Table of contents for issue 1, volume 989, The Astrophysical Journal

We present the Atacama Large Millimeter/submillimeter Array Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO), a large program of the ALMA. AGE-PRO aims to systematically trace the evolution of gas disk mass and size throughout the lifetime of protoplanetary disks. It uses a carefully selected sample of 30 disks around M3-K6 stars in three nearby star-forming regions: Ophiuchus (0.5–1 Myr), Lupus (1–3 Myr), and Upper Sco (2–6 Myr). Assuming the three regions had similar initial conditions and evolutionary paths, we find the median gas disk mass appears to decrease with age. Ophiuchus disks have the highest median gas mass (6 M_Jup), while the Lupus and Upper Sco disks have significantly lower median masses (0.68 and 0.44 M_Jup, respectively). Notably, the gas and dust disk masses appear to evolve on different timescales. This is evidenced by the median gas-to-dust mass ratio, which decreases from 122 in the youngest disks (<1 Myr) to 46 in Lupus disks, and then increases to 120 in the Upper Sco disks. The median gas disk sizes range between 74 and 110 au, suggesting that typical gas disks are much smaller than those of well-studied, massive disks. Population synthesis models suggest that magnetohydrodynamic wind-driven accretion can reproduce median disk properties across all three regions, when assuming compact disks with a declining magnetic field over time. In contrast, turbulent-driven models overestimate gas masses of >1 Myr disks by an order of magnitude. Here, we discuss the program’s motivation, survey design, sample selection, observation and data calibration processes, and highlight the initial results.

The ALMA survey of Gas Evolution in PROtoplanetary disks (AGE-PRO) Large Program aims to trace the evolution of gas disk mass and size throughout the lifetime of protoplanetary disks by using the Atacama Large Millimeter/submillimeter Array (ALMA). This paper presents Band-6 ALMA observations of 10 embedded (Class I and Flat Spectrum) sources in the Ophiuchus molecular cloud, with spectral types ranging from M3 to K6 stars, which serve as the evolutionary starting point in the AGE-PRO sample. While we find four nearly edge-on disks (≥70°), and three highly inclined disks (≥60°) in our sample, we show that, as a population, embedded disks in Ophiuchus are not significantly contaminated by more-evolved, but highly inclined sources. We derived dust disk masses from the Band-6 continuum and estimated gas disk masses from the C¹⁸O J = 2−1 and C¹⁷O J = 2−1 lines. The mass estimates from the C¹⁷O line are slightly higher, suggesting C¹⁸O emission might be partially optically thick. While the ¹²CO and ¹³CO lines are severely contaminated by extended emission and self-absorption, the C¹⁸O and C¹⁷O lines are allowed to trace the radial extent of the gaseous disks. From these measurements, we found that the C¹⁸O J = 2−1 and C¹⁷O J = 2−1 fluxes correlate well with each other and with the continuum fluxes. Furthermore, the C¹⁸O and C¹⁷O lines present a larger radial extension than disk dust sizes by factors ranging from ∼1.5 to ∼2.5, as is found for Class II disks using the radial extension of the ¹²CO. In addition, we have detected outflows in three disks from ¹²CO observations.

We present Band 6 and Band 7 observations of 10 Lupus disks around M3-K6 stars from the Atacama Large Millimeter/submillimeter Array survey of Gas Evolution in PROtoplanetary disks (AGE-PRO) Large Program. In addition to continuum emission in both bands, our Band 6 setup covers the ¹²CO, ¹³CO, and C¹⁸O J = 2–1 lines, while our Band 7 setup covers the N₂H⁺J = 3–2 line. All of our sources are detected in ¹²CO and ¹³CO; seven out of ten are detected in C¹⁸O; and three are detected in N₂H⁺. We find strong correlations between the CO isotopologue line fluxes and the continuum flux densities. With the exception of one disk, we also identify a strong correlation between the C¹⁸O J = 2–1 and N₂H⁺J = 3–2 fluxes, indicating similar CO abundances across this sample. For the two sources with well-resolved continuum and ¹²CO J = 2–1 images, we find that their gas-to-dust size ratio is consistent with the median value of ∼2 inferred from a larger sample of Lupus disks. We derive dust disk masses from continuum flux densities. We estimate gas disk masses by comparing C¹⁸O J = 2–1 line fluxes with those predicted by the limited grid of self-consistent disk models of M. Ruaud et al. A comparison of these mass estimates with those derived by L. Trapman et al., using a combination of CO isotopologue and N₂H⁺ line emission, shows that the masses are consistent with each other. Some discrepancies appear for small and faint disks, but they are still within the uncertainties. Both methods find gas disk masses increase with dust disk masses, and gas-to-dust mass ratios are between 10 and 100 in the AGE-PRO Lupus sample.

The Atacama Large Millimeter/submillimeter Array (ALMA) large program AGE-PRO explores protoplanetary disk evolution by studying gas and dust across various ages. This work focuses on 10 evolved disks in Upper Scorpius, observed in dust continuum emission, CO and its isotopologues, and N₂H⁺ with ALMA Bands 6 and 7. Disk radii, from the radial location enclosing 68% of the flux, are comparable to those in the younger Lupus region for both gas and dust tracers. However, solid masses are about an order of magnitude below those in Lupus and Ophiuchus, while the dust spectral index suggests some level of dust evolution. These empirical findings align with a combination of radial drift, dust trapping, and grain growth into larger bodies. A moderate correlation between CO and continuum fluxes suggests a link between gas and dust content, through the increased scatter compared to younger regions, possibly due to age variations, gas-to-dust ratio differences, or CO depletion. Additionally, the correlation between C¹⁸O and N₂H⁺ fluxes observed in Lupus persists in Upper Scorpius, indicating a relatively stable CO gas abundance over the Class II stage of disk evolution. In conclusion, the AGE-PRO survey of Upper Scorpius disks reveals intriguing trends in disk evolution. The findings point toward potential gas evolution and the presence of dust traps in these older disks. Future high-resolution observations are needed to confirm these possibilities and further refine our understanding of disk evolution and planet formation in older environments.

The evolution of the gas mass of planet-forming disks around young stars is crucial for our understanding of planet formation, yet it has proven hard to constrain observationally, due both to the difficulties of measuring gas masses and the lack of a homogeneous sample. Here we present a large grid of thermochemical models that we use to measure protoplanetary gas disk masses of AGE-PRO, the Atacama Large Millimeter/submillimeter Array survey of Gas Evolution in PROtoplanetary disks. AGE-PRO covers a sample of 30 disks around similar spectral type (M3-K6) stars with ages between 0.1 and 10 Myr. Our approach is to simultaneously fit observations of CO isotopologues and N₂H⁺, a complementary molecule produced when CO freezes out. We find that the median gas mass of the three regions decreases over time, from in Ophiuchus (≲1 Myr) to for Lupus (∼1–3 Myr) and for Upper Sco (∼2–6 Myr), with ∼1 dex scatter in gas mass in each region. We note that the gas mass distributions for Lupus and Upper Sco look very similar, which could be due to survivorship bias for the latter. The median bulk CO abundance in the CO emitting layer is found to be a factor ∼10 lower than the interstellar medium value but does not significantly change between Lupus and Upper Sco. From Lupus to Upper Sco, the median gas-to-dust mass ratio increases by a factor ∼3 from ∼40 to ∼120, suggesting efficient inward pebble drift and/or the formation of planetesimals.

The potential for planet formation of a circumstellar disk depends on the dust and gas reservoirs, which evolve as a function of the disk age. The Atacama Large Millimeter/submillimeter Array AGE-PRO Large Program has measured several disk properties across three star-forming regions of different ages, and in this study, we compare the observational results to dust evolution simulations. Using DustPy for the dust evolution, and RADMC-3D for the radiative transfer, we ran a large grid of models spanning stellar masses of 0.25, 0.50, 0.75, and 1.0 M_⊙, with different initial conditions, including: disk sizes, disk gas masses, and dust-to-gas ratio, and viscosity. Our models are performed assuming smooth, weakly, or strongly substructured disks, aiming to investigate if any observational trend can favor or exclude the presence of dust traps. The observed gas masses in the disks of the AGE-PRO sample are not reproducible with our models, which only consider viscous evolution with constant α, suggesting that additional physical mechanisms play a role in the evolution of the gas mass of disks. When comparing the dust continuum emission fluxes and sizes at 1.3 mm, we find that most of the disks in the AGE-PRO sample are consistent with simulations that have either weak or strong dust traps. The evolution of spectral index in the AGE-PRO sample is also suggestive of an unresolved population of dust traps. Future observations at high angular resolution are still needed to test several hypotheses that result from comparing the observations to our simulations, including that more massive disks in gas mass have the potential to form dust traps at larger disk radii.

The architecture of planetary systems depends on the evolution of the disks in which they form. In this work, we develop a population synthesis approach to interpret the Atacama Large Millimeter/submillimeter Array survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO) measurements of disk gas mass and size considering two scenarios: turbulence-driven evolution with photoevaporative winds and MHD wind-driven evolution. A systematic method is proposed to constrain the distribution of disk parameters from the disk fractions, accretion rates, disk gas masses, and CO gas sizes. We find that turbulence-driven accretion with initially compact disks (R₀ ≃ 5–20 au), low mass-loss rates, and relatively long viscous timescales (t_ν,0 ≃ 0.4–3 Myr or α_SS ≃ 2–4 × 10⁻⁴) can reproduce the disk fractions and gas sizes. However, the distribution of apparent disk lifetimes defined as the ratio is severely overestimated by turbulence-driven models. On the other hand, MHD wind-driven accretion can reproduce the bulk properties of disk populations from Ophiuchus to Upper Scorpius assuming compact disks with an initial magnetization of about β ≃ 10⁵ (α_DW ≃ 0.5–1 × 10⁻³) and a magnetic field that declines with time. More studies are needed to confirm the low masses found by AGE-PRO, notably for compact disks that question turbulence-driven accretion. The constrained synthetic disk populations can now be used for realistic planet population models to interpret the properties of planetary systems on a statistical basis.

Protoplanetary disk evolution can be deeply influenced by the UV radiation emitted by neighboring massive stars (mainly of spectral types O and B). We show that the process of external photoevaporation, which causes an outside-in depletion of disk material due to environmental UV radiation, can lead to a significant decrease in disk size, disk mass, and lifetime even at moderate irradiation levels (1–10 G₀). In this work, we investigate the role of external photoevaporation in shaping the masses and sizes of the 10 AGE-PRO disks in the Upper Scorpius (Upper Sco) region, which we estimate to be subject to far-ultraviolet (FUV) fluxes ranging between ∼2 and ∼12 G₀, on average. We compare the disk masses and sizes resulting from 1D numerical viscous evolution simulations, in which the effect of external photoevaporation is included, to the values retrieved from the AGE-PRO observations. While the pure viscous framework fails in adequately explaining the observed disk properties in Upper Sco, with the inclusion of external photoevaporation, we can successfully reproduce gas disk sizes for seven out of 10 sources within a factor <2, when the initial disk mass is 1%–10% of the stellar mass. We emphasize the importance of accounting for the environmental irradiation when comparing star-forming regions of different ages, even when moderate FUV irradiation fields are experienced, as in the case of Upper Sco.

We perform visibility fitting to the dust continuum Band 6 1.3 mm data of the 30 protoplanetary disks in the Atacama Large Millimeter/submillimeter Array Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO) Large Program. We obtain disk geometries, dust-disk radii, and azimuthally symmetric radial profiles of the intensity of the dust continuum emission. We examine the presence of continuum substructures in the AGE-PRO sample by using these radial profiles and their residuals. We detect substructures in 15 out of 30 disks. We report five disks with large (>15 au) inner dust cavities. The Ophiuchus Class I disks show dust-disk substructures in ∼80% of the resolved sources. This evidences the early formation of substructures in protoplanetary disks. A spiral is identified in IRS 63, hinting to gravitational instability in this massive disk. We compare our dust-disk brightness radial profiles with gas-disk brightness radial profiles and discuss colocal substructures in both tracers. In addition, we discuss the evolution of dust-disk radii and substructures across Ophiuchus, Lupus, and Upper Scorpius. We find that disks in Lupus and Upper Scorpius with large inner dust cavities have typical gas-disk masses, suggesting an abundance of dust cavities in these regions. The prevalence of pressure dust traps at later ages is supported by a potential trend with time with more disks with large inner dust cavities (or transition disks) in Upper Scorpius and the absence of evolution of dust-disk sizes with time in the AGE-PRO sample. We propose this is caused by an evolutionary sequence with a high fraction of protoplanetary disks with inner protoplanets carving dust cavities.

The inward drift of millimeter–centimeter sized pebbles in protoplanetary disks has become an important part of our current theories of planet formation and, more recently, planet composition as well. The gas-to-dust size ratio of protoplanetary disks can provide an important constraint on how pebbles have drifted inward, provided that observational effects, especially resolution, can be accounted for. Here we present a method for fitting beam-convolved models to integrated intensity maps of line emission using the astropy Python package and use it to fit ¹²CO moment zero maps of 10 Lupus and 10 Upper Scorpius protoplanetary disks from the ALMA Survey of Gas Evolution of PROtoplanetary Disks (AGE-PRO) Program, a sample of disks around M3-K6 stars that cover the  ∼1–6 Myr of gas disk evolution. From the unconvolved best fit models, we measure the gas disk size (), which we combine with the dust disk size () from continuum visibility fits from M. Vioque et al. to compute beam-corrected gas-to-dust size ratios. In our sample, we find gas-to-dust size ratios between  ∼1 and  ∼5.5, with a median value of . Contrary to models of dust evolution that predict an increasing size ratio with time, we find that the younger disks in Lupus have similar (or even larger) median ratios than the older disks in Upper Sco . A possible explanation for this discrepancy is that pebble drift is halted in dust traps combined with truncation of the gas disk by external photoevaporation in Upper Sco, although survivorship bias could also play a role.

Variability of millimeter wavelength continuum emission from Class II protoplanetary disks is extremely rare, and when detected, it is usually interpreted as originating from nonthermal emission mechanisms that relate to the host star itself rather than its disk. During observations made as part of the AGE-PRO Large Program, significant variability in the brightness of the 2MASS J16202863-2442087 system was detected between individual executions. We report the observed properties of the variability detected at millimeter wavelengths and investigate potential driving mechanisms. To investigate the nature of the variability, we construct a light curve from the continuum observations and analyze images constructed from both flaring and quiescent emission. We characterize the dust disk around the star through analysis in the image and visibility plane, and carry out kinematic analysis of CO (2–1) emission from the gas disk. The continuum flux decays by a factor of 8 in less than an hour, and by a factor of 13 within 8 days. The peak brightness coincides with an expected brightness maximum extrapolated from the periodicity of previously observed optical variability. The flare is most likely the product of synchrotron emission in the close vicinity of the star. The nature of the millimeter flare closely resembles those detected in very close binary systems, and may be due to the interaction of magnetic fields in an as-yet undetected binary. Alternatively, if the central host is a single-star object, the flare may be due to the interaction of magnetic field loops at the stellar surface or a strong accretion burst.

We identify stellar tidal debris from the ω Centauri (ω Cen) system among field stars in the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey via chemical tagging using a neural network trained on APOGEE observations of the ω Cen core. We find a total of 463 ω Cen debris candidates have a probability P > 0.8 of sharing common patterns in their chemical abundances across a range of individual elements or element combinations, including [C+N], O, Mg, Al, Si, Ca, Ni, and Fe. Some debris candidates show prograde or retrograde disk-like kinematics, but most show kinematics consistent with the accreted halo, showing high radial actions, J_R, values. We find that a sample of Gaia-Sausage-Enceladus (GES) members are chemically distinct from the ω Cen core, suggesting that ω Cen is associated with an independent merger event shaping the Milky Way halo. However, a connection between GSE and ω Cen cannot be ruled out. A detailed comparison with N-body simulations indicates that the ω Cen progenitor was a massive dwarf galaxy (≳10⁸M_⊙). The existence of a metal-poor high-α chemically homogeneous halo debris is also reported.

Quasiperiodic eruptions (QPEs) are repeating soft-X-ray bursts from the nuclei of galaxies, tantalizingly proposed to be extreme-mass-ratio inspirals. Here, we report the discovery of a new galaxy showing X-ray QPEs, the fifth found through a dedicated blind search of the Spectrum–Roentgen–Gamma/eROSITA all-sky survey data, hereafter named eRO-QPE5. Its QPE duration (t_dur ∼ 0.6 days), recurrence time (t_recur ∼ 3.7 days), integrated energy per eruption (∼3.4 × 10⁴⁷ erg), and black hole mass () sit at the high end of the known population. Like other eROSITA or X-ray-discovered QPEs, no previous or concurrent optical–IR transient is found in archival photometric data sets, and the optical spectrum looks almost featureless. With a spectroscopic redshift of 0.1155, eRO-QPE5 is the most distant QPE source discovered to date. Given the number of recent discoveries, we test for possible correlations and confirm a connection between t_dur and t_recur, while we do not find any significant correlation involving either M_BH or the QPE temperature. The slope of the t_dur–t_recur relation (1.14 ± 0.16) is roughly consistent with predictions from star–disk collision models, with a preference for those suggesting that QPEs are powered by stellar debris streams around the orbiter. Considering this and previous discoveries, eROSITA has proved extremely successful in finding many QPE candidates, given its grasp—namely, its its sensitivity and large field of view—and scanning capabilities over the full sky. We advocate the need for sensitive wide-area- and time-domain-oriented surveys from future-generation soft-X-ray missions.

In this paper we introduce a method for resolving multiparameter likelihoods by fixing all parameter values but two. Evaluation of those two variables is followed by iteratively cycling through each of the parameters in turn until convergence. We test the technique on the temperature power spectrum of the lensed cosmic microwave background. That demonstration is particularly effective since one of the six parameters that define the power spectra, the power spectrum amplitude, A_s, nears linearity at small deviations, reducing computation to incrementation in one dimension, rather than over a two-dimensional (2D) grid. At each iterative step A_s is paired with a different parameter. The iterative process yields parameter values in agreement with those derived by Planck, and results are obtained within a few hundred calls for spectra. We further compute parameter values as a function of maximum multipole, ℓ_max, spanning a range from ℓ_max = 959 to 2500 and uncover bimodal behavior at the lower end of that range. In the general case, in which neither variable is linear, we identify moderating factors, such as changing both parameters per each iterative step, and thereby reducing the number of steps per iteration. Markov Chain Monte Carlo (MCMC) computation has been the dominant instrument for evaluating multiparameter functions. For applications with a quasi-linear variable such as, A_s, the 2D iterative method is orders of magnitude more efficient than MCMC.

We report the detection of 167 bursts from an active repeater, FRB 20240114A, using the upgraded Giant Metrewave Radio Telescope. The observations were carried out over a frequency range of 300–750 MHz, and on four different dates over a period of 6 months. Our analysis indicates that the fast radio bursts' emission properties are evolving, with both the median flux and emission rate of the bursts decreasing over time. The properties of the bursts also vary widely, with a wide range of intrinsic widths (0.246–39.364 ms), scattering timescales (0.004–28.289 ms), dispersion measures (524.07–533.56 pc cm⁻³), and band occupancies (9–180 MHz). The distribution for the waiting time, t_wait, is bimodal, and follows a Weibull distribution, with a shape parameter k = 0.33; however, when the two distributions are fit separately, they follow a Weibull distribution with k = 0.63 for t_wait < 1 s, and a log-normal distribution with a width of σ = 1.28 for t_wait > 1 s. The isotropic energy distribution is seen to follow a log-normal distribution as well, with a width of σ = 0.83.

