Table of contents for issue 1, volume 933, The Astrophysical Journal

Cook et al. found that iron meteorites have an initial abundance ratio of the short-lived isotope ⁶⁰Fe to the stable isotope ⁵⁶Fe of ⁶⁰Fe/⁵⁶Fe ∼ (6.4 ± 2.0) × 10⁻⁷. This appears to require the injection of live ⁶⁰Fe from a Type II supernova (SN II) into the presolar molecular cloud core, as the observed ratio is over a factor of 10 times higher than would be expected to be found in the ambient interstellar medium (ISM) as a result of galactic chemical evolution. The supernova triggering and injection scenario offers a ready explanation for an elevated initial ⁶⁰Fe level, and in addition provides a physical mechanism for explaining the noncarbonaceous–carbonaceous (NC–CC) dichotomy of meteorites. The NC–CC scenario hypothesizes the solar nebula first accreted material that was enriched in supernova-derived nuclides, and then later accreted material depleted in supernova-derived nuclides. While the NC–CC dichotomy refers to stable nuclides, not short-lived isotopes like ⁶⁰Fe, the SN II triggering hypothesis provides an explanation for the otherwise unexplained change in nuclides being accreted by the solar nebula. Three-dimensional hydrodynamical models of SN II shock-triggered collapse show that after triggering collapse of the presolar cloud core, the shock front sweeps away the local ISM while accelerating the resulting protostar/disk to a speed of several kilometers per second, sufficient for the protostar/disk system to encounter within ∼1 Myr the more distant regions of a giant molecular cloud complex that might be expected to have a depleted inventory of supernova-derived nuclides.

The analysis of the photospheric velocity field is essential for understanding plasma turbulence in the solar surface, which may be responsible for driving processes such as magnetic reconnection, flares, wave propagation, particle acceleration, and coronal heating. Currently, the only available methods to estimate velocities at the solar photosphere transverse to an observer’s line of sight infer flows from differences in image structure in successive observations. Due to data noise, algorithms such as local correlation tracking may lead to a vector field with wide gaps where no velocity vectors are provided. In this paper, a novel method for image inpainting of highly corrupted data is proposed and applied to the restoration of horizontal velocity fields in the solar photosphere. The restored velocity field preserves all the vector field components present in the original field. The method shows robustness when applied to both simulated and observational data.

The effects of spontaneous fission on r-process nucleosynthesis are investigated in the hot wind r-process scenario. We perform network calculations using three sets of spontaneous fission rates to study how the abundance pattern is shaped when different sets of fissioning nuclei are encountered by the r-process nuclear flow. The relative contributions from spontaneous fission, neutron-induced fission, and β-delayed fission to the nucleosynthesis process are studied by calculating the corresponding fission flow. We show that the relative contributions of various fission channels in r-process nucleosynthesis depend on the astrophysical conditions and fission models used. By using the spontaneous fission rates from a modified Swiatecki’s formula with isospin and blocking effects, the spontaneous fission and neutron-induced fission play an equally important role in r-process nucleosynthesis under an extreme neutron-rich astrophysical scenario with Y_e = 0.1. The fissioning nuclei are located in different regions of the nuclear chart when different spontaneous fission models are used. The fission fragment distributions of fissioning nuclei in different regions have apparent diversity, which affects the mass regions where fission products are deposited, leading to the difference of the final abundance around the second r-process peak and rare-earth subpeak.

Using the Five-hundred-meter Aperture Spherical radio Telescope in Guizhou, China, we detect the 21 cm neutral atomic hydrogen absorption in the young planetary nebula IC 4997. The absorption arises from a shell that is also associated with Na i D lines. The H i shell has a mass of 1.46 × 10⁻²M_⊙ and a dynamic age of 990 yr. The column density of H i is estimated to be 7.1 × 10²⁰ cm⁻², which can be well explained in terms of a photodissociation region around the ionized nebula, limited by the self-shielding of H₂. We find that the atomic-to-ionized hydrogen ratio is 0.6, suggesting that H i substantially contributes to the overall nebular mass.

Massive-star binaries are critical laboratories for measuring masses and stellar wind mass-loss rates. A major challenge is inferring viewing inclination and extracting information about the colliding-wind interaction (CWI) region. Polarimetric variability from electron scattering in the highly ionized winds provides important diagnostic information about system geometry. We combine for the first time the well-known generalized treatment of Brown et al. for variable polarization from binaries with the semianalytic solution for the geometry and surface density CWI shock interface between the winds based on Cantó et al. Our calculations include some simplifications in the form of inverse-square law wind densities and the assumption of axisymmetry, but in so doing they arrive at several robust conclusions. One is that when the winds are nearly equal (e.g., O+O binaries) the polarization has a relatively mild decline with binary separation. Another is that despite Thomson scattering being a gray opacity, the continuum polarization can show chromatic effects at ultraviolet wavelengths but will be mostly constant at longer wavelengths. Finally, when one wind dominates the other, as, for example, in WR+OB binaries, the polarization is expected to be larger at wavelengths where the OB component is more luminous and generally smaller at wavelengths where the WR component is more luminous. This behavior arises because, from the perspective of the WR star, the distortion of the scattering envelope from spherical is a minor perturbation situated far from the WR star. By contrast, the polarization contribution from the OB star is dominated by the geometry of the CWI shock.

