDR) of the Dark Energy Spectroscopic Instrument (DESI) survey, we evaluate SpecPT’s performance on two distinct data sets: the Bright Galaxy Survey (BGS) and Emission Line Galaxy (ELG) samples. SpecPT successfully reconstructs spectra, accurately capturing emission lines, absorption features, and continuum shapes while effectively reducing noise. For redshift prediction, SpecPT achieves competitive accuracy, with normalized median absolute deviation values of 0.0006 and 0.0008, and catastrophic outlier fractions of 0.20% and 0.80% for BGS and ELG, respectively. Notably, SpecPT performs consistently well across the full redshift range (0 < z < 1.6), demonstrating its versatility and robustness. By leveraging its learned latent representations, SpecPT lays the groundwork for a foundational spectroscopic model, with potential applications in outlier detection, interstellar medium property estimation, and transfer learning to other data sets. This work represents a first step in building a generalized framework for spectroscopic analysis, capable of scaling to the full DESI data set and beyond.

Stellar oscillation codes are software instruments that evaluate the normal-mode frequencies of an input stellar model. While inter-code comparisons are often used to confirm the correctness of calculations, they are not suitable for characterizing the numerical error of an individual code. To address this issue, we introduce a set of tools—“error measures”—that facilitate this characterization. We explore the behavior of these error measures as calculation parameters, such as the number of radial grid points used to discretize the oscillation equations, are varied, and we summarize this behavior via an idealized error model. While our analysis focuses on the GYRE code, it remains broadly applicable to other oscillation codes.

The recent IceCube detection of TeV neutrino emission from the nearby active galaxy NGC 1068 suggests that active galactic nuclei (AGNs) could make a sizable contribution to the diffuse flux of astrophysical neutrinos. The absence of TeV γ-rays from NGC 1068 indicates neutrino production in the vicinity of the supermassive black hole, where the high radiation density leads to γ-ray attenuation. Therefore, any potential neutrino emission from similar sources is not expected to correlate with high-energy γ-rays. Disk-corona models predict neutrino emission from Seyfert galaxies to correlate with keV X-rays because they are tracers of coronal activity. Using through-going track events from the Northern Sky recorded by IceCube between 2011 and 2021, we report results from a search for individual and aggregated neutrino signals from 27 additional Seyfert galaxies that are contained in the Swift's Burst Alert Telescope AGN Spectroscopic Survey. Besides the generic single power law, we evaluate the spectra predicted by the disk-corona model assuming stochastic acceleration parameters that match the measured flux from NGC 1068. Assuming all sources to be intrinsically similar to NGC 1068, our findings constrain the collective neutrino emission from X-ray bright Seyfert galaxies in the northern sky, but, at the same time, show excesses of neutrinos that could be associated with the objects NGC 4151 and CGCG 420-015. These excesses result in a 2.7σ significance with respect to background expectations.

In S. J. Hollick et al., we surveyed the Voyager magnetic field data from launch through 1990 where the Voyagers 1 and 2 spacecraft reach 43.5 au and 33.6 au, respectively. We identified 637 intervals of wave activity that could be attributed to either interstellar pickup He⁺, H⁺, or both. In our quest to identify and study low-frequency magnetic waves arising from interstellar pickup H⁺, we found 19 intervals, 16 with thermal ion data, within ∼3 au. We compared the growth rate of the waves with the rate of background turbulence they must overcome to reach observable levels. Ionization of interstellar neutral H is highly efficient, resulting in a factor of 10 reduction in density by 1 au relative to values at R > 10 au. At the same time, solar wind turbulence increases with decreasing distance to the Sun. This makes it unlikely that interstellar neutral hydrogen can penetrate within ∼3 au in sufficient number to explain the wave observations seen by the Voyager magnetometers. We consider the possibility that the so-called “inner source” for pickup H⁺ arising from the interaction of solar wind protons with dust grains may account for the density of newborn pickup ions required for the growth of the observed waves. Although the Voyagers lack the instrumentation required to measure pickup ions, we do conclude that the inner-source theories provide a compelling explanation for the majority of the observations while it is possible that a few could be due to either interstellar ions or shocks.

X-ray observing facilities, such as the Chandra X-ray Observatory and the eROSITA, have detected over a million astronomical sources associated with high-energy phenomena. The arrival of photons as a function of time follows a Poisson process and can vary by orders-of-magnitude, presenting obstacles for common tasks such as source classification, physical property derivation, and anomaly detection. Previous work has either failed to directly capture the Poisson nature of the data or only focuses on Poisson rate function reconstruction. In this work, we present the Poisson Process AutoDecoder (PPAD), which is a neural field decoder that maps fixed-length latent features to continuous Poisson rate functions across energy band and time via unsupervised learning. PPAD reconstructs the rate function and yields a representation at the same time. We demonstrate the efficacy of PPAD via reconstruction, regression, classification, and anomaly detection experiments using the Chandra Source Catalog.

To accelerate cosmic rays (CRs) to ∼PeV energies, diffusive shock acceleration (DSA) in Galactic supernova remnants requires amplified magnetic turbulence in the shock to facilitate broadband Bohm diffusion of CRs. Recent particle-in-cell (PIC) shock simulations suggest that diffusion may be driven by short large-amplitude magnetic structures (SLAMS). Persistent SLAMS develop in the upstream of shocks with an Alfvénic Mach number M_A ≳ 20 via the Bell instability and nonlinear amplification/steepening. We employ test-particle simulations to examine particle transport and acceleration in model shocks populated by analytically prescribed, idealized SLAMS that approximate the magnetic structures of PIC shock simulations. We demonstrate that SLAMS drive broadband Bohm diffusion of magnetized electrons (i.e., electron Larmor radius r_L ≪  magnetic-structure length λ_AM) and unmagnetized electrons (i.e., r_L ≫ λ_AM). We show that SLAMS accelerate unmagnetized electrons via DSA, and magnetized electrons via shock drift acceleration (SDA) and quasi-periodic shock acceleration (QSA). QSA, a novel Fermi-type mechanism, proceeds via rapid scattering in the converging flow between the first upstream magnetic structure and the near-downstream, shock-amplified field. QSA becomes vital for maintaining electron acceleration in shocks with superluminal SLAMS, which strongly advect magnetized electrons due to high inclination between field lines and the flow. We find that test-electron spectra are consistent with spectra from PIC simulations, indicating that the test-particle method can be used to extrapolate PIC results to longer spatial and temporal scales. Overall, our results suggest that SLAMS in M_A ≳ 20 shocks may play an important role in facilitating shock acceleration.