We present a statistical approach to investigating the dynamical evolution of the old open cluster Trumpler 19. We identified 810 cluster members using an ensemble-based unsupervised machine learning method applied to Gaia Data Release 3 astrometric data. From the color–magnitude diagram, we identified 18 blue straggler stars (BSSs) in Trumpler 19. The mass function of the cluster shows a flatter slope, indicating strong mass segregation and advanced dynamical evolution. We fitted the radial surface density profile and found that the concentration parameter c > 1, suggesting that the cluster has formed a clear core–halo structure as a result of dynamical evolution. We characterized the mass segregation among the cluster members as well as BSSs using the Minimum Spanning Trees method, indicating a significant central concentration. Additionally, the sedimentation level of the BSSs is measured as , further supporting radial segregation. To probe the BSS formation mechanisms, we estimated their fractional mass excess (M_e), supporting binary mass transfer and mergers as the dominant channels. This is further supported by the presence of six variable BSSs. The dynamical evolution of the cluster is further assessed through its tidal interaction with the Galaxy. Trumpler 19 appears to be within the tidal regime, where strong Galactic tidal forces have a significant influence on the dynamical evolution. This indicates that the cluster may have undergone significant mass-loss processes, potentially leading to its eventual disruption, which is further supported by the orbit analysis of the cluster. We found that Trumpler 19 may have lost more than 95% of its initial mass due to dynamical evolution.

Modified Newtonian dynamics (MOND) has achieved notable success in explaining galaxy-scale phenomena and has made several unexpected, a priori predictions that align with observations. However, MOND struggles to account for the dynamics of galaxy groups and clusters without invoking additional unseen mass. To address these shortcomings, various extensions to MOND have been proposed. Among these, extended MOND (EMOND) and MOND combined with a form of dark matter (DM), denoted MOND + DM, offer distinct theoretical pathways. However, these models often introduce additional degrees of freedom or mathematical complexities that limit their falsifiability. In this work, we investigate the viability of EMOND and MOND + DM in the context of galaxy clusters using both observational and theoretical constraints. We use Chandra observations of cluster temperature profiles, alongside the assumption of hydrostatic equilibrium (HSE), to evaluate the predictive power of these extensions. Our analysis reveals that HSE imposes stringent constraints on MOND-based theories, highlighting points of failure in both the EMOND and MOND + DM paradigms. We derive new theoretical bounds that MOND + DM models must satisfy to remain consistent with observed mass and temperature distributions and show that these can be tested with X-ray observatories such as XRISM. For EMOND, we demonstrate significant inconsistencies between its predictions and observed cluster profiles, suggesting that EMOND is not a viable solution at the cluster scale. Our findings emphasize the need for further theoretical development within the MOND framework to reconcile its success at galaxy scales with its shortcomings in more massive systems.

This paper presents the scenario that gravitational waves, generated in the core collapse of a pre-supernova star, can produce both electromagnetic radiation and sound radiation as gravitational waves propagate outward from the collapsing core. While the energy of this coproduced electromagnetic and sound radiation is orders of magnitude smaller than the initiating gravitational radiation, the power may be sufficient to reignite fusion outside the collapsing core. The nonequilibrium reignition of fusion, in roughly the same time frame as the strongest neutrino emissions, would change the configuration of the pre-supernova star and subsequently the ejecta and the evolution of the stellar expansion of the supernova remnant (SNR). Although the coproduced electromagnetic or sound radiation could not contribute directly to the supernova explosion, the associated nonequilibrium reignition of fusion would alter the state outside the core, leaving an observable signature in the ejecta of the SNR. The aim of this paper is to argue that including this hypothesized coproduced radiation in computational models of core-collapse supernovae would contribute to the evolution of the stellar expansion and consequently should be observable in the SNR, providing a confirmation of the conversion processes for gravitational radiation to electromagnetic and sound radiation.

The interaction between the relativistic jet and the circumburst medium produces a multiwavelength afterglow of a gamma-ray burst (GRBs). In this work, we present multiwavelength properties of GRB 250101A based on the observations of Swift, Fermi, and Mephisto. The spectral analysis of Swift/Swift Burst Alert Telescope (BAT) and Fermi/Gamma-ray Burst Monitor (GBM) reveals a soft prompt spectrum with a low-energy photon index of −1.18 and a peak energy of 33 keV, and the isotropic energy is 1.4 × 10⁵² erg. The prompt emission of GRB 250101A aligns with Type II GRBs in the Amati relation. Meanwhile, our analysis indicates that GRB 250101A is an X-ray-rich or X-ray-dominated GRB, with intrinsic properties suggesting that it is relatively softer than most classical GRBs. Optical observation with Mephisto, beginning 197 s post-trigger, shows a single power-law decay in uvgriz bands, with F_ν,obs ∝ t^−0.76ν^−1.21. The observed spectral index significantly exceeds theoretical predictions under standard afterglow models, suggesting a color excess of ∼0.216 mag. However, combining X-ray and optical afterglow, we find that GRB 250101A is more likely a “normal burst” rather than an “optical-dark burst,” and the dust extinction effect plays an important role in the optical blue bands. Furthermore, there is a structural change at T₀ + 2924 s in the optical light curve, indicating a density drop of ∼50% in the interstellar medium at a distance of ∼0.13 pc. Our analysis shows that this GRB clearly shows some unique characteristics in its observed X-ray-rich prompt emission as well as the circumburst environment, implying a special progenitor.

Millimeter (mm) emission from F-M dwarfs (cool stars) primarily traces chromospheric activity, with thermal emission thought to dominate in quiescence. Despite the high chromospheric activity, the quiescent mm spectral fluence (mm-S(ν)) of young (<1 Gyr) M dwarfs (dMs) remains largely unexplored. We present the quiescent mm-S(ν) of a young dM, AD Leo, observed around 94 GHz using the Northern Extended Millimetre Array. The observed quiescent mm-S(ν) exceeds the thermal flux density from a 1D chromospheric model, constrained by optical-UV spectroscopic data, by up to a factor of 7. This indicates a quasi-steady nonthermal emission powered by suprathermal electrons, unlike in old (>1 Gyr) cool stars, whose quiescent mm-S(ν) generally agree with 1D thermal models. The mm-brightness temperature spectral index (α_mm; T_B(ν)) of AD Leo deviates by a factor of 3 from the α_mm–T_eff scaling law for old Sun-like stars (A. Mohan et al. 2022), while UV Ceti, an older M6V star, follows the trend. Also, we report a double-hump flare with second-scale variability in flux density and spectral index, and a frequency-rising nature with brightness increasing with frequency. The flare resembles certain solar events, but is unlike the second-scale events reported in dMs. The nonthermal flare humps suggest multiple injections of accelerated electrons. The mean flare luminosity (∼2–5 × 10¹⁵ erg s⁻¹ Hz⁻¹) and duration (18 ± 2 s) are comparable to flares reported in AU Mic and Proxima Cen, but 100–1000 times weaker than the minutes-long dM flares observed by the South Pole Telescope.

We report the results of the deepest search to date for dwarf galaxies around NGC 3109, a barred spiral galaxy with a mass similar to that of the Small Magellanic Cloud (SMC), using a semiautomated search method. Using the Dark Energy Camera, we survey a region covering a projected distance of ∼70 kpc of NGC 3109 (D = 1.3 Mpc, R_vir ∼ 90 kpc, M ∼ 10⁸M_*) as part of the MADCASH and DELVE-DEEP programs. We introduce a newly developed semiresolved search method, used alongside a resolved search, to identify crowded dwarf galaxies around NGC 3109. Using both approaches, we successfully recover the known satellites Antlia and Antlia B. We identified a promising candidate, which was later confirmed to be a background dwarf through deep follow-up observations. Our detection limits are well defined, with the sample ∼80% complete down to M_V ∼ −8.0, and include detections of dwarf galaxies as faint as M_V ∼ −6.0. This is the first comprehensive study of a satellite system through resolved stars around an SMC mass host. Our results show that NGC 3109 has more bright (M_V ∼ −9.0) satellites than the mean predictions from cold dark matter models, but well within the host-to-host scatter. A larger sample of LMC/SMC-mass hosts is needed to test whether or not the observations are consistent with current model expectations.

Star cluster formation and assembly occur inside filamentary and turbulent molecular clouds, which imprint both spatial and kinematic substructure on the young cluster. In this paper, we quantify the amount and evolution of this substructure in simulations of star cluster formation that include radiation magnetohydrodynamical evolution of the gas, coupled with detailed stellar dynamics, binary formation and evolution, and stellar feedback. We find that both spatial and kinematic substructure are present at early times. Both are erased as the cluster assembles through the formation of new stars as well as the merger of subclusters. Spatial substructure is erased over a timescale of approximately 2.5 times the initial freefall time of the cloud. Kinematic substructure persists for longer and is still present to the end of our simulations. We also explored our simulations for evidence of early dynamical mass segregation and concluded that the presence of a population of binary stars can accelerate and enhance the mass segregation process.

We study the spectral evolution of the Z-track source GX 17+2 using AstroSat and NICER observations taken between 2016 and 2020. The AstroSat observations cover the period when the source is in the normal branch (NB) and the flaring branch (FB), while for the NICER ones the variability can be associated with the FB branch. The source spectra at different regions of the branches are well described by accretion disk emission, blackbody surface emission, and a thermal Comptonization component. In the NB, the total bolometric unabsorbed flux remains constant and the variation is due to changes in the Comptonization, disk fluxes. In particular, the inferred luminosity (L_T) and accretion rate () remain constant, while there is significant variation in the inner disk radii and fraction of disk photons entering the corona, indicating changes in the geometry of the system. On the other hand, in the FB, there is significant variation in luminosity from ∼4.0 to ∼7.0 × 10³⁸ erg s⁻¹. Despite this significant variation in luminosity and in the inner disk radii, the accretion efficiency, defined as , remains nearly constant at ∼0.20 throughout the evolution of the source, as expected for a neutron star system.

We present a catalog of 8545 and 19,257 unique DA white dwarfs (WDs) observed in Sloan Digital Sky Survey (SDSS) Data Release 19 and previous SDSS data releases, respectively. This is the largest catalog of both spectroscopic and photometric measurements of DA WDs available to date, and we make this catalog and all codes used to create it publicly available. We measure the apparent radial velocity, spectroscopic effective temperature and surface gravity, and photometric effective temperature and radius for all objects in our catalog. We validate our measurements against other published WD catalogs. For apparent radial velocities, surface gravities, and effective temperatures measured from spectra with signal-to-noise ratios >​ ​​​​​​50, our measurements agree with published SDSS WD catalogs to within 7.5 km s⁻¹, 0.060 dex, and 2.4%, respectively. For radii and effective temperatures measured with Gaia photometry, our measurements agree with other published Gaia data sets to within 0.0005 R_⊙ and 3%, respectively. We use this catalog to investigate systematic discrepancies between WDs observed in SDSS-V and previous generations of SDSS. For objects observed in both SDSS-V and previous generations, we uncover systematic differences between measured spectroscopic parameters depending on which set of survey data is used. On average, the measured apparent radial velocity of a DA WD is 11.5 km s⁻¹ larger, and the surface gravity is 0.015 dex smaller when a WD’s spectroscopic parameters are measured using SDSS-V data compared to using data from previous generations of SDSS. These differences may be due to changes in the wavelength solution across survey generations.

Using a large sample of 9617 molecular clouds (MCs) from the Milky Way Imaging Scroll Painting survey, we mainly measure one-dimensional cloud-to-cloud velocity dispersions across a 450 deg² segment of the Local Arm in the Galactic second quadrant. We define the cloud-to-cloud velocity dispersion using two metrics: the standard deviation (σ_bin) and flux-weighted rms value (σ_bin,w) of the centroid velocities of ¹²CO-detected MCs within spatial bins. The typical values of σ_bin and σ_bin,w are 7.5 ± 0.5 km s⁻¹ and 6.2 ± 0.5 km s⁻¹, respectively. After categorizing clouds by sizes into three types: Type S (0.15–1.2 pc), Type M (1.2–4.8 pc), and Type L (≳4.8 pc), we find that the spatial distribution of Type S and M MCs projected onto the Galactic longitude–latitude (l–b) plane is generally uniform. Additionally, the cloud-to-cloud velocity dispersion among Type S clouds (∼7.6 and 7.4 km s⁻¹ for σ_bin and σ_bin,w, respectively) is systematically greater than that among Type M clouds (∼6.7 and 6.0 km s⁻¹ for σ_bin and σ_bin,w, respectively), with differences of 0.9–1.4 km s⁻¹. From these measurements, we estimate merger timescales between MCs to be approximately 0.3–0.9 Myr, which is shorter than their internal crossing timescales (∼1 Myr for Type S, ∼2 Myr for Type M, and ≳5 Myr for Type L). This disparity, particularly pronounced for larger Type L clouds, suggests that MCs are dynamically transient structures, with their gas content changing due to frequent interactions with neighboring clouds.

Low-m inertial modes have been recently discovered in the Sun’s high-latitude regions. In this study, we characterize the observational properties of the m = 1 mode by analyzing time–distance subsurface flow maps. Synoptic flow maps, constructed from daily subsurface flow maps using a tracking rate corresponding to the rotation at latitude 65°, are filtered in both the spherical harmonic and Fourier domains to retain only the m = 1 mode and its dominant frequencies. Our analysis reveals a power distribution that is significantly stronger in the northern polar region. The mode’s power exhibits an anticorrelation with solar activity, remaining strong and persistent during the solar activity minimum and becoming weaker and more fragmented during the solar maximum. Magnetic flux transported from low to high latitudes influences both the mode’s power and lifetime, enhancing its power and shortening its lifetime upon arrival. The phases of the m = 1 mode in the northern and southern polar regions are near-antisymmetric for most of the time with short deviations. We also compute zonal and meridional phase velocities of the mode and find that it exhibits significantly less differential rotation than its surrounding plasma. The meridional phase velocity, comprising both the local plasma’s meridional flow and the mode’s intrinsic phase motion, is directed poleward below latitude 70° and equatorward above this latitude. These observational findings underscore the need for a deeper understanding of the internal dynamics of the low-m modes, which may offer valuable insights into the structure and dynamics of the solar interior.

A range of stellar explosions, including supernovae (SNe), tidal disruption events (TDE), and fast blue optical transients (FBOTs), can occur in dusty environments initially opaque to transients’ optical/UV light, becoming visible only once the dust is destroyed by transients’ rising luminosity. We present axisymmetric, time-dependent radiation transport simulations of dust-shrouded transients with Athena++ and tabulated gray opacities, predicting the light curves of the dust-reprocessed infrared (IR) radiation. The luminosity and timescale of the IR light curve depend on whether the transient rises rapidly or slowly compared to the light-crossing time of the photosphere, t_lc. For slow-rising transients (t_rise  ≫  t_lc) like SNe, the reprocessed IR radiation diffuses outward through the dust shell faster than the shell sublimates; the IR light curve therefore begins rising prior to the escape of UV/optical light, but peaks on a timescale ∼t_rise shorter than the transient duration. By contrast, for fast-rising transients (t_rise  ≪  t_lc) such as FBOTs and some TDEs, the finite light-travel time results in the reprocessed radiation arriving as an “echo” lasting much longer than the transient itself. We explore the effects of the system geometry by considering a torus-shaped distribution of dust. The IR light curves seen by observers in the equatorial plane of the torus resemble those for a spherical dust shell, while polar observers see faster-rising, brighter, and shorter-lived emission. We successfully model the IR excess seen in AT2018cow as a dust echo, supporting the presence of an opaque dusty medium surrounding FBOTs prior to explosion.

We present a novel python-based 1D sub-Neptune evolution model that emphasizes the thermal evolution and potential solidification of the rock/iron core and the structure of the radiative atmosphere. This model explores planetary structure from the molten center to nbar pressure levels. Treating the radiative atmosphere is crucial for sub-Neptunes, due to the large scale height and low gravity, which contributes up to 40% of their observed radius, especially for low-mass, highly irradiated planets. Consequently, we generically find that lower H/He mass fractions are needed to match a given planetary radius, compared to previous work. While the presence of metal enrichment in the H/He layers (here modeled as 50× solar) does not substantially influence the size of the convective envelope, it notably reduces the transit radius by shrinking the radiative atmospheric scale height. Sub-Neptunes cool differently from terrestrial planets, with the rock/iron core’s cooling rate limited by the envelope, leading to longer solidification timescales. Complete solidification of the silicate mantle by 10 Gyr is found only for planets with very low masses (≤1M_⊕) and small H/He envelopes (≤0.1%). Dynamo action in sub-Neptune iron cores persists as long as the mantle surface remains molten, often exceeding 10 Gyr, and becomes sensitive to core thermal conductivity after solidification. We examine aspects of “boil-off,” which sets the maximum allowed H/He mass and planetary radius for subsequent evolution. The rock/iron’s cooling energy moderately decreases the post-boil-off H/He mass fraction in planets with large atmospheric scale heights only.

We present initial results from the 4.8 GHz Very Long Baseline Array (VLBA) survey of the JWST North Ecliptic Pole Time-Domain Field (TDF). From 106 radio sources found in the Karl G. Jansky Very Large Array (VLA) observations in the TDF, we detected 12 sources (∼11% detection rate) at ∼3.3 μJy rms sensitivity and ∼4 mas resolution. Most detections exhibit parsec-scale emission (less than 40 pc) with high VLBA/VLA flux density ratios and brightness temperatures exceeding 10⁵ K, confirming nonthermal active galactic nucleus (AGN) activity. Spectral indices α ≳ −0.5 correlate with higher VLBA/VLA flux ratios, consistent with synchrotron emission from AGN coronae or jets. In the majority of our sources, star formation contributes less than 50% of the total VLBA radio emission, with a few cases where the emission is almost entirely AGN driven. Although the radio emission from radio quiet AGN is thought to be primarily driven by star formation, our VLBA observations confirm that there is also often a contribution at various levels from black hole driven AGN. Eight VLBA detections have JWST/NIRCam counterparts, predominantly early-type, bulge-dominated galaxies, which we use to get an estimate of the redshift and star formation rate (SFR). Wide-field Infrared Survey Explorer colors indicate that VLBA detections are either AGN or intermediate-disk-dominated systems, while VLBA nondetections correspond to extended, star-forming galaxies. We compare SFRs derived from previous SCUBA-2 850 μm observations with new JWST-based estimates, and discuss the observed discrepancies, highlighting JWST’s improved capability to disentangle AGN activity from star formation.

We report the serendipitous detection of the SO J_N = 6₅–5₄ (219.949 GHz) rotational transition in archival Atacama Large Millimeter/submillimeter Array observations of the spiral hosting protoplanetary disks around CQ Tau (with ≈4.9σ significance) and MWC 758 (with ≈3.4σ significance). In the former, the SO emission comes in the shape of a ring, arises from the edge of the continuum cavity, and is qualitatively consistent, at the currently available spectral resolution, with being in Keplerian rotation. In the latter, instead, while arising primarily from inside the continuum cavity, the SO emission also extends to the continuum ring(s), and its morphology and kinematics are less clear. We put these sources in the context of the other protoplanetary disks where SO detections have been previously reported in the literature and discuss the possible origins of SO in terms of (thermal) desorption or formation in the gas-phase. We argue that these processes might be fostered by dynamical perturbations caused by unseen embedded massive companions, shadows, or late-time infall, thus suggesting a possible link between perturbed dynamics and SO emission in (these) protoplanetary disks. If confirmed, our interpretation would imply that chemical evolution timescales could be significantly shorter in these systems than is commonly assumed, indicating that dynamical perturbations might influence the composition of newborn (proto)planets by altering the volatile makeup of their formation environment.

We present spectroscopic Lyα luminosity functions (LFs) at z = 5.7 and z = 6.6 based on a large 209 source sample of Lyα emitter (LAE) candidates identified in Subaru/Hyper Suprime-Cam narrowband imaging and confirmed with Keck II/DEIMOS spectroscopy over a multiyear observing campaign. After applying photometric and spectroscopic cuts to produce homogeneous samples, we use the resulting samples of 49 z = 5.7 and 56 z = 6.6 LAEs to compute spectroscopic LAE LFs at each redshift. We correct our LFs for incompleteness using a source-injection simulation. We find excellent agreement with current spectroscopic and photometric LAE LFs from the literature. We look for evolution over the redshift range z = 5.7–6.6. We find a strong convergence of the LFs at L_Lyα ≳ 10^43.4 erg s⁻¹. This convergence (noted in previous literature) provides strong evidence that the most luminous LAEs at z = 6.6 form ionized bubbles around themselves, allowing for greater Lyα transmission through the neutral intergalactic medium, which is measured as an increase in the bright end of the z = 6.6 LF over the expected evolution in the LF based on the faint end. We infer that ultraluminous LAEs may play a significant role in reionization.