Biosignature gas research has been growing in recent years thanks to next-generation space- and ground-based telescopes. Methanol (CH₃OH) has many advantages as a biosignature gas candidate. First, CH₃OH’s hydroxyl group (OH) has a unique spectral feature not present in other anticipated gases in the atmospheres of rocky exoplanets. Second, there are no significant known abiotic CH₃OH sources on terrestrial planets in the solar system. Third, life on Earth produces CH₃OH in large quantities. However, despite CH₃OH’s advantages, we consider it a poor biosignature gas in the atmospheres of terrestrial exoplanets due to the enormous production flux required to reach its detection limit. CH₃OH’s high water solubility makes it very difficult to accumulate in the atmosphere. For the highly favorable planetary scenario of an exoplanet with an H₂-dominated atmosphere orbiting an M5V dwarf star, we find that only when the column-averaged mixing ratio of CH₃OH reaches at least 10 ppm can we detect it with the James Webb Space Telescope (JWST). The CH₃OH bioproduction flux required to reach the JWST detection threshold of 10 ppm must be of the order of 10¹⁴ molecules cm⁻² s⁻¹, which is roughly three times the annual O₂ production on Earth. Considering that such an enormous flux of CH₃OH is essentially a massive waste of organic carbon—a major building block of life, we think this flux, while mathematically possible, is likely biologically unattainable. Although CH₃OH can theoretically accumulate on exoplanets with CO₂- or N₂-dominated atmospheres, such planets’ small atmospheric scale heights and weak atmospheric signals put them out of reach for near-term observations.

By assuming the photosphere located at the outmost edge of the ejecta, Arnett et al. (1980, 1982, 1989) presented the light curves of homologous explosions in supernovae analytically and numerically to include recombination effects. Actually as homologous expansion proceeds, the photosphere recedes deeper into the ejecta. In this situation, the photosphere radius increases at early times and decreases later on, which can be described by a simple method proposed by Liu et al. To study how the photosphere recession affects the luminosity evolution, we impose a boundary condition on the photosphere to determine the spatial and time distribution of the temperature of the ejecta, which is clarified to be reasonable. We find that the photosphere recession reduces the luminosity compared with the previous result without the recession, which can be tested with observations of Type-IIP supernovae.

An infrared L- and M-band spectral survey, performed toward the young planetary nebula NGC 7027 with the iSHELL instrument on NASA’s Infrared Telescope Facility (IRTF), has revealed more than 20 vibrational lines of the molecules HeH⁺, H₂, and CH⁺ and more than 50 spectral lines of atoms and atomic ions. The present paper focuses on the atomic line emissions, the molecular lines having been discussed in two previous publications. The atomic lines detected with high confidence in the 2.951–5.24 μm region covered (incompletely) by this survey comprise (1) six collisionally excited lines of metal ions that had previously been identified in astrophysical nebulae but for which the present observations provide the most accurate wavelength determinations obtained to date; (2) a spectral line at 4.6895 μm, not previously reported, for which the probable identification is the ⁴F_7/2–⁴F_9/2 fine-structure transition of [Zn vi]; (3) 39 recombination lines of H and He⁺, with upper states of principal quantum number up to 38 (H) or 24 (He⁺); (4) 10 recombination lines of the multielectron species He, C²⁺, and C³⁺.

Using the extended halo-based group finder developed by Yang et al., which is able to deal with galaxies via spectroscopic and photometric redshifts simultaneously, we construct galaxy group and candidate protocluster catalogs in a wide redshift range (0 < z < 6) from the joint CFHT Large Area U-band Deep Survey and Hyper Suprime-Cam Subaru Strategic Program deep data set. Based on a selection of 5,607,052 galaxies with i-band magnitude m_i < 26 and a sky coverage of 34.41 deg², we identify a total of 2,232,134 groups, of which 402,947 groups have at least three member galaxies. We have visually checked and discussed the general properties of these richest groups at redshift z > 2.0. By checking the galaxy number distributions within a 5–7 h⁻¹Mpc projected separation and a redshift difference Δz ≤ 0.1 around those richest groups at redshift z > 2, we identify lists of 761, 343, and 43 protocluster candidates in the redshift bins 2 ≤ z < 3, 3 ≤ z < 4, and z ≥ 4, respectively. In general, these catalogs of galaxy groups and protocluster candidates will provide useful environmental information in probing galaxy evolution along cosmic time.