We present a structural analysis of 138 compact elliptical galaxies (cEs) in the redshift range of z < 0.05 using the Sloan Digital Sky Survey (SDSS) DR12 data. We perform single- and double-component Sérsic model fitting to their SDSS r-band surface brightness profiles. By dividing cEs into those with [cE(w)] and without [cE(w/o)] a bright host galaxy, we find a significant structural dichotomy: the majority (∼85%) of cE(w)s exhibit single-component profiles, while a similar proportion (∼85%) of isolated cE(w/o)s display double-component profiles, characterized by a compact, inner component and a diffuse, disk-like outer component. These results suggest that host-associated cE(w)s primarily form through the tidal stripping of larger progenitors, resulting in a compact bulge-like core. In contrast, isolated cE(w/o)s appear to form intrinsically at early epochs, likely through gas-rich mergers, and retain disk-like outer structures. The Sérsic index distribution of cE(w)s with single-component structure indicates progenitor types ranging from pseudobulge to classical bulge, supported by differences in stellar populations. A small fraction of cEs, including double-component cE(w)s and single-component cE(w/o)s, suggests complex evolutionary channels involving environmental capture or ejection. Our results emphasize that the structural characteristics of cEs, specifically the presence or absence of an extended outer envelope, serve as a crucial diagnostic tool to distinguish tidally stripped remnants from intrinsically formed low-mass cEs in isolation.

The quasi-instantaneous emission from a relativistic surface endowed with a Lorentz factor that decreases away from the outflow symmetry axis can naturally explain the three phases observed by Swift X-Ray Telescope (XRT) in gamma-ray bursts (GRBs) and their afterglows (GRB tail, afterglow plateau, and postplateau) based only on the angular change of the relativistic Doppler boost across the outflow surface. We develop further the analytical formalism of the “larger-angle emission” model for the case of “n-exponential” outflows (where the Lorentz factor Γ dependence of the angular location θ is ), and compare its ability to account for the X-ray emission of XRT afterglows relative to that of “power-law” outflows (Γ ∼ θ^−g). Power-law outflows yield longer afterglow plateaus, followed by slower postplateau flux decays than n-exponential outflows, features which may be used in identifying which type of angular structure is at work in a given afterglow. Identifying the Γ(θ) angular structure that accommodates XRT light curves is slightly complicated by the fact that the afterglow X-ray light curve is also determined by how two characteristics of the comoving-frame emission spectrum (peak energy and peak intensity ) change with the angular location or, equivalently, with the Lorentz factor. Here, we assume power-law Γ dependences of those spectral characteristics and find that, unlike power-law outflows, n-exponential outflows cannot account for plateaus with a temporal dynamical range larger than 100 (2 dex in logarithmic space). To capture all the information contained in XRT afterglow measurements (0.3–10 keV unabsorbed flux and effective spectral slope), we calculate 0.3 and 10 keV light curves using a broken-power-law emission spectrum of peak energy and low- and high-energy slopes that are derived from the effective slope measured by XRT. This economical peak energy determination is found to be consistent with the results of more expensive spectral fits. The angular distributions of the Lorentz factor, comoving frame peak energy, and peak intensity () constrain the (yet-to-be determined) convolution of various features of the production of relativistic jets by solar-mass black holes and of their propagation through the progenitor/circumburst medium, while the and dependences may constrain the GRB dissipation mechanism and the GRB emission process.

Many past studies have predicted the steady-state production and maintenance of abiotic O₂ and O₃ in the atmospheres of CO₂-rich terrestrial planets orbiting M dwarf stars. However, the time-dependent responses of these planetary atmospheres to flare events—and the possible temporary production or enhancement of false-positive biosignatures therein—has been comparatively less well studied. Most past works that have modeled the photochemical response to flares have assumed abundant free oxygen, like that of the modern or Proterozoic Earth. Here we examine in detail the photochemical impact of the UV emitted by a single flare on abiotic O₂/O₃ production in prebiotic, CO₂-dominated atmospheres of M dwarf planets with CO₂ levels ranging from 3% to 80% of 1 bar. We find that a single flare generally destroys O₂ and O₃ over short timescales while modestly enhancing their column densities over intermediate timescales. We simulate the spectral observables of both the steady-state atmosphere and time-dependent spectral response over the flare window for both emitted and transmitted light spectra. Over the course of the flare, the O₃ UV Hartley band is decreased by a maximum of 47 ppm. In both emitted and transmitted light spectra, the 9.65 μm O₃ band is hidden by the overlapping 9.4 μm CO₂ band for all scenarios considered. Overall, we find that the possible enhancements of abiotic O₃ due to a single flare are small compared to O₃’s sensitivity to other parameters such as CO₂ and H₂O abundances or the availability of reducing gases such as H₂.

At high eccentricities, tidal forcing excites vibrational modes within orbiting bodies known as dynamical tides. In this paper, we implement the coupled evolution of these modes with the body’s orbit in the REBOUNDx framework, an extension to the popular N-body integrator REBOUND. We provide a variety of test cases relevant to exoplanet dynamics and demonstrate overall agreement with prior studies of dynamical tides in the secular regime. Our implementation is readily applied to various high-eccentricity scenarios and allows for fast and accurate N-body investigations of astrophysical systems for which dynamical tides are relevant.

Giant radio sources, including galaxies and quasars (hereafter GRSs), are active galactic nuclei (AGN) hosting relativistic jets with source sizes exceeding a projected length of 0.7 Mpc. They are crucial to understanding the evolution of radio sources and their interaction with the surrounding environment. Some of these enigmatic objects, e.g., NGC 315, have also been reported as γ-ray emitters. Since GRSs are thought to be aligned close to the plane of the sky, they are invaluable targets to explore the radiative mechanisms responsible for the observed γ-ray emission. We have carried out a systematic search of γ-ray-emitting GRSs using sensitive low-resolution radio surveys, such as by the Low Frequency Array, NRAO Very Large Array Sky Survey, and Rapid ASKAP Continuum Survey, and considering the fourth data release of the fourth Fermi Large Area Telescope γ-ray source (4FGL-DR4) catalog. By carefully inspecting the radio maps of all AGN included in the 4FGL-DR4 catalog, we have identified 16 γ-ray-emitting GRSs, including eight that are being reported as GRSs for the first time. Some of their observed parameters, e.g., core dominance, appeared to differ from those found for the non-γ-ray detected GRS population, possibly due to the relatively small viewing angle of the γ-ray-emitting jet. The observed γ-ray properties of these objects were found to be similar to those of non-GRS γ-ray-emitting misaligned AGN. We conclude that the origin of the γ-ray emission could be similar in both source populations.

Relativistic pair beams created in the intergalactic medium (IGM) by TeV gamma rays from blazars are expected to produce a detectable GeV-scale electromagnetic cascade, but the cascade component is absent in the spectra of many hard-spectrum TeV-emitting blazars. One common explanation is that weak intergalactic magnetic fields deflect the electron–positron pairs away from our line of sight. An alternative possibility is that electrostatic beam-plasma instabilities drain the energy of these pairs before a cascade can develop. Recent studies have shown that beam scattering by oblique electrostatic modes leads to minimal energy loss. But these modes might be suppressed by linear Landau damping (LLD) due to MeV-scale cosmic-ray electrons in the IGM. In this work, we explore the impact of LLD on the energy-loss efficiency of plasma instabilities in pair beams associated with 1ES 0229+200. We find that LLD effectively suppresses oblique electrostatic modes, while quasi-parallel ones grow to larger amplitudes. In this way, LLD enhances the energy-loss efficiency of the instability by more than an order of magnitude.

Measurements of the GD-1 star stream velocity distribution within ±3° of the centerline find a total line-of-sight velocity spread of 5–6 km s⁻¹ in the-well measured ϕ₁ = [−30, 0] region. The velocity spread is far above the ∼2–3 km s⁻¹ of a dissolved globular cluster in a smooth galactic potential. Dynamical heating of the GD-1 star stream is simulated in an evolving model Milky Way potential that includes the subhalos extracted from cosmological cold dark matter (CDM) and warm dark matter (WDM) Milky Way–like halos. The model bridges fully cosmological Milky Way–like halos and late-time static Milky Way potentials, allowing individual streams to be accurately integrated. An evolving CDM subhalo population acting for ∼11 Gyr heats GD-1 to 6.2  ±  1.7 km s⁻¹. The WDM (7 keV and lighter) models develop a velocity dispersion of 3.9  ±  0.2 km s⁻¹, only slightly greater than the 3.5 km s⁻¹ in an evolving smooth halo without subhalos for 11 Gyr. The dynamical age of the best model stream is close to the isochrone age of the stars in the stream. Subhalos with masses in the decade around 10^7.5M_⊙, below the mass range of dwarf galaxies, dominate the dynamical stream heating.

Spicules are thin, elongated, jet-like features seen in observations of the solar atmosphere, at the interface between the solar photosphere and the corona. These features exhibit highly complex dynamics and are a necessary connecting link between the cooler, denser solar chromosphere and the extremely hot, tenuous corona. In this work, we explore the spatial and temporal relation between solar spicules and magnetohydrodynamic (MHD) shocks using data from a 2D radiative MHD simulation of the solar atmosphere driven by solar convection. Here, we demonstrate, through direct identification, that slow MHD shocks, which propagate along magnetic field lines, are regions of strong positive vertical acceleration of the plasma that forms the tip of the spicule material during its rise phase. We quantify the effect of pressure and Lorentz forces on the acceleration of the plasma inside the shocks during the rise of spicules. The causality between spicule and shock propagation in the atmosphere of the model is also investigated. It is further shown that the strength of these shocks may play a vital role in determining the height of the spicules, supporting the idea that shocks act as drivers of some spicules. In addition, we also find the presence of structures similar to propagating coronal disturbances (PCDs) in the simulation, linked with the spicules. Here, PCDs appear to be associated with the shock waves driving the spicules that subsequently propagate into the corona and have similar speeds to those reported in observations.

We present polarization images from the Karl G. Jansky Very Large Array and the Giant Metrewave Radio Telescope at 5.5 GHz, 10 GHz, and 663 MHz of the changing-look active galactic nuclei, NGC 3516. A transverse gradient in the rotation measure (RM) is detected in the northern and southern kiloparsec-scale lobes. Such gradients have typically been suggested to be signatures of a helical magnetic (B-) field. We detect circular polarization in the core and inner jet-knot of this source, which is known to host a precessing radio jet interacting with emission-line gas. Soft X-ray emission from the Chandra X-ray Observatory suggests the presence of a hot wind emerging from the nucleus of NGC 3516. Taken together with the RM gradient, this presents a picture of jet+wind outflow in this Seyfert galaxy with the B-field confining both the jet and lobe emission. A magnetically driven outflow may, in turn, cause accretion disk warping and jet precession, which is observed in the case of NGC 3516.

While stellar jets and outflows are fueled by accretion from disks, their direct influence on disks remain unexplored. Here, we revisit Atacama Large Millimeter/submillimeter Array observations of ¹²CO (J = 2–1) line emission for the young stellar object WSB 52. We identify an expanding bubble that interacts with its protoplanetary disk. Given that the disk axis points toward the bubble’s center and the kinetic energy of the bubble is roughly 10⁴¹ erg, we postulate that stellar jets, aligned with the disk axis, have triggered the bubble. The bubble morphology is consistent with uniform expansion with partial concavity, implying the bubble-disk interaction. Correspondingly, the shape and the velocity field of protoplanetary disk appear to be deformed and exhibit high-velocity components, suggesting strong interactions and mass loss from the disk. The discovery of jet feedback onto the disk via the bubble—which we term the jet-bubble-diskjet–bubble–disk interaction—sheds new light on the dynamical processes governing star and planet formation.

We propose a new framework for the simultaneous feedback of stellar winds and photoionizing radiation from massive stars, distinguishing the locations where forces are applied, and consequences for internal spatiotemporal evolution of the whole feedback bubble (FB). We quantify the relative dynamical importance of wind-blown bubbles (WBBs) versus the photoionized region (PIR) by the ratio of the radius at which the WBB is in pressure equilibrium with the PIR, R_eq, to the Strömgren radius, R_St. ζ ≡ R_eq/R_St quantifies the dynamical dominance of WBBs (ζ > 1) or the PIR (ζ < 1). We calculate ζ and find that, for momentum-driven winds, 0.1 ≲ ζ ≲ 1 for the star-forming regions in (i) typical Milky Way–like giant molecular clouds, (ii) the most massive of individual OB stars, and (iii) dense, low-metallicity environments, relevant in the early Universe. In this regime, both WBBs and the PIR are dynamically important to the expansion of the FB. We develop a semianalytic coevolution model (CEM) that takes into account the spatial distribution of forces and the back reactions of both the WBB and PIR. In the ζ < 1 regime where the CEM is most relevant, the model differs in the total FB momentum by up to 25% compared to naive predictions. In the weak-wind limit of ζ ≪ 1, applicable to individual OB stars or low-mass clusters, the CEM has factors ≳2 differences in WBB properties. In a companion paper, we compare these models to 3D, turbulent hydrodynamical simulations.

In a companion paper (Paper I), we presented a coevolution model (CEM) in which to consider the evolution of feedback bubbles driven by massive stars through both stellar winds and ionizing radiation, outlining when either of these effects is dominant and providing a model for how they evolve together. Here we present results from 3D radiation magnetohydrodynamical simulations of this scenario for parameters typical of massive star-forming clouds in the Milky Way: precisely the regime where we expect both feedback mechanisms to matter. While we find that the CEM agrees with the simulations to within 25% for key parameters and modestly outperforms previous idealized models, disagreements remain. We show that these deviations originate mainly from the CEM’s lack of (i) background inhomogeneity caused by turbulence and (ii) time-variable momentum enhancements in the wind-blown bubble (WBB). Additionally, we find that photoionized gas acts similarly to magnetic fields by decreasing the WBB’s surface area. This causes a decrease in the amount of cooling at the WBB’s interface, resulting in an enhanced WBB dynamical impact.

Studying the radio spectral energy distribution (SED) of distant galaxies is essential for understanding their assembly and evolution over cosmic time. We present rest-frame radio SEDs of a sample of 160 star-forming galaxies at 1.5 < z < 3.5 in the Cosmic Evolution Survey field as part of the MeerKAT International GHz Tiered Extragalactic Exploration project. MeerKAT observations combined with archival Very Large Array and Giant Metrewave Radio Telescope data allow us to determine the integrated mid-radio (ν = 1–10 GHz) continuum (MRC) luminosity and magnetic field strength. A Bayesian method is used to model the SEDs and to separate the free–free and synchrotron emission. We also calibrate the star formation rate (SFR) in radio both directly through SED analysis and indirectly through the infrared–radio correlation (IRRC). With a mean value of α_nt ≃ 0.7, the synchrotron spectral index flattens with both redshift and specific SFR, indicating that cosmic rays are more energetic in the early Universe due to higher star formation activity. The magnetic field strength increases with redshift, B ∝ (1 + z)^(0.7±0.1), and SFR as B ∝ SFR^0.3, suggesting a small-scale dynamo acting as its main amplification mechanism. Taking into account the evolution of the SEDs, the IRRC is redshift invariant, and it does not change with stellar mass at 1.5 < z < 3.5, although the correlation deviates from linearity. Similarly, we show that the SFR traced using the integrated MRC luminosity is redshift invariant.

Ion cyclotron waves (ICWs) are ubiquitous phenomena within Saturn’s magnetosphere, particularly in the vicinity of Enceladus. This study focuses on the Cassini spacecraft’s flyby data of Enceladus to investigate the spatial distribution and properties of ICWs. We categorize ICWs into two distinct types based on their frequency characteristics: Type I, with frequencies deviating from the local ion cyclotron trend, detected during high-inclination flybys; and Type II, with frequencies closely following the local trend, observed during horizontal flybys. Moreover, we identify the simultaneous detection of ICWs and magnetosonic waves within Saturn’s magnetosphere, providing new insights into their generation and propagation mechanisms. Our results show that ICWs serve as crucial diagnostic tools for evaluating local plasma conditions and the dynamics of Saturn’s magnetosphere. Furthermore, this study highlights the broader implications of ICWs for comparative planetary magnetospheric research, providing guidance for investigating similar processes at other planetary systems, such as Jupiter’s moons Io and Europa.

Detecting the first generation of stars, Population III (Pop III), has been a long-standing goal in astrophysics, yet they remain elusive even in the JWST era. Here we present a novel NIRCam-based selection method for Pop III galaxies, and carefully validate it through completeness and contamination simulations. We systematically search ≃ 500 arcmin² across JWST legacy fields for Pop III candidates, including GLIMPSE, which, assisted by gravitational lensing, has produced JWST’s deepest NIRCam imaging thus far. We discover one promising Pop III galaxy candidate (GLIMPSE-16043) at , a moderately lensed galaxy () with an intrinsic UV magnitude of . It exhibits key Pop III features: strong Hα emission (rest-frame EW 2810 ± 550 Å); a Balmer jump; no dust (UV slope β = −2.34 ± 0.36); and undetectable metal lines (e.g., [O iii]; [O iii]/Hβ < 0.44), implying a gas-phase metallicity of Z_gas/Z_⊙ < 0.5%. These properties indicate the presence of a nascent, metal-deficient young stellar population (<5 Myr) with a stellar mass of ≃10⁵M_⊙. Intriguingly, this source deviates significantly from the extrapolated UV–metallicity relation derived from recent JWST observations at z = 4–10, consistent with UV enhancement by a top-heavy Pop III initial mass function or the presence of an extremely metal-poor active galactic nucleus. We also derive the first observational constraints on the Pop III UV luminosity function at z ≃ 6–7. The volume density of GLIMPSE-16043 (≈10⁻⁴ cMpc⁻³) is in excellent agreement with theoretical predictions, independently reinforcing its plausibility. This study demonstrates the power of our novel NIRCam method to finally reveal distant galaxies even more pristine than the Milky Way’s most metal-poor satellites, thereby promising to bring us closer to the first generation of stars than we have ever been before.

The standard cosmological model with cold dark matter posits a hierarchical formation of structures. We introduce topological neural networks (TNNs), implemented as message-passing neural networks on higher-order structures, to effectively capture the topological information inherent in these hierarchies that traditional graph neural networks (GNNs) fail to account for. Our approach not only considers the vertices and edges that comprise a graph but also extends to higher-order cells such as tetrahedra, clusters, and hyperedges. This enables message-passing between these heterogeneous structures within a combinatorial complex. Furthermore, our TNNs are designed to conserve the E(3) invariance, which refers to the symmetry arising from invariance against translations, reflections, and rotations. When applied to the Quijote suite, our TNNs achieve a significant reduction in the mean squared error. Compared to our GNNs, which lack higher-order message-passing, ClusterTNNs show improvements of up to 22% in Ω_m and 34% in σ₈ jointly, while the best FullTNN achieves an improvement of up to 60% in σ₈. In the context of the CAMELS suite, our models yield results comparable to the current GNN benchmark, albeit with a slight decrease in performance. We emphasize that our topology and symmetry-aware neural networks provide enhanced expressive power in modeling the large-scale structures of our Universe.

We investigate the chemical abundance distributions of the Fornax, Sculptor, Ursa Minor, and Draco dwarf galaxies using Subaru/Hyper Suprime-Cam (HSC) photometric data. The HSC data set, which includes broadband g and i filters and the narrowband NB515 filter, offers sensitivity to iron and magnesium abundances, as well as surface gravity, enabling the identification of giant stars and foreground dwarfs. For analysis, we selected a total of 6713 giant candidates using a random forest regressor trained on medium-resolution (R ∼ 6000) Keck/Deep Imaging Multi-Object Spectrograph spectroscopic data. Our analysis reveals the extent of radial metallicity gradients in the galaxies. Such trends, not detectable in earlier studies, are now captured owing to the substantially enlarged sample size and areal coverage provided by the HSC data. These results are also consistent with chemical abundance patterns previously observed in the central regions through spectroscopic studies. Furthermore, we infer that Fornax underwent extended star formation, whereas Sculptor formed both metal-poor and metal-rich stars over a shorter time. Ursa Minor and Draco appear to have experienced brief, intense star formation episodes leading to nearly extinguished star formation. This study underscores the critical role of the expanded HSC data set in revealing chemical gradients that were previously inaccessible. Future work incorporating additional spectra of metal-poor stars and age-sensitive isochrone modeling will enable more accurate maps of chemical abundance distributions.

We present a comprehensive analysis of the extended emission-line region (EELR) in the host galaxy of the tidal disruption event (TDE) AT2019qiz, utilizing Very Large Telescope (VLT)/MUSE integral-field spectroscopy. The high spatial-resolution data reveal a biconical emission structure approximately 3.7 kpc in scale within the galactic center, characterized by a prominent [O iii] line in the nucleus and significant [N ii] line emission extending into the EELR. Spectral analysis of the EELR indicates line ratios consistent with Seyfert ionization in the center and LINER-type ionization in the outer diffuse region, suggesting ionization from galactic nuclear activity. The required ionizing luminosity, estimated from the Hα and Hβ luminosities based on the photoionization and recombination balance assumption, is 10^41.8 erg s⁻¹ for all spaxels classified as active galactic nucleus (AGN), and 10^40.7 erg s⁻¹ for spaxels in the central 0.9 kpc Seyfert region. However, the current bolometric luminosity of the nucleus L_bol ≤ 10^40.8 erg s⁻¹, estimated from quiescent-state soft X-ray observations, is insufficient to ionize the entire EELR, implying a recently faded AGN or a delayed response to historical activity. Stellar population analysis reveals a poststarburst characteristic in the EELR, and the gas kinematics show disturbances and noncircular components compared to the stellar kinematics. Notably, the recent detection of quasiperiodic eruptions (QPEs) in the X-ray light curve of AT2019qiz confirms the TDE–QPE association. Our findings provide direct evidence for an AGN-like EELR in the host galaxy of the nearest TDE with QPE detection, offering new insights into the complex interplay between TDEs, QPEs, AGN activity, and host-galaxy evolution.

The advent of JWST has marked a new era in exoplanetary atmospheric studies, offering higher-resolution data and greater precision across a broader spectral range than previous space-based telescopes. Accurate analysis of these data sets requires advanced retrieval frameworks capable of navigating complex parameter spaces. We present NEXOTRANS, an atmospheric retrieval framework that integrates Bayesian inference using UltraNest/PyMultiNest with four machine learning algorithms: Random Forest, Gradient Boosting, K-Nearest Neighbor, and Stacking Regressor. This hybrid approach enables a comparison between traditional Bayesian methods and computationally efficient machine learning techniques. Additionally, NEXOTRANS incorporates NEXOCHEM, a module for solving equilibrium chemistry. We applied NEXOTRANS to JWST observations of the Saturn-mass exoplanet WASP-39 b, spanning wavelengths from 0.6 to 12.0 μm using NIRISS, NIRSpec PRISM, and MIRI. Four chemistry models—free, equilibrium, modified hybrid equilibrium, and modified equilibrium-offset chemistry—were explored to retrieve precise volume mixing ratios (VMRs) for H₂O, CO₂, CO, H₂S, and SO₂. Absorption features in both NIRSpec PRISM and MIRI data constrained SO₂ log VMRs to values between −6.25 and −5.73 for all models except equilibrium chemistry. High-altitude aerosols, including ZnS and MgSiO₃, were inferred, with constraints on their VMRs, particle sizes, and terminator coverage fractions, providing insights into cloud composition. For the best-fit modified hybrid equilibrium model, we derived supersolar elemental abundances of solar, solar, and solar, along with a C/O ratio of solar. These results demonstrate NEXOTRANS’s potential to enhance JWST data interpretation, advancing comparative exoplanetology efficiently.

Using both analytical and numerical means, we demonstrate that linear stability analysis of a hydrodynamic stratified atmosphere or a 1D coronal loop model in nonadiabatic settings features a thermal continuum corresponding to highly localized eigenfunctions. This thermal continuum can be precomputed, involving the net heat-loss function and its partial derivatives, and is the generalization of the thermal instability introduced by E. N. Parker. We account for a thermal imbalance, directly affecting thermal instability growth rates. We present completely general equations that govern all eigenmodes, including nonadiabatically affected p- and g-modes of the stratified settings. We intend to clarify how linear thermal instability is relevant for solar loops that show spontaneous in situ condensations, and eliminate recent confusion on specific isochoric routes to linear instability alongside other thermal instability channels. The thermal continuum, previously identified as a crucial ingredient in magnetohydrodynamic eigenmode spectra for coronal loops and atmospheres, drives multithermal aspects across our Universe, such as forming solar coronal rain and prominences, or cold cloud creation in intracluster to interstellar medium environments.

We present high-resolution Karl G. Jansky Very Large Array observations of the 22 GHz H₂O maser line in the extended Sagittarius B2 cloud. We detect 499 H₂O masers across the observed velocities between −39 and 172 km s⁻¹. To investigate the nature of the masers, we analyze their spatial distribution and crossmatch with catalogs of H II regions and protostellar cores. 62% of masers are associated with protostellar cores and 32% with H II regions. The nature of the remaining 6% of sources was not established but is likely associated with protostellar cores. Based on the spatial extent of the groups of masers, we classify them as either outflow-associated or young stellar object (YSO)–associated. We identify 144 unique sites of maser emission: 23 are associated with H II regions and 94 with protostellar cores, of which 33 are associated with protostellar outflows and 18 with YSOs. The outflow-associated H₂O maser emission is confined to within <2000 au of the central continuum source, despite shocked SiO emission extending over tens of thousands of astronomical units. The YSO-associated masers show a lack of detections at 5 < V_rel < 30 km s⁻¹, which we suggest may be due to maser self-absorption. We show how H₂O masers trace the large-scale material flow in Sgr B2 North, also seen in SiO and millimeter continuum emission. Finally, we find that protostellar cores with associated H₂O masers tend to have brighter 3 mm continuum emission on average, although there is no strong correlation between maser brightness and continuum flux.

We present BVi multiband high-cadence observations of a Type II supernova (SN) KSP-SN-2022c from a star-forming galaxy at z ≃ 0.041 from its infant to nebular phase. Early light-curve fitting with a single power law is consistent with the first detection roughly 15 minutes after shock breakout (SBO). The SN light curves feature a rapid rise and decline across its luminous (V ≃ –18.41 mag) peak together with a short plateau. The presence of the short plateau and rapid postpeak decline place the SN within a small group of transitional type between Type II-P and II-L subtypes. Its broad and asymmetric H profiles with large emission-to-absorption ratios and its near-peak luminosity in excess of predictions from models of SN shock cooling both point to circumstellar interactions in this SN. Early colour evolution exhibits a short-lived blueward motion in B − V within the first few days and continuous reddening in V − i, inconsistent with simple blackbody heating. Our simulations of SN light curves estimate 13 M_⊙ and 680 R_⊙ for the mass and radius of the progenitor, respectively, together with circumstellar material (CSM) of 0.73 M_⊙ to account for the excess luminosity and rapid postpeak declines. We discuss the origin of its short plateau and early colour evolution in the context of partial envelope stripping of the progenitor star and a delayed SN SBO near the edge of the CSM, respectively, as indicated by our simulations. We establish a correlation between postpeak decline rates and CSM mass in Type II SNe, highlighting that CSM interactions play a major role in shaping the postpeak evolution of transitional types.

We present the optical discovery and multiwavelength follow-up observations of AT 2024kmq, a likely tidal disruption event (TDE) associated with a supermassive (M_BH ∼ 10⁸M_⊙) black hole in a massive galaxy at z = 0.192. The optical light curve of AT 2024kmq exhibits two distinct peaks: an early fast (timescale 1 day) and luminous (M ≈ −20 mag) red peak, then a slower (timescale 1 month) blue peak with a higher optical luminosity (M ≈ −22 mag) and featureless optical spectra. The second component is similar to the spectroscopic class of “featureless TDEs” in the literature, and during this second component we detect highly variable, luminous (L_X ≈ 10⁴⁴ erg s⁻¹), and hard (f_ν ∝ ν^−1.5) X-ray emission. Luminous (10²⁹ erg s⁻¹ Hz⁻¹ at 10 GHz) but unchanging radio emission likely arises from an underlying active galactic nucleus. The luminosity, timescale, and color of the early red optical peak can be explained by synchrotron emission, or alternatively by thermal emission from material at a large radius (R ≈ a few × 10¹⁵ cm). Possible physical origins for this early red component include an off-axis relativistic jet, and shocks from self-intersecting debris leading to the formation of the accretion disk. Late-time radio observations will help distinguish between the two possibilities.

We investigate two barred galaxies with nuclear structures, NGC 6951 and NGC 7716, to examine whether they host slow bars. Using Gemini/GMOS long-slit spectroscopy, we calculate the bar pattern speed with the Tremaine–Weinberg method and detect kinematically decoupled nuclear disks in both galaxies. We also measure the bar length and strength using Pan-STARRs images and identify a nuclear ring in NGC 6951 and a nuclear bar in NGC 7716 from Hubble Space Telescope/Planetary Camera images. Our results indicate that NGC 6951 hosts a slow, long, and strong bar, which likely evolved through interactions with the dark matter halo and contributed to the formation of both the nuclear disk and ring. We also find hints of a rapidly rotating oval structure within the primary bar, although it is not clearly seen in the imaging data. In contrast, the primary bar in NGC 7716 is too weak to be classified as a barred galaxy, while its nuclear disk and nuclear bar are unusually large, possibly due to tidal interactions or the weakness of the primary bar. These findings suggest that slow bars may be more observed in galaxies with nuclear structures and highlight the often underappreciated role of galaxy interactions in bar evolution.

Interstellar complex organic molecules (COMs) in solar-like young stellar objects (YSOs), particularly within protostellar disks, are of significant interest owing to their potential connection to prebiotic chemistry in emerging planetary systems. We report the discovery of a rotating feature enriched in COMs, including CH₃OH, CH₃CHO, and NH₂CHO, in the protostellar core G192.12-11.10. By constructing a YSO model, we find that the COM-rich feature is likely located within or near the boundary of the Keplerian disk. The image synthesis results suggest that additional heating mechanisms leading to a warm ring or a warm inner disk are required to reproduce the observed emission. We discuss possible origins of the COM-rich feature, particularly accretion shocks as a plausible cause for a warm ring. Additionally, molecules such as C¹⁸O, H₂CO, DCS, H₂S, and OCS exhibit distinct behavior compared to CH₃OH, indicating a range of physical and chemical conditions within the region. The observed kinematics of H₂S and OCS suggest that OCS resides in regions closer to the central protostar than H₂S, consistent with previous experimental studies.

This paper presents the spherically averaged 21 cm power spectrum derived from Epoch of Reionization (EoR) observations conducted with the Murchison Widefield Array (MWA). The analysis uses EoR0-field data, centered at (R.A. = 0h, decl. = −27^∘), collected between 2013 and 2023. Building on the improved methodology described in C. M. Trott et al. (2024), we incorporate additional data quality control techniques introduced in C. D. Nunhokee (2020). We report the lowest-power-level limits on the EoR power spectrum at redshifts z = 6.5, z = 6.8, and z = 7.0. These power levels, measured in the east–west polarization, are (30.2)² mK² at k = 0.18 h Mpc⁻¹, (31.2)² mK² at k = 0.18 h Mpc⁻¹, and (39.1)² mK² at k = 0.21 h Mpc⁻¹, respectively. The total integration time amounts to 268 hr. These results represent the deepest upper limits achieved by the MWA to date and provide the first evidence of the heated intergalactic medium at redshifts z = 6.5 to 7.0.

We present results from Identifying Dwarfs of MC Analog GalaxiEs (ID-MAGE), a survey aimed at identifying and characterizing unresolved satellite galaxies around 35 nearby LMC- and SMC-mass hosts (D = 4−10 Mpc). We use archival DESI Legacy Survey imaging data and perform an extensive search for dwarf satellites, extending out to a radius of 150 kpc (∼R_vir). We identify 355 candidate satellite galaxies, including 264 new discoveries. Extensive tests with injected galaxies demonstrate that the survey is complete down to M_V ∼ −9.0 (assuming the distance of the host) and μ_0,V ∼ 26 mag arcsec⁻² (assuming an n = 1 Sérsic profile). We perform consistent photometry, via Sérsic profile fitting, on all candidates and have initiated a comprehensive follow-up campaign to confirm and characterize candidates. Through a systematic visual inspection campaign, we classify the top candidates as high-likelihood satellites. On average, we find 4.0 ± 1.4 high-likelihood candidate satellites per LMC-mass host and 2.1 ± 0.6 per SMC-mass host, which is within the range predicted by cosmological models. We use this sample to establish upper and lower estimates on the satellite luminosity function of LMC-/SMC-mass galaxies. ID-MAGE nearly triples the number of low-mass galaxies surveyed for satellites with well-characterized completeness limits, providing a unique data set to explore small-scale structure and dwarf galaxy evolution around low-mass hosts in diverse environments.

Quasiperiodic oscillations (QPOs) in active galactic nuclei (AGNs) provide a powerful tool for probing the structure of the innermost accretion flow and corona around supermassive black holes. RE J1034+396, the most prominent AGN known to host an X-ray QPO, exhibits both short-term and long-term QPO evolution, offering a unique opportunity to investigate accretion disk and corona physics through its temporal behavior. We report a possible long-term (∼92.2 days) cyclic evolution of the QPO in RE J1034+396, joining the detected QPO (∼3730 s) and its short-term (∼17 ks) modulation to form a possible QPO triplet, which is potentially the first such structure identified in an AGN. By applying the relativistic precession model to the QPO triplet, we constrain the black hole mass to , consistent with independent estimates, and find a low dimensionless black hole spin of . We propose an exploratory model that involves a quasiperiodic ultrafast outflow (UFO) within the framework of the relativistic precession model, explaining the QPO lag reversal, the modulation of hard-band QPO amplitude by soft-band flux, and the long-term evolution of timing properties. Supporting evidence includes blueshifted emission and absorption lines indicating a strong UFO at ∼0.3c. This work provides new insights into the inner regions of AGN accretion disks and motivates further efforts in both numerical modeling and high-cadence timing observations.

The Dainotti relation empirically connects the isotropic plateau luminosity (L_X) in gamma-ray bursts (GRBs) and X-ray afterglows to the rest-frame time at which the plateau ends (), enabling both the standardization of GRBs and their use as cosmological probes. However, the precise physical mechanisms underlying this correlation remain an active area of research. Although magnetars, highly magnetized neutron stars, have been proposed as central engines powering GRB afterglows, traditional dipole spin-down radiation models fail to account for the full diversity of observed behaviors. This limitation necessitates a more comprehensive framework. We propose that multipolar magnetic field emissions from magnetars offer a plausible explanation for the Dainotti relation. Unlike simple dipole fields, higher-order multipolar configurations enable more complex energy dissipation processes. The coexistence of multiple components can plausibly explain the range of afterglow decay indices found from a sample of 238 GRBs with plateau features from the Swift-X-Ray Telescope database up to the end of 2024 December, the majority of which deviate from the dipolar prediction of α = −2, and more crucially, the spin-down physics yields a link between L_X and in a way that preserves the Dainotti correlation with a slope of b = −1, independent of the specific multipole order. Moreover, we find that the inclusion of higher-order multipoles can explain the range of plateau energies found in the Dainotti relations. Thus, a unified picture emerges in which multipolar fields are able to reproduce both the slope and the normalization of the correlation.

Using the Hubble Space Telescope/Space Telescope Imaging Spectrograph, ultraviolet (UV) extinction curves have been measured in M31 along 13 new sight lines, increasing the M31 sample to 17. This sample covers a wide area of M31, having galactocentric distances of 5–16 kpc, enabling the analysis of UV extinction curve variations over a large region of an external galaxy similar to the Milky Way with global galactic characteristics such as metallicity for the first time. No correlation is found between the extinction parameters and galactocentric distance, which might be expected if there is a radial metallicity gradient in M31. Most of the new UV extinction curves presented here are significantly different from the average extinction curves of the Milky Way, Large Magellanic Cloud (LMC), and Small Magellanic Cloud (SMC), but the average M31 extinction curve is similar to the average extinction curve in the 30 Dor region of the LMC. The wide range of extinction curves seen in each individual Local Group galaxy suggests that global galactic properties such as metallicity may be less important than the local environmental conditions, such as density, UV radiation field, and shocks along each sight line. The combined behavior of the Milky Way, LMC, SMC, and now M31 UV extinction curves supports the idea that there is a family of curves in the Local Group with overlapping dust grain properties between different galaxies.

We study the effect of the solar cycle on various magnetohydrodynamic (MHD) fluctuation modes using the linear mode decomposition technique developed by G. P. Zank et al. We decompose various MHD modes, including propagating modes: Alfvén (forward and backward), fast (forward and backward), and slow (forward and backward) modes, as well as nonpropagating structures: entropy and magnetic island modes, from solar wind intervals during both the minimum and maximum phases of solar cycle 23. We find that the amplitudes of different modes corresponding to fluctuations in density, magnetic field, and velocity vary over the solar cycle, with larger amplitudes observed during the solar maximum compared to the solar minimum. The fluctuating energy of these modes is ∼1.5–4.5 times larger during the solar maximum. The frequency spectrum shows that the entropy mode exhibits the largest fluctuating power among density fluctuations, surpassing the contributions of fast and slow magnetosonic modes during both solar maximum and minimum intervals. For magnetic field fluctuations, the dominant contributors are the magnetic island mode, followed by the Alfvén modes. The Alfvén modes dominate the overall velocity fluctuations. This study provides observational evidence for the influence of the solar cycle on linear MHD modes.

During the 2022 outburst of SGR 1935+2154, a fast radio burst (FRB)-like event (FRB 20221014A) and X-ray activities occurred between two spin-up glitches, suggesting these glitches may connect to multiwavelength phenomenology. However, the mechanisms altering the magnetar’s magnetosphere to enable radio emission remain unclear. This study presents high-cadence Neutron Star Interior Composition Explorer and Nuclear Spectroscopic Telescope Array observations revealing spectral changes in burst and persistent emission. Hardness ratio and spectral analysis reveal significant changes during an “intermediate flare” 2.5 hr before FRB 20221014A. This 40 s flare, releasing >(6.3 ± 0.2) × 10⁴⁰ erg, coincides with a rapid spectral softening in both burst and persistent emission, and a notable decrease in the burst occurrence rate. The intermediate flare is bright enough to be detected if placed at a few megaparsecs, and would appear as a fast X-ray transient. This implies that the connection between magnetar X-ray activity and FRBs can be observed in the local Universe. Postflare burst spectra peak near 5 keV, resembling the characteristics of the FRB-associated X-ray burst of 2020. Such change persisted for a few hours, implying magnetospheric evolution on similar timescales. However, no radio emission was detected from postflare bursts, suggesting that FRB emission requires conditions beyond peculiar short bursts. The burst waiting times exhibit a broken power-law distribution, likely resulting from contamination by enhanced persistent emission. Although the bursts appear randomly distributed in the spin phase, the hardness ratio profile as a function of spin phase follows that of the persistent emission, indicating that X-ray bursts originate at low altitudes.

In kinetic theory, the classic nΣv approach calculates the rate of particle interactions from local quantities: the number density of particles n, the cross section Σ, and the average relative speed v. In stellar dynamics, this formula is often applied to problems in collisional (i.e., dense) environments such as globular and nuclear star clusters, where blue stragglers, tidal capture binaries, binary ionizations, and microtidal disruptions arise from rare close encounters. The local nΣv approach implicitly assumes the ergodic hypothesis, which is not well motivated for the densest star systems in the Universe. In the centers of globular and nuclear star clusters, orbits close into 1D ellipses because of the degeneracy of the potential (either Keplerian or harmonic). We find that the interaction rate in perfectly Keplerian or harmonic potentials is determined by a global quantity—the number of orbital intersections—and that this rate can be far lower or higher than the ergodic nΣv estimate. However, we find that, in most astrophysical systems, deviations from a perfectly Keplerian or harmonic potential (due to, e.g., granularity or extended mass) trigger sufficient orbital precession to recover the nΣv interaction rate. Astrophysically relevant failures of the nΣv approach only seem to occur for tightly bound stars orbiting intermediate-mass black holes, or for the high-mass end of collisional cascades in certain debris disks.