In this VERTICO early science paper we explore in detail how environmental mechanisms, identified in H i, affect the resolved properties of molecular gas reservoirs in cluster galaxies. The molecular gas is probed using ALMA ACA (+TP) observations of ¹²CO(2–1) in 51 spiral galaxies in the Virgo cluster (of which 49 are detected), all of which are included in the VIVA H i survey. The sample spans a stellar mass range of . We study molecular gas radial profiles, isodensity radii, and surface densities as a function of galaxy H i deficiency and morphology. There is a weak correlation between global H i and H₂ deficiencies, and resolved properties of molecular gas correlate with H i deficiency: galaxies that have large H i deficiencies have relatively steep and truncated molecular gas radial profiles, which is due to the removal of low-surface-density molecular gas on the outskirts. Therefore, while the environmental mechanisms observed in H i also affect molecular gas reservoirs, there is only a moderate reduction of the total amount of molecular gas.

We present new Atacama Large Millimeter/submillimeter Array (ALMA) results obtained from spatially resolved CO J = 2–1 line (04 resolution) and 870 μm continuum (02 resolution) observations of cluster galaxies in XMMXCS J2215.9-1738 at z = 1.46. Our sample comprises 17 galaxies within ∼0.5 Mpc (0.6R₂₀₀) of the cluster center, all of which have previously been detected in the CO J = 2–1 line at a lower resolution. The effective radii of both the CO J = 2–1 line and 870 μm dust continuum emissions are robustly measured for nine galaxies by modeling the visibilities. We find that the CO J = 2–1 line emission in all of the nine galaxies is more extended than the dust continuum emission by a factor of 2.8 ± 1.4. We investigate the spatially resolved Kennicutt–Schmidt (KS) relation in two regions within the interstellar medium of the galaxies. The relation for our sample reveals that the central region (0 < r < R_e,870μm) of galaxies tends to have a shorter gas depletion timescale, i.e., a higher star formation efficiency, compared to the extended region (R_e,870μm < r < R_e,CO). Overall, our result suggests that star formation activities are concentrated inside the extended gas reservoir, possibly resulting in the formation of a bulge structure. We find consistency between the ALMA 870 μm radii of star-forming members and the Hubble Space Telescope/1.6 μm radii of passive members in a mass–size distribution, which suggests a transition from star-forming to passive members within ∼0.5 Gyr. In addition, no clear differences in the KS relation nor in the sizes are found between galaxies with and without a close companion.

We examine the cradle-to-grave magnetic evolution of 10 bipolar ephemeral active regions (BEARs) in solar coronal holes, especially aspects of the magnetic evolution leading to each of 43 obvious microflare events. The data are from the Solar Dynamics Observatory: 211 Å coronal EUV images and line-of-sight photospheric magnetograms. We find evidence that (1) each microflare event is a magnetic explosion that results in a miniature flare arcade astride the polarity inversion line (PIL) of the explosive lobe of the BEAR’s anemone magnetic field; (2) relative to the BEAR’s emerged flux-rope Ω loop, the anemone’s explosive lobe can be an inside lobe, an outside lobe, or an inside-and-outside lobe; (3) 5 events are confined explosions, 20 events are mostly confined explosions, and 18 events are blowout explosions, which are miniatures of the magnetic explosions that make coronal mass ejections (CMEs); (4) contrary to the expectation of Moore et al., none of the 18 blowout events explode from inside the BEAR’s Ω loop during the Ω loop’s emergence; and (5) before and during each of the 43 microflare events, there is magnetic flux cancellation at the PIL of the anemone’s explosive lobe. From finding evident flux cancellation at the underlying PIL before and during all 43 microflare events—together with BEARs evidently being miniatures of all larger solar bipolar active regions—we expect that in essentially the same way, flux cancellation in sunspot active regions prepares and triggers the magnetic explosions for many major flares and CMEs.

The Disk Detective citizen science project recently released a new catalog of disk candidates found by visual inspection of images from NASA’s Wide-field Infrared Survey Explorer mission and other surveys. We applied this new catalog of well-vetted disk candidates to search for new members of nearby young stellar associations (YSAs) using a novel technique based on Gaia data and virtual reality (VR). We examined AB Doradus, Argus, β Pictoris, Carina, Columba, Octans-Near, Tucana–Horologium, and TW Hya by displaying them in VR together with other nearby stars, color coded to show infrared excesses found via Disk Detective. Using this method allows us to find new association members in mass regimes where isochrones are degenerate. We propose 10 new YSA members with infrared excesses: three of AB Doradus (HD 44775, HD 40540 and HD 44510), one of β Pictoris (HD 198472), two of Octans-Near (HD 157165 and BD+35 2953), and four disk-hosting members of a combined population of Carina, Columba, and Tucana–Horologium: CPD-57 937, HD 274311, HD 41992, and WISEA J092521.90-673224.8. This last object (J0925) appears to be an extreme debris disk with a fractional infrared luminosity of 3.7 × 10⁻². We also propose two new members of AB Doradus that do not show infrared excesses: TYC 6518-1857-1 and CPD-25 1292. We find HD 15115 appears to be a member of Tucana–Horologium rather than β Pictoris. We advocate for membership in Columba–Carina of HD 30447, CPD-35 525, and HD 35841. Finally, we propose that three M dwarfs, previously considered members of Tucana–Horologium are better considered a separate association, tentatively called “Smethells 165”.