Unveiling the evolutionary history of galaxies necessitates a precise understanding of their physical properties. Traditionally, astronomers achieve this through spectral energy distribution (SED) fitting. However, this approach can be computationally intensive and time-consuming, particularly for large data sets. This study investigates the viability of machine learning (ML) algorithms as an alternative to traditional SED fitting for estimating stellar masses in galaxies. We compare a diverse range of unsupervised and supervised learning approaches, including prominent algorithms such as K-means, HDBSCAN, Parametric t-Distributed Stochastic Neighbor Embedding (Pt-SNE), principal component analysis, Random Forest, and self-organizing maps (SOM) against the well-established LePhare code, which performs SED fitting as a benchmark. We train various ML algorithms using simple model SEDs in photometric space, generated with the BC03 code. These trained algorithms are then employed to estimate the stellar masses of galaxies within a subset of the COSMOS survey data set. The performance of these ML methods is subsequently evaluated and compared with the results obtained from LePhare, focusing on both accuracy and execution time. Our evaluation reveals that ML algorithms can achieve comparable accuracy to LePhare while offering significant speed advantages (1000–100,000 times faster). K-means and HDBSCAN emerge as top performers among our selected ML algorithms. Supervised learning algorithms like Random Forest and manifold learning techniques such as Pt-SNE and SOM also show promising results. These findings suggest that ML algorithms hold significant promise as a viable alternative to traditional SED-fitting methods for estimating the stellar masses of galaxies.

We characterize stellar, gas, and dark matter mass distributions for 17 nearby massive disk galaxies from the PHANGS sample. This allows us to compute the gravitational potential that vertically confines the interstellar gas and determines its equilibrium scale height and weight. We first combine dynamical mass constraints from existing CO and H i rotation curves, together with stellar and gas mass estimates from near-infrared, CO, and H i data. These estimates incorporate current best practices in modeling stellar mass-to-light ratios and CO-to-H₂ conversion factor variations. Then, we fit joint stellar–gas–dark matter mass models to the rotation curves, adopting the classic maximal disk assumption to account for remaining zero-point uncertainties on the stellar mass-to-light ratio. After obtaining three-component radial mass profiles, we calculate the vertical equilibrium gas scale height and interstellar medium (ISM) weight in the combined gravitational potential. We find the gas scale height H_gas increases from ≲100 pc in the inner disks to >500 pc at large radii, consistent with observations of our Galaxy and other edge-on galaxies. The gas weight is dominated by stellar gravity at small radii, but the gas and dark matter gravity often become important beyond 3–6 times the stellar disk radial scale length. Both our gas scale height and weight estimates are dependent on the treatment of stellar disk scale height H_⋆, with H_gas varying by 30%–40% when H_⋆ varies by a factor of 3. The relationship between our refined ISM weight estimates and local star formation surface density generally agrees with previous observations and predictions from theory and simulations.

The active galactic nucleus (AGN) channel for the formation of binary black hole (BBH) mergers has been previously studied as a potential formation channel for the merging compact binaries observed by the LIGO–Virgo–KAGRA (LVK) scientific collaboration. The first two papers in this series explored the McFACTS code for the evolution of black hole orbits in AGN accretion disks for individual galaxy models and described the characteristics of predicted BBH populations in realizations of those models (such as the correlation between mass ratio and aligned spin). In this work, we explore the impact of the properties of AGN host galaxies and assume an AGN lifetime and cosmological model for the density of AGN in a universe like our own. By sampling from an inferred population of AGN, we marginalize over galaxy mass to predict a population of BBH mergers observable by modern ground-based gravitational-wave observatories. We find that for reasonable assumptions, AGN disk environments may account for massive BBH mergers such as GW190521 and GW190929_012149. We find that the majority of observable BBH mergers from our simulation are expected to originate in galaxies with a supermassive black hole between 10⁷M_⊙ and 10^9.4M_⊙. We also find that if hierarchical mergers from AGN disks account for a substantial part of the LVK population, our current models require an AGN lifetime of 0.5–2.5 Myr.

Atmospheric escape shapes exoplanet evolution and star–planet interactions, with He I 10830 Å absorption serving as a key tracer of mass loss in hot gas giants. However, transit depths vary significantly across observed systems for reasons that remain poorly understood. HD209458b, the archetypal hot-Jupiter, exhibits relatively weak He I 10830 Å and Hα absorption, which has been interpreted as evidence for a high H/He ratio (98/2), possibly due to diffusive separation. To investigate this possibility and other processes that control these transit depths, we reassess excitation and de-excitation rates for metastable helium and explore the impact of diffusion processes, stellar activity, and tidal forces on the upper atmosphere and transit depths using a model framework spanning the whole atmosphere. Our model reproduces the observed He I transit depth and Hα upper limit, showing strong diffusive separation. We match the observations assuming a photoelectron efficiency of 20%–40%, depending on the composition of the atmosphere, corresponding to mass-loss rates of 1.9–3 × 10¹⁰ g s⁻¹. We find that the He I 10830 Å transit depth is sensitive to both stellar activity and diffusion processes, while Hα is largely unaffected due to its strong dependence on Lyα excitation. These differences may help explain the system-to-system scatter seen in population-level studies of the He I line. While He I data alone may not tightly constrain mass-loss rates or temperatures, they do confirm atmospheric escape and help narrow the viable parameter space when interpreted with physically motivated models. Simultaneous observations of He I, Hα, and stellar activity indicators provide powerful constraints on upper atmosphere dynamics and composition, even in the absence of full transmission spectra.

We present high-resolution data of IRAS 23077+6707 (“Dracula’s Chivito”) with the Submillimeter Array (SMA at 1.33 mm/225.5 GHz) and the Northern Extended Millimeter Array (NOEMA at 2.7 mm/111.7 GHz and 3.1 mm/96.2 GHz). IRAS 23077+6707 is a highly inclined and newly discovered protoplanetary disk, first reported in 2024. We combine SMA baselines from the compact, extended, and very extended arrays, and NOEMA baselines from its A and C configurations, and present continuum images with resolution ≲08, which constitute the first subarcsecond resolution maps of IRAS 23077+6707. The images show extended linear emission that spans 56–61 as expected for a radially extended, highly inclined protoplanetary disk. Accompanied with lower-resolution data, we show that the disk has a steep spectral index, ranging from α = 3.2–3.9. We present evidence of multiple radial emission peaks and troughs in emission, which may originate in disk rings and a central cavity. We further present evidence that these radial structures are asymmetric; hosting a significant brightness asymmetry, with emission enhanced by up to 50% in the north versus the south. We discuss hypotheses about the potential origins of these features, including the possibility that IRAS 23077+6707 hosts a rare example of an eccentric protoplanetary disk, which can induce these radially asymmetric structures. We present a simple eccentric continuum model of IRAS 23077+6707, and show, for an eccentricity of e ≈ 0.26, that this can reproduce the bulk morphology of the emission.

The Milky Way is home to a thin disk that can be defined via kinematics and/or elemental abundances. The elemental abundance-defined thin disk, also called the low-alpha disk, is generally thought to comprise stars on planar, circular orbits that approximate the circular velocity curve. While this is an apt description for the majority of stars with thin-disk-like abundances, there are a number of interesting exceptions. In this analysis, we identify and investigate ∼70 stars with thin-disk-like abundances and very slow or retrograde Galactocentric azimuthal velocities. These stars could be kinematical outliers of the thin disk or elemental abundance outliers of the halo. Focusing first on the former, we introduce a number of mechanisms that could alter a thin disk orbit and cause the azimuthal velocity to become slow or retrograde. We then determine signatures for each mechanism and assess whether that mechanism is unlikely, plausible, or consistent given each star’s reported properties. We find that at least one mechanism is plausible for each star, and the mechanism with the highest number of consistent candidate stars is dynamical ejection from stellar clusters. We next discuss scenarios that could produce halo stars with thin-disk abundances, and again identify stars that could be connected to these mechanisms. With this sample, we investigate rare processes, such as binary disruption by the central supermassive black hole, while also providing a unique perspective into the chemo-dynamics and structural components of the Milky Way.

Extreme emission line galaxies (EELGs) at high redshifts are considered key contributors to cosmic reionization at z > 6 due to their higher ionization efficiencies. We have identified 119 Hβ + [O iii] emitters at z ∼ 7 selected by a flux excess in the medium-band filter F410M in the public James Webb Space Telescope Cycle-1 fields. Our emitters exhibit a wide range in rest-frame Hβ + [O iii] equivalent width (EWs), 420 < EW₀ / Å < 6850 (with the median value of ∼1700 Å). Among them, 19 are EW₀ > 3000 / Å, which represent extreme populations even in the context of recent findings with JWST. They are characterized by (i) low stellar mass (∼3 × 10⁷M_⊙), (ii) blue colors (β_UV ∼ −2.2), and (iii) low dust attenuation (A_V ∼ 0.1 mag). We discuss the physical mechanisms responsible for the observed high rest-frame Hβ + [O iii] EWs, including (1) photoionization by active galactic nucleus (AGN), (2) stellar photoionization in the vicinity of H ii regions, and (3) radiative shocks powered by outflows either from AGN or massive stars. Notably, we find 13 emitters with spatially offset Hβ + [O iii] emission compared to the UV and stellar components. Given the absence of obvious signatures of actively accreting black holes, these emitters are likely under strong feedback-driven winds from massive stars. Lastly, we report a unique overdensity of EELGs in one of the observed fields. The discovery of such a “star-bursting” overdensity supports the idea that large ionizing bubbles formed around some EEGLs in the early Universe.

The symbiotic channel of Type Ia supernovae progenitors is crucial for explaining the observed circumstellar material in some Type Ia supernovae. While extensive numerical and observational efforts have been dedicated to exploring their progenitor systems, limited emphasis has been placed on studying the surviving companions arising from the symbiotic channel. In this paper, we present a numerical study of symbiotic systems using MESA simulated stars as potential Type Ia supernova progenitors. We conduct 1260 binary stellar evolution simulations, over a wide range of parameters, incorporating the optically thick wind model developed by I. Hachisu et al., and predict the postimpact evolution of these surviving companions. We classify four types of progenitor systems based on the evolutionary stage of the companion at the onset of the explosion: red giant companions, with or without a prior helium flash event, and asymptotic giant branch companions, with or without the thermal pulsing phase. After the supernova impact, a blue dwarf star with either a helium or carbon–oxygen core is left behind. However, if a small portion of the envelope (≳0.3%) remains on the core of the surviving companion, the overall postsupernova evolution may remain similar to its preexplosion state, albeit slightly fainter, making observation a challenging endeavor.

Internal gas inflows driven by galaxy mergers are considered to enhance star formation rates (SFRs), fuel supermassive black hole growth, and stimulate active galactic nuclei (AGNs). However, quantifying these phenomena remains a challenge, due to difficulties both in classifying mergers and in quantifying galaxy and AGN properties. We quantitatively examine the merger–SFR–AGN connection using Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) galaxies using novel methods for both galaxy classification and property measurements. Mergers in HSC-SSP observational images are identified through fine-tuning Zoobot, a pretrained deep representation learning model, using images and labels based on the Galaxy Cruise project. We use galaxy and AGN properties that were produced by fitting Galaxy and Mass Assembly spectra using the spectral energy distribution fitting code ProSpect, which fits panchromatically across the far-ultraviolet through far-infrared wavelengths and obtains galaxy and AGN properties simultaneously. Small differences are seen in SFR and AGN activity between mergers and controls, with ΔSFR = −0.009 ± 0.003 dex, Δf_AGN = −0.010 ± 0.033 dex, and ΔL_AGN = 0.002 ± 0.025 dex. After further visual purification of the merger sample, we find ΔSFR = −0.033 ± 0.014 dex, Δf_AGN = −0.024 ± 0.170 dex, and ΔL_AGN = 0.019 ± 0.129 dex for pairs, and ΔSFR = −0.057 ± 0.024 dex, Δf_AGN = 0.286 ± 0.270 dex, and ΔL_AGN = 0.329 ± 0.195 dex for postmergers. These numbers suggest secular processes being an important driver for star formation and AGN activity, and present a cautionary tale when using longer-timescale tracers.

The existence of nearby discrete cosmic-ray (CR) sources can lead to many interesting effects on the observed properties of CRs. Recent measurements of CRs with the CALET and the DAMPE experiments have revealed a bump-like new feature in the proton and helium spectra in the energy range ∼(1–100) TeV n⁻¹. The origin of the feature is not clearly understood. In this paper, considering an improved and more detailed analysis than previous works, and using updated age and distance estimates of nearby supernova remnants (SNRs) along with an energy-dependent escape process for CRs from the remnants, we show that the spectral bump can be explained by the contribution of CRs from the nearby SNRs, in particular the Vela remnant. We also show that the contribution from the nearby remnants agrees well with the observed spectra of the heavier CR elements from carbon to iron, as well as with the measured all-particle CR spectrum beyond the knee region when combined with a background flux of CRs originating from distant SNRs.

We present James Webb Space Telescope (JWST)/NIRSpec PRISM spectroscopic characterization of GHZ9 at z = 10.145 ± 0.010, currently the most distant source detected by the Chandra X-ray Observatory. The spectrum reveals several UV high-ionization lines, including C II, Si IV, N IV], C IV, He II, O III], N III], and C III]. The prominent rest-frame equivalent widths (EW(C IV) ≃ 65 Å, EW(O III]) ≃ 28 Å, and EW(C III]) ≃ 48 Å) show the presence of a hard active galactic nucleus (AGN) radiation field, while line ratio diagnostics are consistent with either AGN or star formation as the dominant ionizing source. GHZ9 is nitrogen-enriched (6–9.5 (N/O)_⊙), carbon-poor (0.2–0.65 (C/O)_⊙), metal-poor (Z = 0.01–0.1 Z_⊙), and compact (<106 pc), similarly to GN-z11, GHZ2, and recently discovered N-enhanced high redshift objects. We exploited the newly available JWST/NIRSpec and NIRCam data set to perform an independent analysis of the Chandra data confirming that GHZ9 is the most likely JWST source associated with X-ray emission at 0.5–7 keV. Assuming a spectral index Γ = 2.3 (1.8), we estimate a black hole (BH) mass of 1.60 ± 0.31 (0.48 ± 0.09) × 10⁸M_⊙, which is consistent either with Eddington-accretion onto heavy (≥10⁶M_⊙) BH seeds formed at z = 18 or super-Eddington accretion onto a light seed of ∼10²–10⁴M_⊙at z = 25. The corresponding BH-to-stellar mass ratio M_BH/M_star = 0.33 ± 0.22 (0.10 ± 0.07), with a stringent limit >0.02, implies an accelerated growth of the BH mass with respect to the stellar mass. GHZ9 is the ideal target to constrain the early phases of AGN–galaxy coevolution with future multifrequency observations.

The typical amount of molecular hydrogen (H₂) in interstellar ices is not known, but significant freeze-out of H₂ on dust grains is not expected. However, chemical models ubiquitously predict large amounts of H₂ freeze-out in dense cloud conditions, and specialized treatments are needed to control the H₂ population on grains. Here we present a numerical desorption model where the effect of weak heating events induced by cosmic rays (CRs) that heat grains to temperatures of a few tens of kelvin at high frequencies is included, improving upon earlier desorption models that only consider strong heating events (maximum grain temperature close to 100 K) that occur at a low frequency. A temperature of a few tens of kelvin is high enough to induce efficient desorption of H₂, but we find that even the weak heating events do not occur often enough to lead to significant H₂ desorption. Taking the weak heating events into account does affect the predicted abundances of other lightly bound species, but the effect is restricted to low column densities. We make here the canonical assumption that the grains are spherical with a radius of 0.1 μm. It is conceivable that in the case of a grain size distribution, weak heating events could provide a boost to H₂ desorption coming off small grains, which are the most numerous. Further studies are still required to better quantify the role of CRs in the desorption of H₂ and other weakly bound species.

Fast radio bursts (FRBs) are extragalactic radio transients that offer valuable insight into the intergalactic medium (IGM). However, the dispersion measure (DM) contributed by the IGM (DM_IGM) is degenerate with that from the host galaxy (DM_host), necessitating calibration of the DM_IGM−z relation for cosmological applications. As DM_host is expected to correlate with host galaxy properties, it is feasible to estimate DM_host from observable host characteristics. In this study, we conduct spectral energy distribution and Sérsic model fittings to derive the parameters of FRB host galaxies. Then, we examine the correlations between the excess dispersion measure (DM_exc) and host galaxy parameters, including star formation rate, stellar mass, specific star formation rate (sSFR), inclination angle, and projected area. A tight correlation between DM_exc and sSFR is found. This correlation is utilized to estimate DM_host of FRBs, providing a method to calibrate the DM_IGM–z relation. This approach leads to a notable improvement in calibration performance.

T Coronae Borealis is the nearest symbiotic recurrent nova. Twice in the last two centuries, in 1866 and 1946, the accreted material ignited on the surface of the white dwarf via runaway thermonuclear fusion reactions and produced a nova eruption. Both eruptions occurred approximately midway through a transient state of high luminosity. A possible explanation of such a state is a dwarf-nova-like outburst, which may arise from a transient increase in the mass-transfer rate of the donor star. We simulate the response of an accretion disk to an event of enhanced mass-transfer that is “interrupted” by a pre-eruption dip associated with the convective phase leading to the thermonuclear runaway. We model the resulting optical light curve using the parameters of the T CrB binary. Our model represents the first attempt to reproduce the transient high-accretion state. The observed brightening can be satisfactorily reproduced by models of an accretion disk with a viscosity parameter α = 3, an event of enhanced mass-transfer with a duration of Δt = 15 yr, and quiescent and high-state mass-transfer rates of 2.0 × 10⁻⁹M_⊙ yr⁻¹ and 1.9 × 10⁻⁷M_⊙ yr⁻¹, respectively, while the pre-eruption dip can be reproduced by the small, accelerated expansion of the inner disk's radius, at an average velocity of 0.02 km s⁻¹. Our model is also capable of reproducing the observed changes in color of T CrB throughout the transient event.

We present the first high-precision proper-motion catalog, tied to the International Celestial Reference System (ICRS), of infrared astrometric reference stars within R ≤ 25″ (1 pc) of the central supermassive black hole at the Galactic center (GC). This catalog contains ∼2900 sources in a highly extinguished region that is inaccessible via Gaia. New astrometric measurements are extracted from Hubble Space Telescope (HST) observations (14 epochs, 2010–2023) and transformed into the ICRS using 40 stars in common with Gaia-DR3. We implement a new method for modeling proper motions via Gaussian processes that accounts for systematic errors, greatly improving measurement accuracy. Proper-motion and position measurements reach precisions of ∼0.03 mas yr⁻¹ and ∼0.11 mas, respectively, representing a factor of ∼20 improvement over previous ICRS proper-motion catalogs in the region. These measurements define a novel HST–Gaia reference frame that is consistent with Gaia-CRF3 to within 0.025 mas yr⁻¹ in proper motion and 0.044 mas in position, making it the first ICRS-based reference frame precise enough to probe the distribution of extended mass within the orbits of stars near SgrA*. In addition, HST-Gaia provides an independent test of the radio measurements of stellar masers that form the basis of current GC reference frames. We find that the HST–Gaia and radio measurements are consistent to within 0.041 mas yr⁻¹ in proper motion and 0.54 mas in position at 99.7% confidence. Gaia-DR4 is expected to reduce the HST–Gaia reference-frame uncertainties by another factor of ∼2, further improving the reference frame for dynamical studies.