Recent work has revealed that the light curves of hydrogen-poor (Type I) superluminous supernovae (SLSNe), thought to be powered by magnetar central engines, do not always follow the smooth decline predicted by a simple magnetar spin-down model. Here we present the first systematic study of the prevalence and properties of “bumps” in the post-peak light curves of 34 SLSNe. We find that the majority (44%–76%) of events cannot be explained by a smooth magnetar model alone. We do not find any difference in supernova properties between events with and without bumps. By fitting a simple Gaussian model to the light-curve residuals, we characterize each bump with an amplitude, temperature, phase, and duration. We find that most bumps correspond with an increase in the photospheric temperature of the ejecta, although we do not see drastic changes in spectroscopic features during the bump. We also find a moderate correlation (ρ ≈ 0.5; p ≈ 0.01) between the phase of the bumps and the rise time, implying that such bumps tend to happen at a certain “evolutionary phase,” (3.7 ± 1.4)t_rise. Most bumps are consistent with having diffused from a central source of variable luminosity, although sources further out in the ejecta are not excluded. With this evidence, we explore whether the cause of these bumps is intrinsic to the supernova (e.g., a variable central engine) or extrinsic (e.g., circumstellar interaction). Both cases are plausible, requiring low-level variability in the magnetar input luminosity, small decreases in the ejecta opacity, or a thin circumstellar shell or disk.

We have developed a tracking algorithm to determine the speeds of supra-arcade downflows (SADs) and set up a system to automatically track SADs and measure some interesting parameters. By conducting an analysis of six flares observed by the Atmospheric Imaging Assembly on the Solar Dynamics Observatory, we detect more smaller and slower SADs than prior work, due to the higher spatial resolution of our observational data. The inclusion of these events with smaller and slower SADs directly results in lower median velocities and widths than in prior work, but the fitted distributions and evolutions of the parameters still show good consistency with prior work. The observed distributions of the widths, speeds, and lifetimes of SADs are consistent with log-normal distributions, indicating that random and unstable processes are responsible for generating SADs during solar eruptions. Also, we find that the fastest SADs occur at approximately the middle of the height ranges. The number of SADs in each image versus time shows that there are “rest phases” of SADs, when few SADs are seen. These findings support the idea that SADs originate from a fluid instability. We compare our results with a numerical simulation that generates SADs using a mixture of the Rayleigh–Taylor instability and the Richtmyer–Meshkov instability, and find that the simulation generates quantities that are consistent with our observational results.

We model long-term variations in the scintillation of binary pulsar PSR J1603−7202, observed by the 64 m Parkes radio telescope (Murriyang) between 2004 and 2016. We find that the time variation in the scintillation arc curvature is well-modeled by scattering from an anisotropic thin screen of plasma between the Earth and the pulsar. Using our scintillation model, we measure the inclination angle and longitude of ascending node of the orbit, yielding a significant improvement over the constraints from pulsar timing. From our measurement of the inclination angle, we place a lower bound on the mass of J1603−7202's companion of ≳0.5 M_⊙ assuming a pulsar mass of ≳1.2 M_⊙. We find that the scintillation arcs are most pronounced when the electron column density along the line of sight is increased, and that arcs are present during a known extreme scattering event. We measure the distance to the interstellar plasma and its velocity, and we discuss some structures seen in individual scintillation arcs within the context of our model.

This paper compares the population of binary black hole (BBH) mergers detected by LIGO/Virgo with selected long gamma-ray burst (GRB) world models convolved with a delay function (LGRBs are used as a tracer of stellar-mass BH formation). The comparison involves the redshift distribution and the fraction of LGRBs required to produce the local rate of BBH mergers. We find that BBH mergers and LGRBs cannot have the same formation history, unless BBH mergers have a long coalescence time of several Gyr. This would imply that BHs born during the peak of long GRB formation at redshift z ≈ 2−3 merge within the horizon of current GW interferometers. We also show that LGRBs are more numerous than BBH mergers, meaning that most of them do not end their lives in BBH mergers. We interpret these results as an indication that BBH mergers and LGRBs constitute two distinct populations of stellar-mass BHs, with LGRBs being more frequent than BBH mergers. We speculate that the descendants of LGRBs may resemble galactic high-mass X-ray binaries more than BBH mergers. Finally, we discuss the possible existence of a subpopulation of fast-spinning LGRB descendants among BBH mergers, showing that this population, if it exists, is expected to become dominant beyond redshift z ≈ 1, leading to a change in the observed properties of BBH mergers.

The typical spectrum of the prompt emission of gamma-ray bursts (GRBs) indicates that the electron cooling is suppressed in spite of the strong magnetic field in the standard synchrotron model. Recent particle-in-cell simulations show that the particle acceleration by magnetic reconnection in a magnetically dominated plasma can lead to small pitch angles especially in a low-energy region. Such a small pitch angle prevents electrons from cooling via synchrotron radiation. In this paper, taking into account the effects of the synchrotron cooling and the adiabatic cooling, we numerically calculate the synchrotron spectra with anisotropic electron distributions. If we require a Poynting flux larger than 10⁵⁰ erg s⁻¹ as the model is motivated by magnetic reconnection, the bulk Lorentz factor of ∼1000 and the electron minimum Lorentz factor of γ_min ∼ 10⁴ are required to reproduce the typical GRB spectrum.

Weak gravitational lensing is a powerful statistical tool for probing the growth of cosmic structure and measuring cosmological parameters. However, as shown by studies such as by Ménard et al., dust in the circumgalactic region of halos dims and reddens background sources. In a weak lensing analysis, this selects against sources behind overdense regions; since there is more structure in overdense regions, we will underestimate the amplitude of density perturbations σ₈ if we do not correct for the effects of circumgalactic dust. To model the dust distribution we employ the halo model. Assuming a fiducial dust mass profile based on measurements from Ménard et al., we compute the ratio Z of the systematic error to the statistical error for a survey similar to the Nancy Grace Roman Space Telescope reference survey (2000 deg² area, single-filter effective source density 30 galaxies arcmin⁻²). For a wave band centered at 1580 nm (H band), we find that Z_H = 0.37. For a similar survey with wave band centered at 620 nm (r band), we also computed Z_r = 2.8. Within our fiducial dust model, since Z_r > 1, the systematic effect of dust will be significant on weak lensing image surveys. We also computed the dust bias on the amplitude of the power spectrum, σ₈, and found it to be for each wave band Δσ₈/σ₈ = −3.1 × 10⁻⁴ (H band) or −2.2 × 10⁻³ (r band) if all other parameters are held fixed (the forecast Roman statistical-only error σ(σ₈)/σ₈ is 9 × 10⁻⁴).

Massive dense clumps in the Large Magellanic Cloud can be an important laboratory to explore the formation of populous clusters. We report multiscale ALMA observations of the N159W-North clump, which is the most CO-intense region in the galaxy. High-resolution CO isotope and 1.3 mm continuum observations with an angular resolution of ∼025 (∼0.07 pc) revealed more than five protostellar sources with CO outflows within the main ridge clump. One of the thermal continuum sources, MMS-2, shows an especially massive/dense nature whose total H₂ mass and peak column density are ∼10⁴M_⊙ and ∼10²⁴ cm⁻², respectively, and harbors massive (∼100 M_⊙) starless core candidates identified as its internal substructures. The main ridge containing this source can be categorized as one of the most massive protocluster systems in the Local Group. The CO high-resolution observations found several distinct filamentary clouds extending southward from the star-forming spots. The CO (1–0) data set with a larger field of view reveals a conical, ∼30 pc long complex extending toward the northern direction. These features indicate that a large-scale gas compression event may have produced the massive star-forming complex. Based on the striking similarity between the N159W-North complex and the other two previously reported high-mass star-forming clouds in the nearby regions, we propose a “teardrops inflow model” that explains the synchronized, extreme star formation across >50 pc, including one of the most massive protocluster clumps in the Local Group.

Coronal plumes are long, ray-like, open structures that have been considered as possible sources of the solar wind. Their origin in the largely unipolar coronal holes has long been a mystery. Earlier spectroscopic and imaging observations revealed blueshifted plasma and propagating disturbances (PDs) in plumes that are widely interpreted in terms of flows and/or propagating slow-mode waves, but these interpretations (flows versus waves) remain under debate. Recently we discovered an important clue about plume internal structure: dynamic filamentary features called plumelets, which account for most of the plume emission. Here we present high-resolution observations from the Solar Dynamics Observatory/Atmospheric Imaging Assembly and the Interface Region Imaging Spectrograph that revealed numerous, quasi-periodic, tiny jets (so-called jetlets) associated with transient brightening, flows, and plasma heating at the chromospheric footpoints of the plumelets. By analogy to larger coronal jets, these jetlets are most likely produced within the plume base by magnetic reconnection between closed and open flux at stressed 3D null points. The jetlet-associated brightenings are in phase with plumelet-associated PDs, and vary with a period of ∼3–5 minutes, which is remarkably consistent with the photospheric/chromospheric p-mode oscillation. This reconnection at the open-closed boundary in the chromosphere/transition region is likely modulated or driven by local manifestations of the global p-mode waves. The jetlets extend upward to become plumelets, contribute mass to the solar wind, and may be sources of the switchbacks recently detected by the Parker Solar Probe.