We present a near-complete spectral energy distribution (SED) for an extrasolar world: the T8 brown dwarf 2MASS J04151954−0935066. Spanning from optical to mid-infrared (0.7–20.4 μm) wavelengths, the SED for this substellar atmosphere is constructed from new James Webb Space Telescope (JWST) NIRSpec G395H (R ∼ 2700) and Magellan Folded-port InfraRed Echellete (FIRE) echelle (R ∼ 8000) near-infrared spectra, along with MIRI mid-infrared photometry complemented by spectra from Keck I, Infrared Telescope Facility, Magellan, AKARI, Spitzer, and photometry from various surveys and missions. The NIRSpec G395H spectrum reveals strong molecular absorptions from NH₃, CH₄, H₂S, CO₂, and H₂O at approximately 3.00, 3.35, 3.95, 4.25, and 5.00 μm, respectively, along with the presence of a CO absorption feature detected mainly at ∼4.6 μm. We detect no absorption of near-infrared K i doublets in the R ∼ 8000 FIRE spectra. In the mid-infrared Infrared Spectrograph spectrum, we tentatively identify a new CO₂ feature at 14–16 μm. The comprehensive SED allows us to empirically constrain bolometric luminosity, effective temperature, mass, and radius. Additionally, we demonstrate that the NIRSpec G395H resolution, the highest allowable by JWST, enables a precise radial velocity measurement of 47.1 ± 1.8 km s⁻¹ for the object, in agreement with previous measurements.

Understanding the impact of baryonic feedback on the small-scale (k ≳ 1 h Mpc⁻¹) matter power spectrum is a key astrophysical challenge, and essential for interpreting data from upcoming weak-lensing surveys, which require percent-level accuracy to fully harness their potential. Astrophysical probes, such as the kinematic and thermal Sunyaev–Zel’dovich effects, have been used to constrain feedback at large scales (k ≲ 5 h Mpc⁻¹). The sightline-to-sightline variance in the fast radio bursts (FRBs) dispersion measure (DM) correlates with the strength of baryonic feedback and offers unique sensitivity at scales up to k ∼ 10 h Mpc⁻¹. We develop a new simulation-based formalism in which we parameterize the distribution of DM at a given redshift, p(DM∣z), as a log-normal with its first two moments computed analytically in terms of cosmological parameters and the feedback-dependent electron power spectrum P_ee(k, z). We find that the log-normal parameterization provides an improved description of the p(DM∣z) distribution observed in hydrodynamical simulations as compared to the standard F-parameterization. Our model robustly captures the baryonic feedback effects across a wide range of baryonic feedback prescriptions in hydrodynamical simulations, including IllustrisTNG, SIMBA, and Astrid. Leveraging simulations incorporates the redshift evolution of the DM variance by construction and facilitates the translation of constrained feedback parameters to the suppression of matter power spectrum relative to gravity-only simulations. We show that with 10⁴ FRBs, the suppression can be constrained to percent-level precision at large scales and ∼10% precision at scales k ≳ 10 h Mpc⁻¹ with prior-to-posterior 1σ constraint width ratio ≳20.

We study the transmission and characteristics of turbulent magnetohydrodynamic (MHD) fluctuations from upstream to downstream regions of interplanetary (IP) shocks using the linear mode decomposition (LMD) technique of G. P. Zank et al. We perform a superposed epoch analysis (SEA) of 84 fast-forward quasi-perpendicular shock events observed by the Wind spacecraft at 1 au. We find that the intensities of various MHD modes associated with density, velocity, and magnetic field fluctuations are enhanced by ∼4–14 times across the shock. On average, the amplitude enhancement of velocity fluctuations across the shock is smaller than that of density and magnetic fluctuations. The frequency spectra reveal that the entropy, magnetic island, and Alfvén modes are the dominant contributors to the overall density, magnetic field, and velocity fluctuations, respectively, both upstream and downstream. The SEA reveals that the downstream spectral slope of various modes closely follows a f^−5/3 (or k^−5/3) power law, but the upstream spectra are slightly flatter than the downstream curves. A steeper spectral slope downstream suggests an increased energy dissipation or a stronger turbulent cascade. These findings show the usefulness of the LMD technique to decompose turbulent fluctuations into fundamental linear MHD modes, providing a deeper understanding of turbulence upstream and downstream of IP shocks.

We present an M87 molecular line search from archival Atacama Large Millimeter/submillimeter Array imaging, covering the circumnuclear disk (CND) as well as ionized gas filaments and dusty cloud regions. We find no evidence for CO emission in the central ∼kiloparsec and place an upper limit of M_⊙ in the atomic gas CND region, a factor of 20× lower than previous surveys. During this search, we discovered extragalactic CO absorption lines in the J = 1−0, 2−1, and 3−2 transitions against the bright (jansky-scale) active nucleus. These CO lines are narrow (∼5 km s⁻¹) and blueshifted with respect to the galaxy’s systemic velocity by −75 to −84 km s⁻¹. This CO absorber appears to be kinematically distinct from outflowing atomic gas seen in absorption. Low integrated opacities ranging from τ_CO ∼ 0.02−0.06 km s⁻¹ and a column density N_CO ≈ (1.2 ± 0.2) × 10¹⁵ cm⁻² translate to cm⁻². CO excitation temperatures spanning T_ex ∼ 8–30 K do not follow local thermodynamic equilibrium (LTE) expectations, and non-LTE radex radiative transfer modeling of the CO absorber is consistent with a number density cm⁻³ embedded in a ∼60 K environment. Taken together, the observed CO absorption lines are most consistent with a thin, pressure-confined filament seen slightly off-center from the M87 nucleus. We also explore the impact of residual telluric lines and atmospheric variability on narrow extragalactic line identification and demonstrate how bandpass calibration limitations may introduce broad but very low signal-to-noise ratio and spurious absorption and emission signatures.

We report the serendipitous discovery of an absorption feature at 4.8 keV in the NuSTAR spectra of ESP 39607, a Seyfert 2 galaxy at z = 0.201, observed in 2023 May and 2024 August. The feature is detected in both observations with individual significance levels between 2σ and 3σ, computed with multiple statistical methods. The combined probability of detecting it in both observations is ≳4σ. The absorption feature is consistent with an ultrafast inflow (UFI) potentially associated with Fe xxv or Fe xxvi Kα transitions. The inferred inflow velocity is ∼0.15–0.20c, with an estimated launching radius of 22–89R_g, depending on the assumed iron transition and whether radiation pressure is accounted for. Photoionization modeling associates the UFI primarily with Fe xxv Kα absorption, blended with a minor contribution from Fe xxvi Kα. Alternative explanations, including associations with the warm-hot intergalactic medium or outflows of lighter elements, are investigated but found unlikely. If confirmed, this detection represents a rare example of a UFI, providing valuable evidence into extreme and/or nonstandard accretion processes near supermassive black holes. Follow-up observations with higher-resolution X-ray spectroscopy, such as with XMM-Newton or XRISM, will be essential to confirm the nature of this feature and better constrain the physical mechanisms driving it.

We report multifrequency Very Long Baseline Array (VLBA) observations at 2.3 and 8.4 GHz of three nearby ultraluminous infrared galaxies, identified via mid-infrared spectroscopic analyses as hosting deeply embedded active galactic nuclei (AGNs). Milliarcsecond-scale observations at both frequencies reveal compact continuum emission in IRAS F00188−0856 and IRAS F01298−0744, accounting for ∼10% of the flux density measured on arcsecond scales. The nondetection in IRAS F00091−0738 and the lower limit on the intrinsic 8.4 GHz brightness temperature of 10^6.1 K in IRAS F01298−0744 yield no conclusive evidence of AGN-driven radio emission, whereas the measurement of 10^7.8 K in IRAS F00188−0856 confirms an AGN origin. Thus, the mid-infrared AGN classification remains robust, with at least one object exhibiting compact radio emission indicative of AGN activity. We further investigate the high-frequency spectral steepening observed in all three galaxies. In each case, this steepening arises from spectral aging in diffuse kiloparsec-scale emission, which is resolved out by the VLBA observations. One possible explanation for the steepening of the sample is merger-induced particle acceleration. IRAS F00188−0856 exhibits a peaked radio spectrum, characteristic of a young radio source, with the high-frequency steepening attributable to this AGN activity. Consequently, the spectral steepening at high frequencies arises from particles accelerated by merger dynamics or AGN activity.

We explore the differences in gas-rich field ultra-diffuse galaxies (UDGs) and diffuse classical dwarf galaxies using an extensive atomic gas (H I) follow-up survey of optically selected UDG candidates from the Systematically Measuring Ultra-diffuse Galaxies (SMUDGes) catalogue. We also compare the SMUDGes-H I observations with two state-of-the-art cosmological hydrodynamical simulations: Numerical Investigation of a Hundred Astrophysical Objects (NIHAO), where UDGs form through a series of bursty star formation episodes and Romulus25, where UDGs form as a result of major mergers that temporarily increase their spin. Although the suggested formation scenarios for UDGs within these simulations are different, the present-day H I masses M_{H I}, stellar masses M_*, and star formation rates of simulated galaxies are qualitatively and quantitatively consistent with each other and with the observed SMUDGes-H I sample. We find that when controlling for M_*, there is a positive correlation between the gas richness M_{H I}/M_* and the effective optical radius R_eff, and that this trend is not different between the UDG and dwarf populations, within the measured scatter. Taken together, our results suggest that gas-rich, star-forming UDGs and dwarfs are not distinct galaxy populations, either observationally or in simulations.

E+A galaxies represent a class of recently quenched objects, with spectra that show evidence of a previous substantial starburst and strong Balmer absorption lines indicative of A-type stellar populations. Using an SDSS-IV MaNGA–selected sample of E+A galaxies, we identify a matching sample in the TNG50 simulation to study their evolutionary histories. Additionally, we identify a sample of generic post-starburst (PSB) galaxies based on their star formation histories (SFHs) from the MaNGA Pipe3D value-added catalog. We find that PSB-like SFHs make up a similar fraction of galaxies in TNG50 (0.9% compared to MaNGA’s ∼1%). Matching galaxies based solely on their stellar masses and metallicities in TNG50 does not result in a sample with PSB-like histories. We analyzed the chemical enrichment histories of our selected simulated galaxy samples and found that both PSB and E+A galaxies exhibit a distinct episode of rapid enrichment when compared to galaxies in TNG50 with a similar stellar mass range. These galaxies are typically metal-poor before undergoing an extended ∼2 Gyr starburst, during which a phase of rapid chemical enrichment occurs over the first ∼300 Myr. The final systems are generally more metal-rich than the average galaxy in TNG50, while the MaNGA data do not show this trend. This suggests that PSB galaxies undergo unique evolutionary processes as they transition from starburst activity to quiescence. Further studies are needed to determine whether these galaxies originate from truly metal-poor progenitors and to better understand their subsequent evolution.

We investigate the high-ionization, narrow [Ne V] λ3427 line emission in a sample of over 340 ultrahard X-ray (14–195 keV) selected active galactic nuclei (AGN) drawn from the BAT AGN Spectroscopic Survey project. The analysis includes measurements in individual and stacked spectra and considers several key AGN properties such as X-ray luminosity, supermassive black hole (SMBH) mass, Eddington ratios, and line-of-sight column density. The [Ne V] λ3427 line is robustly detected in ≈43% (146/341) of the AGN in our sample, with no significant trends between the detection rate and key AGN/SMBH properties. In particular, the detection rate remains high even at the highest levels of obscuration (>70% for ). On the other hand, even some of our highest signal-to-noise spectra (S/N > 50) lack a robust [Ne v] detection. The typical (median) scaling ratios between [Ne v] line emission and (ultra)hard X-ray emission in our sample are and . The scatter on these scaling ratios, ≲0.5 dex, is comparable to, and indeed smaller than, what is found for other commonly used tracers of AGN radiative outputs (e.g., [O III] λ5007). Otherwise, we find no significant relations between the (relative) strength of [Ne v] and the basic AGN/SMBH properties under study, in contrast with simple expectations from models of SMBH accretion flows. Our results reaffirm the usability of [Ne v] as an AGN tracer even in highly obscured systems, including dual AGN and high-redshift sources.

We present timing and spectral analyses of Neutron star Interior Composition Explorer (NICER), Nuclear Spectroscopic Telescope Array (NuSTAR), and IXPE observations of the magnetar 1E 1841−045 covering 82 days following its 2024 August bursting activity as well as radio observations utilizing MeerKAT and Effelsberg. We supplement our study with a historical NuSTAR observation and all 2024 preoutburst NICER observations. The outburst is marked by an X-ray flux enhancement of a factor of 1.6 compared to the historical level, predominantly driven by a newly formed nonthermal emitting component with a photon index Γ = 1.5. This flux showed a 20% decay at the end of our monitoring campaign. The radio monitoring did not reveal any pulsed radio emission with an upper limit of 20 mJy and 50 mJy ms on the mean flux density and single pulse fluence, respectively. We detect a spin-up glitch at outburst onset with Δν = 6.1 × 10⁻⁸ Hz and Hz s⁻¹, consistent with the near universality of this behavior among the continuously monitored magnetars. Most intriguingly, the 1E 1841−045 2–10 keV pulse profile is markedly different compared to preoutburst: it shows a new, narrow (0.1 cycle) peak that appears to shift toward merging with the main, persistently present, pulse. This is the second case of pulse-peak migration observed in magnetars after SGR 1830−0645, and the two sources exhibit a similar rate of phase shift. This implies that this phenomenon is not unique and might present itself in the broader population. The newly formed peak for 1E 1841−045 is nonthermal, with emission extending to ≳20 keV, in contrast to the case of SGR 1830−0645. Our results are consistent with an untwisting magnetic field bundle with migration toward the magnetic pole, perhaps accompanied by plastic motion of the crust.

We study the stability of a hot saturated gas coexisting with condensed particles in an optically thin medium. Such a situation may be obtained downstream of a shock, at condensation fronts, or in vaporizing impacts. We show that the gas–particle mixture is subject to a thermal instability whereby a region of lower temperature and higher condensate density cools faster to condense faster. If the region of runaway condensation has a sound-crossing time shorter than its cooling time, then it accretes more mass, in gas and particles, from its higher-pressure surroundings. Numerical integration of the linearized perturbation equations demonstrates that this radiation–condensation instability can create particle clumps and voids out of a secularly cooling gas. Provided radiation can escape to cool particle overdensities, thermal instability can help assemble chondrite parent bodies out of the vaporized debris of asteroid collisions and form planetesimals generally.

The stellar masses of galaxies are measured from integrated light via several methods—however, few of these methods were designed for low-mass (M_⋆ ≲ 10⁸M_⊙) “dwarf” galaxies, whose properties (e.g., stochastic star formation, low metallicity) pose unique challenges for estimating stellar masses. In this work, we quantify the precision and accuracy at which stellar masses of low-mass galaxies can be recovered using UV/optical/IR photometry. We use mock observations of 469 low-mass galaxies from a variety of models, including both semi-empirical models (GRUMPY and UniverseMachine-SAGA) and cosmological baryonic zoom-in simulations (MARVELous Dwarfs and FIRE-2), to test literature color–M_⋆/L relations and multiwavelength spectral energy distribution (SED) mass estimators. We identify a list of “best practices” for measuring stellar masses of low-mass galaxies from integrated photometry. We find that literature color–M_⋆/L relations are often unable to capture the bursty star formation histories (SFHs) of low-mass galaxies, and we develop an updated prescription for stellar mass based on g − r color that is better able to recover stellar masses for the bursty low-mass galaxies in our sample (with ∼0.1 dex precision). SED fitting can also precisely recover stellar masses of low-mass galaxies, but this requires thoughtful choices about the form of the assumed SFH: Parametric SFHs can underestimate stellar mass by as much as ∼0.4 dex, while nonparametric SFHs recover true stellar masses with insignificant offset (−0.03 ± 0.11 dex). Finally, we also caution that noninformative (wide) dust attenuation priors may introduce M_⋆ uncertainties of up to ∼0.6 dex.

Current, realistic numerical simulations of the solar atmosphere reproduce observations in a statistical sense; they do not replicate observations such as a movie of solar granulation. Inversions on the other hand reproduce observations by design, but the resulting models are often not physically self-consistent. Physics-informed neural networks (PINNs) offer a new approach to solving the time-dependent radiative hydrodynamics equations and matching observations as boundary conditions. PINNs approximate the solution of the integro-differential equations with a deep neural network. The parameters of this network are determined by minimizing the residuals with respect to the physics equations and the observations. The resulting models are continuous in all dimensions, can zoom into local areas of interest in space and time, and provide information on physical parameters that are not necessarily directly observed such as horizontal velocities. Here, we present the first proof of concept of this novel approach, explain the underlying methodology in detail, and provide an outlook to the many applications that PINNs enable.

Chlorine–sulfur chemistry plays a significant role in the atmospheric processes of Venus, yet many aspects remain unclear, despite decades of study. This work presents a theoretical investigation into the photochemistry of ClSS and SClS isomers using high-level ab initio methods. ClSS is predicted to be the most stable isomer, exhibiting two significant absorption peaks at 384 and 243 nm. The 243 nm absorption may lead to photodissociation (yielding S, ClS, or S₂) or fluorescence back to the ground state, while absorption at 384 nm produces Cl and S₂. In contrast, SClS is predicted to be photochemically unstable. A comprehensive set of spectroscopic constants for both isomers is provided, to support future experimental detections and astronomical observations. Although atmospheric models of Venus suggest ClS₂ abundances are likely too low, the calculated spectrum of ClSS shows significant overlap with the 320–400 nm range of Venus’ enigmatic near-UV absorber. This study establishes essential spectroscopic benchmarks for ClS₂ isomers, advancing our understanding of sulfur–chlorine photochemical networks in Venus and related environments.

Spherically symmetric accretion incorporating self-gravity constitutes a three-point boundary value problem (TPBVP) governed by constraints at the outer boundary, sonic point, and accretor surface. Previous studies have two limitations: either employing an incorrect formula for self-gravity potential in analytical treatments, or introducing additional input parameters in numerical implementations to circumvent solving the full TPBVP. To address these issues, we present a self-consistent TPBVP formulation, solved using the relaxation method. We also derive approximate analytical formulae that enable rapid estimates of self-gravity effects. Our analysis identifies a dimensionless parameter that characterizes the strength of self-gravity, where and r_out are the mean density and outer radius of the flow, respectively, and a_out is the adiabatic sound speed of the external medium. For practical estimation, may be approximated by the external medium density ρ_out. We identify an upper limit for β, beyond which steady accretion becomes unsustainable—a behavior consistent with classical gravitational instability that previous studies failed to capture. The accretion rate enhancement decreases monotonically as the adiabatic index γ increases. For γ = 5/3, self-gravity ceases to augment the accretion rate. These theoretical predictions are validated by our numerical solutions. We further apply our results to two astrophysical scenarios: hyper-Eddington accretion onto supermassive black hole seeds in the early Universe, where self-gravity is significant; and accretion onto stellar-mass objects embedded in active galactic nuclei disks, where self-gravity is non-negligible under certain conditions and should be evaluated using β.

Measuring properties of young stellar objects (YSOs) is necessary for probing the pre-main-sequence evolution of stars. As YSOs exhibit complex geometry, measurement generally entails comparing observed radiation to template populations of radiative-transfer model YSO spectral energy distributions (SEDs). Due to uncertainty on the precise mechanics of star formation, the properties inferred for YSOs using these models often depend strongly on the assumed accretion history. We develop a framework for predicting observable properties of YSOs that is agnostic to the underlying accretion history, enabling comparison between theories. This framework links a set of radiative-transfer SEDs with protostellar evolutionary tracks to create models of evolving YSOs. Unlike previous works, we directly relate evolution models to observables through theoretical physical parameters rather than through intermediate, observationally derived analogs. We make flux predictions for YSOs corresponding to stars with birth masses from 0.2 to 50 M_⊙ during their accretion phase following isothermal-sphere, turbulent-core, and competitive accretion histories, showing that these histories may be observationally distinguished by examining the 100 μm and 3 mm fluxes of a YSO. We discuss the impact of dust models and parameter ranges on the output of radiative-transfer simulations through a comparison to another SED model grid. We quantify the degree of confusion between YSO Stages and Classes across a wide range of physical scenarios; for each, we calculate confusion matrices that enable inference of the number of objects of a given Stage from an observed population. Finally, we critically examine the physical significance of various literature Stage and Class definitions.