We explore the electromagnetic counterparts that will associate with binary-neutron-star mergers for the case that remnant massive neutron stars survive for ≳0.5 s after the merger. For this study, we employ the outflow profiles obtained by long-term general-relativistic neutrino-radiation magnetohydrodynamics simulations with a mean-field dynamo effect. We show that a synchrotron afterglow with high luminosity can be associated with the merger event if the magnetic fields of the remnant neutron stars are significantly amplified by the dynamo effect. We also perform a radiative transfer calculation for kilonovae and find that, for the highly amplified magnetic field cases, the kilonovae can be bright in the early epoch (t ≤ 0.5 d), while it shows the optical emission which rapidly declines in a few days and the very bright near-infrared emission which lasts for ∼10 days. All these features have not been found in GW170817, indicating that the merger remnant neutron star formed in GW170817 might have collapsed to a black hole within several hundreds milliseconds or magnetic-field amplification might be a minor effect.

For revealing the first step of planet formation, it is important to understand how and when dust grains become larger in a disk around a protostar. To investigate the grain growth, we analyze dust continuum emission toward a disk around the Class I protostar L1489 IRS at 0.9 and 1.3 mm wavelengths obtained by the Atacama Large Millimeter/submillimeter Array. The dust continuum emission extends to a disk radius (r) of r ∼ 300 au, and the spectral index (α) is derived to be α ∼ 3.6 at a radius of r ∼ 100–300 au, similar to the interstellar dust. Therefore, the grain growth does not occur significantly in the outer disk (r ∼ 100–300 au). Furthermore, we tentatively identify a ring-like substructure at r ∼ 90 au even though the spatial resolution and sensitivity are not enough to determine this structure. If this is the real ring structure, the ring position and small dust in the disk outer part are consistent with the idea of the growth front. These results suggest that the L1489 protostellar disk may be the beginning of planet formation.

The Fourier transformation is an effective and efficient operation of Gaussianization at the one-point level. Using a set of N-body simulation data, we verified that the one-point distribution functions of the dark matter momentum divergence and density fields closely follow complex Gaussian distributions. The one-point distribution function of the quotient of two complex Gaussian variables is introduced and studied. Statistical theories are then applied to model one-point statistics about the growth of individual Fourier modes of the dark matter density field, which can be obtained by the ratio of two Fourier-transformed cosmic fields. Our simulation results proved that the models based on the Gaussian approximation are impressively accurate, and our analysis revealed many interesting aspects of the growth of dark matter’s density fluctuation in Fourier space.

We present an updated prescription for the equilibrium tides suitable for population synthesis codes. A grid of 1D evolutionary models was created and the viscous timescale was calculated for each detailed model. A metallicity-dependent power-law relation was fitted to both the convective cores and convective envelopes of the models. The prescription was implemented into the population synthesis code Binary Star Evolution and predicts a 16.5% reduction in the overall number of merges, with those involving main-sequence stars most affected. The new prescription also reduces the overall supernova rate by 3.6% with individual channels being differently affected. The single degenerate Ia supernova occurrence is reduced by 12.8%. The merging of two carbon oxygen white dwarfs to cause a Ia supernova occurs 16% less frequently. The number of subsynchronously rotating stars in close binaries is substantially increased with our prescription, as is the number of noncircularized systems at the start of common-envelope evolution.

Long-term solar activity can be studied using several parameters. Some of the most used are based on the sunspot counting. The active day fraction (ADF) is the simplest index derived from this counting. It is reliable in periods of low solar activity such as the Maunder minimum (MM). In this work, we study the relationship between the ADF and the sunspot number. We have obtained that the optimal fit of that relationship is an exponential function whose exponent is a degree 3 polynomial including all data except those with ADF equal to 100%. Then, we use that fit to estimate the sunspot number during the MM from the ADF calculated from the most recent sunspot group number database. Our estimations of the annual sunspot numbers are below 15, except that for 1656, which is 40.8, whereas our estimations of the triennial sunspot numbers are below 10 from 1648 to 1714. We have found peaks of the solar cycle in the middle of the 1650s, 1670s, 1680s, and 1700s but no clear evidence of solar cycle in the 1660s and 1690s, likely due to the scarcity of the available data. Our results agree with previous works obtaining values significantly higher than those of the group sunspot number derived by Hoyt and Schatten in 1998 but still fully compatible with a grand minimum period.

We present the results of high-resolution spectropolarimetric observations of the optically dominant component in the rare hydrogen-deficient binary system υ Sgr. Only a small number of such systems in a very late phase of helium shell burning are currently known. The mass transfer from the donor star in binary systems usually leads to the stripping of its hydrogen envelope. Consequently, since the mass of the secondary increases, it appears rejuvenated. Using a few ESO FORS 1 low-resolution spectropolarimetric observations of this system, Hubrig et al. announced in 2009 the presence of a magnetic field of the order of −70 to −80 G. Here we report on more recent high-resolution ESO HARPS spectropolarimetric observations showing that the primary in υ Sgr is a spectrum variable star and possesses a weak magnetic field of the order of a few tens of Gauss. The detection of a magnetic field in this rare hydrogen-deficient binary is of particular interest, as such systems are frequently discussed as probable progenitors of core-collapse supernovae and gravitational-wave sources. Future magnetic studies of such systems would be worthwhile to gain deeper insights into the role of magnetic fields in the evolution of massive stars in binary systems.

Gaia used a large sample of photometrically selected active galactic nuclei (AGNs) and quasars to remove the residual spin of its global proper motion system in order to achieve a maximally inertial reference frame. A small fraction of these reference objects have statistically significant astrometric proper motions in Gaia EDR3. We compile a source sample of 105,593 high-fidelity AGNs with accurate spectroscopically determined redshifts above 0.5 from the SDSS and normalized proper motions below 4. The rate of genuinely perturbed proper motions is at least 0.17%. A smaller high completeness sample of 152 quasars with excess proper motions at a confidence level of 0.9995 is examined in detail. Pan-STARRS images and Gaia-resolved pairs reveal that 29% of the sample are either double sources or gravitationally lensed quasars. An Anderson–Darling test on parameters of a smaller high-reliability sample and their statistical controls reveals 17 significant factors that favor multiplicity and multi-source structure as the main cause of perturbed astrometry. Using a nearest-neighbor distance statistical analysis and counts of close companions in Gaia on a much larger initial sample of AGNs, an excess of closely separated sources in Gaia is detected. At least 0.33% of all optical quasars are genuinely double or multiply imaged. We provide a list of 44 candidate double or multiple AGNs and four previously known gravitational lenses. Many proper motion quasars may be more closely separated, unresolved doubles exhibiting the variability imposed motion effect, and a smaller fraction may be chance alignments with foreground stars causing weak gravitational lensing.

We present a series of numerical solutions of spherically symmetric stationary flows with nuclear burning accreted by a neutron star (or black hole). We consider the accretion of matter composed of carbon and oxygen, which mimics the flow after a neutron star is engulfed by a CO star or the CO core of a massive star. It is found that there are two types of transonic solutions depending on the accretion rate. The flow with a low accretion rate reaches the center (or the surface of the central object) at supersonic speeds. The other type with a high accretion rate has another sonic point inside the transonic point and the flow truncates at the sonic point. The critical accretion rate dividing these two types is derived as a function of the mass of the central object and the specific enthalpy in the ambient matter. We discuss implications from the solutions for a new mechanism of super-Chandrasekhar Type Ia supernovae and Type Icn supernovae.

One of the challenges in understanding the quenching processes for galaxies is connecting progenitor star-forming populations to their descendant quiescent populations over cosmic time. Here we attempt a novel approach to this challenge by assuming that the underlying stellar mass distribution of galaxies is not significantly altered during environmental-quenching processes that solely affect the gas content of cluster galaxies, such as strangulation and ram pressure stripping. Using the deep, high-resolution photometry of the Hubble Frontier Fields, we create resolved stellar mass maps for both cluster and field galaxies, from which we determine 2D Sérsic profiles, and obtain Sérsic indices and half-mass radii. We classify the quiescent cluster galaxies into disk-like and bulge-like populations based on their Sérsic indices, and find that bulge-like quiescent galaxies dominate the quiescent population at higher masses (M_⋆ > 10^9.5M_⊙), whereas disk-like quiescent galaxies dominate at lower masses (10^8.5M_⊙ < M_⋆ < 10^9.5M_⊙). Using both the Sérsic indices and half-mass radii, we identify a population of quiescent galaxies in clusters that are morphological analogs of field star-forming galaxies. These analogs are interpreted to be star-forming galaxies that had been environmentally quenched. We use these morphological analogs to compute the environmental-quenching efficiency, and we find that the efficiency decreases with increasing stellar mass. This demonstrates that environmental quenching is more effective on less massive galaxies and that the effect of environment on quenching galaxies is not completely separable from the effect of mass on quenching galaxies.