The study of local cosmic-ray (CR) sources is crucial for understanding the anomalous features observed in the energy spectra of CR nuclei, as well as the reversal of both the amplitude and phase of CR anisotropy around 100 TeV. Among the candidate sources, Geminga and Monogem are frequently considered primary contributors to the observed CR spectrum. However, the precise role of Monogem remains an open question. In this work, we conduct a detailed reanalysis of the contributions from these two local sources using a three-dimensional, spatially dependent propagation model that explicitly accounts for the halo structure of CR sources. Our findings indicate that within this framework, CRs originating from Monogem are largely prevented from reaching Earth due to obstruction by the Geminga pulsar halo. Consequently, Geminga emerges as the dominant contributor to the local CR spectrum.

Small-sized localized brightenings are an important candidate for resolving the problem of the solar atmospheric heating. They are spread over the whole solar disk and are suggested to be caused by magnetic reconnection or wave dissipation. In the chromosphere, two kinds of bright knots (propagating bright knots and stationary ones) have been reported. In this paper, we employ the data from the Solar Dynamics Observatory to study the distribution of two kinds of the bright knots in the quiet corona. To avoid the influence of active regions, we choose the data from 2020 July 20, on which no sunspot was detected in the solar disk. Based on the observations of 3 hr duration (from 00:00 UT to 03:00 UT), 815 propagating bright knots and 19,043 stationary ones are detected. The propagating bright knots have an average area of 1.5 Mm², lifetime of 51 s, and velocity of 33 km s⁻¹. For the stationary ones, the average area and lifetime are 2.0 Mm² and 367 s, respectively. The propagating knots are located in weak magnetic field regions with an average flux density of 9.0 Gauss, which is comparable with the noise level, and their number is affected by the background radiation, e.g., the stronger the radiation, the less the propagating knots. The stationary knots are located at the locations of network fields with an average flux density of 14.4 Gauss. We suggest that the propagating bright knots are excited by wave dissipation, while the stationary knots result from magnetic reconnection.

We present a new dynamical measurement of the supermassive black hole mass and intrinsic shape of the stellar halo of the massive radio galaxy NGC 315 as part of the MASSIVE survey. High signal-to-noise ratio spectra from integral-field spectrographs at the Gemini and McDonald Observatories provide stellar kinematic measurements in 304 spatial bins from the central out to 30^″. Using ∼2300 kinematic constraints, we perform triaxial stellar orbit modeling with the TriOS code and search over ∼15,000 galaxy models with a Bayesian scheme to simultaneously measure six mass and intrinsic shape parameters. NGC 315 is triaxial and highly prolate, with middle-to-long and short-to-long axis ratios of p = 0.854 and q = 0.833, and a triaxiality parameter of T = 0.89. The black hole mass inferred from our stellar kinematics is , which is higher than inferred from CO kinematics (scaled to our distance). When the seven galaxies with M_BH measurements from both stellar and CO kinematics are compared, we find an intrinsic scatter of 0.28 dex in M_BH from the two tracers and do not detect statistically significant biases between the two methods in the current data. The implied black hole shadow size (≈4.7 μas) and the relatively high millimeter flux of NGC 315 makes this galaxy a prime candidate for future horizon-size imaging studies.

The detection of very high-energy afterglow emission of the gamma-ray burst (GRB) 221009A by the Large High Altitude Air Shower Observatory (LHAASO) provides a unique opportunity to probe particle acceleration in relativistic outflows. The hard spectrum at the multi-TeV band cannot be fully explained by synchrotron-self-Compton radiation of the conventional one-zone afterglow model. In this work, we introduce a second component of relativistic electrons from stochastic acceleration via downstream turbulence of the external shock. Using a Fokker–Planck approach to model the evolution of protons and electrons, and the nonlinear feedback of turbulence damping, we show that the inverse Compton radiation of the second electron component may harden the observed spectrum above multi-TeV energy, and significantly ameliorate the fitting to the spectral evolution measured by LHAASO without violating lower-energy observations. We also discuss the potential presence of the second electron component in other GRB afterglows, which may provide a possible observational signature for future studies.

Star formation feedback can drive large-scale, multiphase galactic outflows. The dynamical and thermodynamical interaction between the hot and cooler phases is a prime focus of both observational and theoretical work. Here, we analyze Hα-emitting structures in the extraplanar wind of the nearby starburst M82. We use high-resolution, narrowband, observations from the Hubble Legacy Archive. Our analysis constrains the morphology, number density, and column density of the structures. We highlight conspicuous arc-like structures that differ significantly from the linear cometary clouds that emerge from galactic wind simulations and discuss their possible origins, such as bow shocks or instabilities driven by cosmic rays. The most prominent structures range in size from ∼24 to 110 pc. Using the Hα brightness and assumptions about the depth of the emitting structures, we estimate number densities of ∼1–23 cm⁻³ assuming a unity volume filling factor, which are lower than previous constraints from spectroscopic nebular line studies. The derived column densities, ∼10²⁰–10²¹ cm⁻², along the path of the outflow are above theoretical thresholds for cool cloud survival in a hot supersonic background, but small enough that the structures could be accelerated by the hot wind momentum. Using diffuse X-ray emission maps from Chandra, we also find that even on small (∼100 pc) scales, the Hα “leads” the X-rays, a behavior long noted in the literature on kiloparsec scales. This behavior, along with previous observational studies of ionization in the wind, may signal that shock ionization is responsible for the Hα emission we observe.

Changing-look active galactic nuclei (CL-AGNs), are AGNs that appear to transition between Seyfert Type 1 and 2 over periods of months to years. Several mechanisms to trigger these transitions have been proposed, but we have yet to conclusively determine their cause. Recent studies suggest CL-AGNs are hosted primarily in galaxies that are shutting down star formation (S. A. Dodd et al. 2021; W.-J. Liu et al. 2021; J. Wang et al. 2023), which may indicate a link between galaxy quenching and changing-look events. We use Prospector stellar population synthesis software (B. Johnson & J. Leja 2017; J. Leja et al. 2017; B. D. Johnson et al. 2021) to model nonparametric star formation histories for 39 CL-AGN host galaxies. We find that of our gold sample CL-AGNs at z < 0.15 are star-forming, while fall in the Green Valley of the stellar mass–specific star formation rate diagram. At z > 0.15, of CL-AGNs in the gold sample are star-forming and are in the Green Valley. CL-AGN hosts have similar star formation properties to the host galaxies of Seyfert 1 and 2 AGNs at z < 0.15 and to Seyfert 2 AGNs at z > 0.15. We find no statistically significant differences in the star formation properties of turn-on and turn-off CL-AGNs. We also find no evidence for rapid quenching in the Green Valley CL-AGNs. We conclude that CL-AGN state transitions are not associated with the formation history of CL-AGN host galaxies on large spatial scales, implying CL-AGN state transitions may instead result from nuclear-scale or accretion disk effects.

Changing-look quasars (CLQs) challenge many models of the quasar central engine. Their extreme variability in both the continuum and broad emission-line fluxes on timescales on the order of years is difficult to explain. To investigate the cause of the observed transitions, we present new contemporaneous optical and X-ray observations of three faded CLQs as they return to a state of high optical luminosity. Two of these three remained in a quiescent state for more than 10 yr before returning to a new high state. We find that before, during, and after transition, the spectral energy distributions of all three follow predictions for quasars based on X-ray binary outbursts, suggesting that the underlying mechanism is likely a changing accretion rate causing changes in the accretion flow structure. In two of the three cases, the transition between the initial high and low state and the transition between the low and new high state took nearly identical amounts of time, on the order of hundreds of days. This transition timescale is a useful constraint on models of the accretion state changes. The behavior of the broad emission-line profiles suggests that the broad-line region structure is changing during the transition.

Observations and theory suggest that Type Ia supernovae (SNIa) heating and mass loss from asymptotic giant branch (AGB) stars play a crucial role in the interstellar medium (ISM) of massive galaxies. We perform 3D hydrodynamic simulations of the central few kiloparsecs of massive galaxies, including radiative cooling and mass and energy injection from AGB winds and SNIa (resolving each SNIa remnant, a few ×10 pc in size), excluding black hole feedback. We study systems with different initial core thermodynamic profiles, focusing on NGC 1399. Our fiducial simulation reproduces its observed density and entropy profiles well. Over 100 Myr, two steady-state profiles emerge, depending on the inner circumgalactic medium (CGM) pressure and the ratio of Ia heating to cooling: (i) if SNIa heating is less than cooling, a cooling flow develops; (ii) if SNIa heating is comparable to or exceeds cooling, SNIa heating drives a slow subsonic outflow of AGB ejecta, with black hole accretion at small radii. This outflow, pressure-confined by the CGM, adapts the ISM to the CGM properties: a low-entropy CGM results in a dense, low-entropy ISM with higher black hole accretion, while a high-entropy CGM leads to a less dense, high-entropy ISM with lower accretion. This suggests that the AGB-SNIa-regulated ISM connects CGM and galaxy scales, potentially influencing black hole feedback in massive halos. Approximate methods of modeling Ia heating, such as clustered SNIa and smoothly distributed heating, produce unrealistic ISM profiles over 100 Myr, highlighting the importance of resolving SNIa in simulations.

Using the Bayesian Analysis of Stellar Evolution-9 code and Gaia DR3, Pan-STARRS, and 2MASS data, we identify photometric binaries in 35 open clusters (OCs) and constrain their masses. We find a strong correlation between the binary fraction and cluster dynamical age and an even stronger correlation between core binary fraction and cluster dynamical age. We find that the binary mass-ratio (q) distribution of dynamically young OCs is statistically distinct from that of the old OCs. On average, dynamically young OCs display multimodal q distributions rising toward unity and toward our detection limit of q = 0.5 while more dynamically evolved clusters display more uniform q distributions, often with a peak near q = 1. Interestingly, the uniform q distribution with a peak near q = 1 is consistent with binaries in the field. We also observe a similar transition from multimodal to unimodal q distributions when comparing low-mass to high-mass OCs in our sample. Finally, we find a correlation between the median q of the binary population in a cluster and the cluster dynamical age. We interpret these results as an indication that dynamical encounters tend to increase the fraction of high-mass-ratio binaries within a given cluster—in particular within the cluster’s core, where stellar dynamics are likely more important. This may be the result of stellar exchanges that tend to produce binaries with larger q and/or the preferential disruption or evaporation of lower-q binaries.

Studying compact object binary mergers in star clusters is crucial for understanding stellar evolution and dynamical interactions in galaxies. Open clusters in particular are more abundant over cosmic time than globular clusters. However, previous research on low-mass clusters with ≲10³M_⊙ has focused on binary black holes (BBHs) or black hole–neutron star (BH–NS) binaries. Binary mergers of other compact objects, such as white dwarfs (WDs), are also crucial as progenitors of transient phenomena such as Type Ia supernovae and fast radio bursts (FRBs). We present simulations of three types of open clusters with masses of 10², 10³, and 10⁴ M_⊙. In massive clusters with ≳10⁴ M_⊙, BBHs are dynamically formed; however, less massive compact binaries such as WD–WDs and WD–NSs are perturbed inside the star clusters, causing them to evolve into other objects. We further find BH–NS mergers only in 10³ M_⊙ clusters. Considering star clusters with a typical open cluster mass, we observe that WD–WD merger rates slightly increase for 10³ M_⊙clusters but decrease for 10² M_⊙ clusters. Since the host clusters are tidally disrupted, most of them merge outside of the clusters. Our WD–WD merger results have further implications for two classes of transients. Super-Chandrasekhar WD–WD mergers are present in our simulations, demonstrating potential sources of FRBs at a rate of 70–780 Gpc⁻³ yr⁻¹, higher than the rate estimated for globular clusters. Additionally, we find that carbon–oxygen WD–WD mergers in our open clusters (34–640 Gpc⁻³ yr⁻¹) only account for 0.14%–2.6% of the observed Type Ia supernova rate in our local Universe.

We present a comprehensive timing analysis of X-ray data from the XMM-Newton satellite, examining 50 light curves covering 17 yr of observations of the blazar Mrk 421. This work uses classical deterministic and stochastic methods in a novel way, enabling the distinction of temporal scales and offering essential insights through correlations among parameters. Deterministic behaviors are primarily explored through recurrence quantification analysis, used innovatively by varying the threshold input parameter to examine variability at multiple temporal scales. To investigate the behavior across various scales from a stochastic perspective, we apply both autoregressive moving average and autoregressive integrated moving average (ARIMA) models, with the results from ARIMA being more tightly related to short scales. Our findings reveal that Mrk 421’s X-ray emission is a multifaceted process, driven by both deterministic and stochastic patterns, indicating a complex interplay of physical phenomena. Our study demonstrates that deterministic patterns are more pronounced at small temporal scales, which are disconnected from large scales. On the other hand, stochastic processes with memory propagate from large to small timescales, while noise affects both scales, as indicated by the correlation analysis. These results underscore the importance of using advanced methodologies for interpreting astrophysical data, contributing to ongoing discussions in blazar physics by exploring connections between our calculated parameters and established models. The same approach can potentially be applied to other sources, enhancing our general understanding of the variability and emission mechanisms in blazars.

Galaxies are predicted to assemble their stellar haloes through the accretion of stellar material from interactions with their cosmic environment. Observations that trace stellar halo buildup probe the processes that drive galaxy size and stellar mass growth. We investigate stellar halo assembly over 0.2 ≤ z ≤ 1.1 in a mass-complete (M_⋆ ≥ 10^9.5M_⊙) sample of 242,456 star-forming galaxies (SFGs) and 88,421 quiescent galaxies (QGs) from the CLAUDS and HSC-SSP surveys. We extract galaxy rest-frame g-band surface brightness (μ_g) profiles to study faint, extended emission in galaxy outskirts. We examine trends in galaxy assembly by analyzing the median μ_g profiles in different SFG and QG M_⋆ ranges with decreasing redshift and connecting evolution in galaxy μ_g profiles with the underlying stellar mass growth in galaxies. Since z = 1.1, the majority of evolution in the median μ_g profiles of galaxies (∼64% in SFGs and ∼71% in QGs) occurs throughout their stellar halo regions (2–10 R_e). More-massive galaxies assemble stellar halo material more rapidly at 0.2 ≤ z ≤ 1.1. Over this period, QGs grow a larger fraction of their stellar haloes than SFGs at fixed M_⋆ (factor of ∼1.2). Although star formation can account for the stellar halo growth observed in low-mass SFGs (10^9.5M_⊙ ≤ M_⋆ < 10^10.5M_⊙), high-mass SFGs (M_⋆ ≥ 10^10.5M_⊙), and both low- and high-mass QGs require an additional assembly mechanism. Our results suggest accretion via minor mergers drives additional stellar halo growth in these galaxies. The contribution from accretion is larger in more-massive galaxies (over M_⋆ ≥ 10^9.5M_⊙), and QGs exhibit larger fractional increases to their ex situ fractions over 0.2 ≤ z ≤ 1.1 than SFGs at fixed M_⋆.

We investigate the impact of geometric corrections to the Bondi–Hoyle–Lyttleton (BHL) accretion scheme applied to evolving symbiotic systems. We model systems where 0.7 and 1 M_⊙ white dwarfs (WDs) accrete material from solar-like stars with initial masses of 1, 2, and 3 M_⊙. The primary star is evolved using the MESA stellar evolution code, while the orbital dynamics of the system are calculated using REBOUND. The analysis focuses on systems evolving through the red giant branch and the thermally pulsating asymptotic giant branch phases that do not experience a wind Roche lobe overflow phase. We compare three scenarios: no accretion, standard BHL accretion, and the improved wind accretion. The choice of accretion prescription critically influences the evolution of symbiotic systems. Simulations using the modified model did not reach the Chandrasekhar limit, suggesting that Type Ia supernova progenitors require accretors originating from ultramassive WDs. In contrast, the standard BHL model predicts WD growth to this limit in compact systems. This discrepancy suggests that population synthesis studies adopting the traditional BHL approach may yield inaccurate results. The revised model successfully reproduces the accretion properties of observed symbiotic systems and predicts transitions between different accretion regimes driven by donor mass-loss variability. These results emphasize the need for updated wind accretion models to accurately describe the evolution of symbiotic binaries.

In the standard model of terrestrial planet formation, planets are formed through giant impacts of planetary embryos after the dispersal of the protoplanetary gas disk. Traditionally, N-body simulations have been used to investigate this process. However, they are computationally too expensive to generate sufficient planetary populations for statistical comparisons with observational data. A previous study introduced a semi-analytical model that incorporates the orbital and accretionary evolution of planets due to giant impacts and gravitational scattering. This model succeeded in reproducing the statistical features of planets in N-body simulations near 1 au around solar-mass stars. However, this model is not applicable to close-in regions (around 0.1 au) or low-mass stars because the dynamical evolution of planetary systems depends on the orbital radius and stellar mass. This study presents a new semi-analytical model applicable to close-in orbits around stars of various masses, validated through comparison with N-body simulations. The model accurately predicts the final distributions of planetary mass, semimajor axis, and eccentricity for wide ranges of orbital radius, initial planetary mass, and stellar mass, with significantly reduced computation time compared to N-body simulations. By integrating this model with other planet-forming processes, a computationally low-cost planetary population synthesis model can be developed.

An increasing number of pulsar wind nebulae (PWNe) are being identified in the TeV band by ground-based Imaging Air Cherenkov Telescopes such that they constitute the dominant source class of Galactic TeV emitters. However, MeV–GeV PWN counterparts are still largely lacking. To date, only a dozen PWNe are identified by the Fermi–Large Area Telescope (LAT) in the MeV–GeV band. Most PWNe are located along the Galactic plane embedded within the prominent, diffuse Galactic γ-ray emission, which makes these sources difficult to disentangle from the bright diffuse background. We present a systematic search for γ-ray counterparts to known PWNe in the 300 MeV–2 TeV energy band using the Fermi–LAT. We target the locations of previously identified PWNe that lack detected Fermi–LAT pulsars to minimize associated pulsar contamination. The sample includes six previously identified Fermi PWNe and eight Fermi–LAT sources associated with PWNe. We report the analysis of 58 regions of interest and classify Fermi–LAT detected sources as either a likely PWN or a candidate PWN counterpart based on their morphological and spectral characteristics across the broadband spectrum. There are nine unidentified Fermi–LAT sources that we consider as likely PWN counterparts, which, if confirmed to be PWNe, would greatly increase the PWN population detected by the Fermi–LAT from 12 to 21. The remaining Fermi–LAT detected sources are considered weaker PWN candidates. A second approach in the systematic search for γ-ray emitting PWNe will involve studying the off-pulse phases of Fermi–LAT detected pulsars for the presence of an obscured PWN and will be reported in a subsequent paper.

A planet’s axial tilt (“obliquity”) substantially affects its atmosphere and habitability. It is thus essential to comprehend the various mechanisms that can excite planetary obliquities, particularly at the primordial stage. Here, we explore planetary obliquity excitation induced by the early evolution of the host star. A young, distended star spins rapidly, resulting in a large gravitational quadrupole moment that induces nodal recession of the planet’s orbit. As the star contracts and spins down, the nodal recession frequency decreases and can cross the planet’s spin axis precession frequency. An adiabatic encounter results in the planet’s capture into a secular spin–orbit resonance and excites the obliquity to large values. We find that planets within a ≲ 1 au are most affected, but adiabatic capture depends on the initial stellar radius and spin rate. The overall picture is complicated by other sources of perturbation, including the disk, multiple planets, and tidal dissipation. Tides make it such that stellar oblateness-induced obliquity excitation is transient since tidal perturbations cause the resonance to break once high obliquities are reached. However, this early transient excitation is important because it can prime planets for long-term capture in a secular spin–orbit resonance induced by planet–planet interactions. Thus, although stellar oblateness-induced resonances are short-lived, they facilitate the prevalence of long-lived nonzero obliquities in exoplanets.

Dual active galactic nuclei (AGNs), a phase in some galaxy mergers during which both central supermassive black holes (SMBHs) are active, are expected to be a key observable stage leading up to SMBH mergers. Constraining the population of dual AGNs in both the nearby and high-z Universe has proven to be elusive until very recently. We present a multiwavelength follow-up campaign to confirm the nature of a sample of 20 candidate dual AGNs at cosmic noon (z ∼ 2) from the VODKA sample. Through a combination of Hubble Space Telescope and Very Large Array imaging, we refute the possibility of gravitational lensing in all but one target. We find evidence of dual AGNs in three systems, while seven exhibit a single AGN in galaxy pairs, through either strong radio emission or ancillary emission-line data. The remaining systems are confirmed as either quasar−star superpositions (seven) or nonlensed pairs (two) that require further investigations to establish AGN activity. Among the systems with radio detections, we find a variety of radio spectral slopes and UV/optical colors suggesting that our sample contains a range of AGN properties, from obscured radio-quiet objects to those with powerful synchrotron-emitting jets. This study presents one of the largest dedicated multiwavelength follow-up campaigns to date searching for dual AGNs at high redshift. We confirm several of the highest-z systems at small physical separations, thus representing some of the most evolved dual-AGN systems at the epoch of peak quasar activity known to date.

Gamma-ray bursts (GRBs) are the most energetic phenomena in the Universe, characterized by prompt gamma-ray emission followed by multiwavelength afterglows. X-ray flares, observed during the afterglow phase, are generally believed to originate from the prolonged activity of the central engine, though direct evidence has been scarce. In this study, we present a comprehensive statistical analysis of X-ray flares from 315 GRBs observed by the Swift/X-ray Telescope over nearly two decades. We categorize flares into prompt flares (occurring during the prompt emission phase) and afterglow flares and compare their temporal and luminosity properties. Our analysis reveals that both types of flares exhibit similar morphological characteristics, with prompt flares being brighter and occurring earlier than afterglow flares. We find strong correlations between flare parameters, such as peak time, duration, and luminosity, which follow consistent patterns across both flare types. These findings suggest that X-ray flares, regardless of their timing, share a common origin in the central engine’s activity. Our results imply that the central engine’s activity duration extends beyond the prompt gamma-ray emission phase, highlighting the importance of considering X-ray flares when studying GRB progenitors and central engine properties. This work provides robust statistical evidence supporting the central engine origin of X-ray flares and underscores the need for future observations with missions like the Space-based multi-band astronomical Variable Objects Monitor and Einstein Probe to further elucidate the nature of GRB central engines.

The simple stellar population models produced by stellar population and spectral synthesis (SPS) codes are used as spectral templates in a variety of astrophysical contexts. In this paper, we test the predictions of four commonly used stellar population synthesis codes (YGGDRASIL, BPASS, FSPS, and a modified form of GALAXEV, which we call GALAXEVneb) by using them as spectral templates for photometric spectral energy distribution (SED) fitting with a sample of 18 young stellar clusters. All clusters have existing Hubble Space Telescope (HST) Cosmic Origins Spectrograph far-UV spectroscopy that provides constraints on their ages as well as broadband photometry from HST Advanced Camera for Surveys and Wide Field Camera 3. We use model spectra that account for both nebular and stellar emission, and additionally test four extinction curves at different values of R_V. We find that for individual clusters, choice of extinction curve and SPS model can introduce significant scatter into the results of SED fitting. Model choice can introduce scatter of 34.8 Myr in age, a factor of 9.5 in mass, and 0.40 mag in extinction. Extinction curve choice can introduce scatter of up to a factor of 32.3 Myr in age, a factor of 10.4 in mass, and 0.41 mag in extinction. We caution that because of this scatter, one-to-one comparisons between the properties of individual objects derived using different SED fitting setups may not be meaningful. However, our results also suggest that SPS model and extinction curve choice do not introduce major systematic differences into SED fitting results when the entire cluster population is considered. The distribution of cluster properties for a large enough sample is relatively robust to user choice of SPS code and extinction curve.

We present results from Atacama Large Millimeter/submillimeter Array (ALMA) spectral line-scan observations at 3 mm and 2 mm bands of three near-infrared-dark (NIR-dark) galaxies behind two massive lensing clusters MACS J0417.5-1154 and RXC J0032.1+1808. Each of these three sources is a (sub)millimeter faint (delensed S_{1.2 mm} < 1 mJy) triply lensed system originally discovered in the ALMA Lensing Cluster Survey. We have successfully detected CO and [C i] emission lines and confirmed that their spectroscopic redshifts are z = 3.652, 2.391, and 2.985. By utilizing a rich multiwavelength data set, we find that the NIR-dark galaxies are located on the star formation main sequence in the intrinsic stellar mass range of log (M_*/M_⊙) = 9.8–10.4, which is about 1 order of magnitude lower than that of typical submillimeter galaxies (SMGs). These NIR-dark galaxies show a variety in gas depletion times and spatial extent of dust emission. One of the three is a normal star-forming galaxy with gas depletion time consistent with a scaling relation, and its infrared surface brightness is an order of magnitude smaller than that of typical SMGs. Since this galaxy has an elongated axis ratio of ∼0.17, we argue that normal star-forming galaxies in an edge-on configuration can be heavily dust-obscured. This implies that existing deep WFC3/F160W surveys may miss a fraction of typical star-forming main-sequence galaxies due to their edge-on orientation.

In this work, we investigate the impact of Poisson noise from stellar-mass primordial black holes (PBHs) on the formation of ultradense dark matter halos (UDMHs). Our findings reveal that the discrete spatial distribution of PBHs significantly enhances small-scale density fluctuations, particularly for massive stellar-mass PBHs. Our results indicate that the modified power spectrum, incorporating both adiabatic and isocurvature contributions from PBH-induced Poisson noise, strongly depends on PBH mass and fraction. Specifically, increasing PBH mass shifts the differential mass function of UDMHs toward higher masses, while variations in the suppression parameter n modulate the efficiency of UDMH formation at small scales. For lower values of n, our findings show a significant boost in UDMH abundance, favoring multicomponent dark matter scenarios. Conversely, at higher values of n, the predicted UDMH distributions align more closely with single-component models dominated by stellar-mass PBHs. Furthermore, our analysis demonstrates that more realistic halo mass functions, which account for angular momentum and dynamical friction, consistently predict higher UDMH abundances compared to the traditional Press–Schechter formalism.

The standard formation model of close-in low-mass planets involves efficient inward migration followed by growth through giant impacts after the protoplanetary gas disk disperses. While detailed N-body simulations have enhanced our understanding, their high computational cost limits statistical comparisons with observations. In our previous work, we introduced a semianalytical model to track the dynamical evolution of multiple planets through gravitational scattering and giant impacts after the gas disk dispersal. Although this model successfully reproduced N-body simulation results under various initial conditions, our validation was still limited to cases with compact, equally spaced planetary systems. In this paper, we improve our model to handle more diverse planetary systems characterized by broader variations in planetary masses, semimajor axes, and orbital separations and validate it against recent planet population synthesis results. Our enhanced model accurately reproduces the mass distribution and orbital architectures of the final planetary systems. Thus, we confirm that the model can predict the outcomes of postgas disk dynamical evolution across a wide range of planetary system architectures, which is crucial for reducing the computational cost of planet formation simulations.

Electron beams accelerated in solar flares and escaping from the Sun along open magnetic field lines can trigger intense radio emissions known as type III solar radio bursts. Utilizing observations by Parker Solar Probe (PSP), STEREO-A, Solar Orbiter, and Wind spacecraft, the speeds and accelerations of type III exciters are derived for simple and isolated type III solar bursts. For the first time, simultaneous four spacecraft observations allow us to determine positions and correct the resulting velocities and accelerations for the location between the spacecraft and the apparent source. We observe velocities and acceleration to change as u(r) ∝ r^{−0.37 ± 0.14} and a(r) ∝ r^{−1.71 ± 0.20} with radial distance from the Sun r. To explain the electron beam deceleration, we develop a simple gas-dynamic description of the electron beam moving through plasma with monotonically decreasing density. The model predicts that the beam velocity decreases as u(f) ∝ f^1/4(r), so the acceleration changes ∝r^−1.58 (and speed as ∝r^−0.29) for the plasma density profile n(r) ∝ r^−2.3. The deceleration is consistent with the average observation values corrected for the type III source locations. Intriguingly, the observations also show differences in velocity and acceleration of the same type III observed by different spacecraft. We suggest the difference could be related to the additional time delay caused by radio-wave scattering between the spacecraft and the source.

Subparsec binary supermassive black holes (BSBHs) should be common from galaxy mergers, yet direct evidence has been elusive. We present Hubble Space Telescope (HST)/WFC3IR F160W imaging for a sample of eight candidate subparsec BSBHs at redshifts z ∼ 0.1–0.5, as well as cross-comparison with a sample of ordinary quasars with archival HST/WFC3 IR F160W images. These eight candidate subparsec BSBHs were identified from multiepoch spectroscopic surveys of quasars (including both typical quasars and those with single-peaked velocity-offset broad lines), whose broad Hβ lines are significantly offset (by ≳ a few hundred kilometers per second) from the systemic redshifts. We directly test the prediction that the host galaxies of BSBHs would have a higher fraction of disturbed morphologies and younger stellar bulges from recent interactions than those of control quasars. After careful subtraction of the central quasar light, our candidate BSBH hosts show a statistically undifferentiated distribution of host asymmetry, indicative of a similar fraction of recent mergers. While a significantly larger sample is needed to place this result on a much firmer statistical ground, it opens questions as to the timescale differences between galaxy merger and BSBH formation, or the efficacy of the radial-velocity-shift-based selection of subparsec BSBH candidates.

We present an assumption-minimized framework for testing late-time cosmological models using uncalibrated cosmic standards (UCS)—including standard rulers and standard candles—without relying on absolute calibrations. The method exploits a tight, model-insensitive correlation between the sound horizons at recombination and the drag epoch. By avoiding dependence on prerecombination physics and the amplitude of the cosmic microwave background (CMB) power spectra, the UCS framework reduces potential early-Universe biases while retaining much of the constraining power of full analyses. Applying UCS to the recent dynamical dark energy study that reported deviations from ΛCDM, we find the constraints shift systematically toward the ΛCDM case. If this shift is physical, it may result from the omission of some prerecombination physical processes that influence the scale dependence of the CMB spectra. We also observe a mild tension between uncalibrated standard rulers and candles, which can be largely mitigated by introducing a redshift-dependent magnitude bias in the Type Ia supernovae data. Our results highlight the importance of isolating postrecombination observables for testing late-time models in the era of precision cosmology, positioning UCS analysis as a robust framework for upcoming galaxy surveys.

The circular speed curve of the Milky Way provides a key constraint on its mass distribution, reflecting the axisymmetric component of the gravitational potential. This is especially critical in the inner Galaxy (R ≲ 4 kpc), where nonaxisymmetric structures, such as the stellar bar and nuclear stellar disk, strongly influence dynamics. However, significant discrepancies remain between circular speed curves inferred from stellar dynamical modeling and those derived from the terminal-velocity method applied to gas kinematics. To investigate this, we perform three-dimensional hydrodynamic simulations including cooling, heating, star formation, and feedback, under a realistic gravitational potential derived from stellar dynamical models calibrated to observational data. This potential includes the Galactic bar, stellar disks, dark matter halo, nuclear stellar disk, and nuclear star cluster. We generate synthetic longitude–velocity diagrams and apply the terminal-velocity method to derive circular speeds. The simulated gas reproduces the observed terminal-velocity envelope, including a steep inner rise. We find this feature arises from bar-driven noncircular motions, which cause the terminal-velocity method to overestimate circular speeds by up to a factor of 2 at R ∼ 0.4 kpc, and enclosed mass by up to a factor of 4. These results suggest that inner gas-based rotation curves can significantly overestimate central mass concentrations. The steep inner rise in gas-derived circular speeds does not require a massive classical bulge but can be explained by bar-induced streaming motions. Rather than proposing a new mechanism, our study provides a clear, Milky Way–specific demonstration of this effect, emphasizing the importance of dynamical modeling that explicitly includes noncircular motions for accurate mass inference in the inner Milky Way.

Extreme-mass-ratio inspirals (EMRIs) and intermediate-mass-ratio inspirals (IMRIs) are important gravitational wave (GW) sources for the Laser Interferometer Space Antenna. It has recently been suggested that EMRIs and IMRIs can both form in the accretion disk of an active galactic nucleus (AGN). Considering the likely encounter between a stellar-mass black hole (sBH) and an intermediate-mass black hole (IMBH) during migration in the AGN disk, P. Peng & X. Chen (Paper I) showed that a gap-opening IMBH can drive a surrounding sBH to migrate synchronously. In this work, we extend the study in Paper I with a more sophisticated model. We first use 3D hydrodynamical simulations to study the coevolution of the disk and the migration of an sBH in the vicinity of an IMBH. We find that the gaseous torque, together with the tidal torque exerted by the IMBH, can drive synchronized migration until ∼10 Schwarzschild radii from the central supermassive black hole. We further use a relativistic three-body code to study the final fate of the sBH in the GW-dominated regime. We find that the sBH can be either captured or kicked out by the IMBH, which will result in either two subsequent IMRIs or an EMRI followed by an IMRI. These events will bring rich information about the formation and evolution of sBHs and IMBHs in AGNs.

We present the analysis of the extended main-sequence turnoff (eMSTO) in the open cluster NGC 6067. We derive the projected rotational velocity, vsini, of the stars belonging to the eMSTO region of the main sequence (MS) utilizing Gaia-ESO spectra. Our results reveal a positive correlation between vsini and the color of eMSTO stars, where fast-rotating stars predominantly occupy the red part of the MS while slow-rotating ones prefer a bluer side of the MS. The gravity-darkening effect might be a reason for this correlation. We find that most of the close binaries present in the eMSTO population would be slow-rotating due to the tidal-locking phenomenon. We identify four double-lined spectroscopic binaries (SB2) featuring slow-rotating companions, further supporting this tidal-locking hypothesis. However, the spatial distribution and the cumulative radial distribution indicate a higher concentration of red eMSTO stars in the cluster’s central region than their bluer counterparts. This suggests that tidal locking is less likely to be the cause of the observed spread in rotation rates among eMSTO stars. Instead, we propose that star–disk interactions during the pre-main-sequence phase might have played a crucial role in spreading the rotation rates of stars, leading to the eMSTO phenomenon in NGC 6067.

Fast radio bursts (FRBs) have emerged as one of the most dynamic areas of research in astronomy and cosmology. Despite increasing number of FRBs having been reported, the exact origin of FRBs remains elusive. Investigating the intrinsic redshift distributions of FRBs could provide valuable insights into their possible origins and enhance the power of FRBs as a cosmological probe. In this paper, we propose a hierarchical Bayesian inference approach combining with several viable models to investigate the redshift distribution of the Canadian Hydrogen Intensity Mapping Experiment/FRB catalog 1. By utilizing this method, we aim to uncover the underlying patterns and characteristics of the FRB population, i.e., the intrinsic redshift distribution of FRB. Taking uncertainties within the observational data and selection effects into consideration, we found that the redshift distribution of FRBs is significantly delayed with respect to that of the star formation history.

We report the results of our long-term multiwavelength spectral energy distribution (SED) study on the flat-spectrum radio quasar 3C 279 during the ∼14 yr (2008–2022) Fermi-Large Area Telescope (LAT) observing period. The Fermi-LAT data were complemented with data in other wave bands obtained from the Swift-X-Ray Telescope (XRT)/UVOT, the Whole Earth Blazar Telescope, along with other optical and radio data from several observatories. Different activity states were identified from the weekly binned γ-ray light curve, and it was possible to create 168 high-quality and quasi-simultaneous broadband SEDs. We modeled the SEDs using a one-zone leptonic scenario, including the emission region outside the broad-line region (BLR), involving synchrotron, synchrotron self-Compton, and external Compton mechanisms. Such extensive broadband modeling is essential for constraining the underlying multiwavelength radiative mechanisms in the 3C 279 jet and permits the estimation of the physical parameters and exploration of their evolution in time. Our SED modeling study suggests that the increase in the Doppler beaming factor, along with the variation of the emitting electrons, is the cause for the flares in this source. The multiwavelength emission of 3C 279 was found to be well explained by the scenario in which the emission region is outside the BLR at a distance of ∼6.42 × 10³R_S. However, for two of the very bright γ-ray states, the emission region was found to be close to the outer boundary of the BLR at a distance of ∼1.28 × 10³R_S from the central black hole.

Fast radio bursts (FRBs) are millisecond-duration extragalactic transients characterized by ultrahigh brightness temperatures, suggesting coherent emission mechanisms in extreme astrophysical processes. In this paper, we extend the bunched coherent Cherenkov radiation (CChR) framework by incorporating bunch inclination and geometric configuration parameters, enabling it to more rigorously model FRB emission and tera-Hertz (THz) emission from magnetars. When relativistic bunches are injected into the magnetized plasma of a magnetar’s magnetosphere at the Cherenkov angle, their emitted waves achieve phase coherence through constructive interference. Furthermore, the three-dimensional geometry of the bunches plays a crucial role in influencing the coherence of the radiation. Within the framework of CChR, we predict the existence of THz emission counterparts associated with FRBs and explain the observed characteristics of the THz-emitting magnetar SGR J1745-2900. Detections of such counterparts by upgraded millimeter telescopes (e.g., Atacama Large Millimeter/submillimeter Array, IRAM) would be expected to provide new insights into the potential physical connection between FRBs and magnetars.

We have carried out a detailed analysis of PSR J1735−0243 with the Five-hundred-meter Aperture Spherical radio Telescope at 1250 MHz. We found that this pulsar shows obvious mode changing, with approximately 82% in the normal mode and approximately 18% in the abnormal mode. The two modes differ not only in their integrated pulse profiles but also in their polarization properties. Further analyses suggest that the emission from the normal mode may originate from a higher height than the abnormal mode. Additionally, we found that the radio emission beam consists of four emission components, including a core component and three cone components. The tertiary cone component, which has the highest emission height, is present in both emission modes. Finally, the results shown that the radio emission of PSR J1735−0243 may have been generated in the core gap region.

Recent studies of galaxy clusters found peculiar cases at the boundary between noncool core and cool core systems. While unusual, these objects can help us understand the evolution of the most massive clusters. We investigated the role of active galactic nucleus (AGN) feedback in the starburst brightest cluster galaxy (BCG) of the merging cool core cluster CHIPS 1911+4455 (z = 0.485). We conducted new multifrequency (0.3–5 GHz) Very Long Baseline Array (VLBA) and Jansky Very Large Array (JVLA) observations of CHIPS 1911+4455 across a wide range of scales (0.01–20 kpc). Our analysis reveals that the AGN in the BCG has recently awakened, showing a compact core with symmetric, ∼30 pc long jets in VLBA data. The onset of the AGN may be linked to the enhanced cooling of the hot gas found in a previous study. At larger scales (10 kpc), faint radio whiskers extending to the south show a striking alignment with star-forming knots and are thus interpreted as synchrotron-emitting regions associated with the starburst BCG. The implied radio star formation rate of 100–155 M_⊙ yr⁻¹ agrees with the optical/infrared one (140−190 M_⊙ yr⁻¹). Our JVLA and VLBA radio study, informed by previous X-ray/optical/millimeter works, indicates that CHIPS 1911+4455 represents a transitional phase in cluster evolution, where the AGN in the central galaxy has just begun to respond to copious hot gas cooling.

Slow magnetoacoustic waves with a 3 minute period are upward-propagating waves traveling through the density-stratified umbral atmosphere. The decreasing density causes their amplitude to increase, developing into nonlinear waves through steepening and eventually forming shocks. To investigate the vertical evolution of this wave nonlinearity, we utilized multiwavelength data from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory, covering from the photosphere to the lower corona across 20 active regions. The steepening of the wave profile leads to the generation of higher harmonics. We quantify this using a nonlinearity index (NI), defined as the ratio of the amplitude of the second harmonic to the fundamental obtained using wavelet analysis. We find a characteristic pattern: nonlinearity increases from the photosphere through the lower chromosphere, peaking near the AIA 1700 Å formation height, and decreases at higher altitudes, notably in the AIA 304 Å channel. This trend indicates progressive wave steepening and subsequent energy dissipation before reaching the formation of AIA 304 Å, consistent with shock formation in the lower atmosphere. An additional rise in NI is observed at the AIA 131 Å channel, followed by a decline in AIA 171 Å, suggesting a second phase of wave nonlinearity evolution in the lower corona. Based on the NI profile and the formation heights of these channels, we conjecture that nonlinear wave processes are most prominent between the AIA 1700 Å and AIA 304 Å formation layers and again between AIA 131 Å and AIA 171 Å.