We present a tabulated version of our slim-disk model for fitting tidal disruption events (TDEs). We create a synthetic X-ray spectral library by ray-tracing stationary general relativistic slim disks and including gravitational redshift, Doppler, and lensing effects self-consistently. We introduce the library to reduce computational expense and increase access for fitting future events. Fitting requires interpolation between the library spectra; the interpolation error in the synthetic flux is generally <10% (it can rise to 40% when the disk is nearly edge-on). We fit the X-ray spectra of the TDEs ASASSN-14li and ASASSN-15oi, successfully reproducing our earlier constraints on black hole mass M_• and spin a_• from full on-the-fly ray-tracing. We use the library to fit mock observational data to explore the degeneracies among parameters, finding that (1) spectra from a hotter thermal disk and edge-on inclination angle offer tighter constraints on M_• and a_•; (2) the constraining power of spectra on M_• and a_• increases as a power law with the number of X-ray counts, and the index of the power law is higher for hotter thermal disk spectra; (3) multiepoch X-ray spectra partially break the degeneracy between M_• and a_•; (4) the time-dependent level of X-ray absorption can be constrained from spectral fitting. The tabulated model and slim-disk model are available at https://doi.org/10.25739/hfhz-xn60.

Interactions between plasma particles and electromagnetic waves play a crucial role in the dynamics and regulation of the state of space environments. From plasma physics theory, the characteristics of the waves and their interactions with the plasma strongly depend on the composition of the plasma, among other factors. In the case of the Earth’s magnetosphere, the plasma is usually composed of electrons, protons, O+ ions, and He+ ions, all with their particular properties and characteristics. Here, using plasma parameters relevant for the inner magnetosphere, we study the dispersion properties of kinetic Alfvén waves (KAWs) in a plasma composed of electrons, protons, He+ ions, and O+ ions. We show that heavy ions induce significant changes to the dispersion properties of KAWs, such as polarization, compressibility, and the electric-to-magnetic amplitude ratio, and therefore the propagation of KAWs is highly determined by the relative abundance of He+ and O+ in the plasma. These results, when discussed in the context of observations in the Earth’s magnetosphere, suggest that for many types of studies based on theory and numerical simulations, the inclusion of heavy ions should be customary for the realistic modeling of plasma phenomena in the inner magnetosphere or other space environments in which heavy ions can contribute a substantial portion of the plasma, such as planetary magnetospheres and comet plasma tails.

The Taylor microscale is a fundamental length scale in turbulent fluids, representing the end of fluid properties and onset of dissipative processes. The Taylor microscale can also be used to evaluate the Reynolds number in classical turbulence theory. Although the solar wind is weakly collisional, it approximately behaves as a magnetohydrodynamic (MHD) fluid at scales larger than the kinetic scale. As a result, classical fluid turbulence theory and formalisms are often used to study turbulence in the MHD range. Therefore, a Taylor microscale can be used to estimate an effective Reynolds number in the solar wind. NASA’s Parker Solar Probe (PSP) has reached progressively closer to the Sun than any other spacecraft before. The collected data have revealed many new findings in the near-Sun solar wind. Here, we use the PSP data to estimate the Taylor microscale and effective Reynolds number near the Sun. We find that the Taylor microscale and Reynolds number are small compared to the corresponding near-Earth values, indicating a solar wind that has been less processed by turbulence, with very small-scale dissipative processes near the Sun.

We make the first observation-based calculation of the energy that goes into cosmic ray protons versus cosmic ray electrons in shock acceleration during structure formation. We find a ratio of energy in cosmic ray protons to energy in cosmic ray electrons of 0.86. This value, calculated from the nonthermal X-ray component reported here from RTXE and the Fermi LAT upper limit for gamma-ray emission, is significantly lower than theoretical estimates that place most of the nonthermal energy in protons. Our estimate is based on the detection of nonthermal X-ray emission using the 3–20 keV RXTE spectrum, which shows residual emission not well modeled by a single thermal component. The statistical significance of adding a nonthermal, power-law component is 96%. The significance of adding a second thermal component is 90%. The addition of a component consisting of full cosmic X-ray background fluctuation to an isothermal model is significant with 92% confidence. The cumulative probability for the two-thermal-component model is 81% and 90% for the thermal plus power law. Thus the model with nonthermal emission is the preferred description of the data. Evidence of shock heating between the clusters in the spectro-imaging data of XMM, Chandra, and Suzaku indicates that a cosmic ray component should also be present and supports a nonthermal interpretation for the additional component. The bolometric nonthermal X-ray luminosity is 1.6 × 10⁴⁴ ergs s⁻¹, 36% of the total X-ray emission in the 0.1–100 keV band.

The observed large variation in the abundance of deuterium (D) in the interstellar medium suggests that a significant fraction of D may be depleted into polycyclic aromatic hydrocarbons (PAHs). Signatures of the deuteration of PAHs are expected to appear most clearly through the C–D stretching modes at 4.4–4.7 μm, whose strengths in emission spectra relative to those of the C–H stretching modes at 3.3–3.5 μm provide the relative abundance of D to hydrogen (H) in PAHs, once we have accurate relative band strengths of both stretching modes. We report experimental results of the band strengths of the C–D stretching modes relative to the C–H stretching modes. We employ a laboratory analog of interstellar carbonaceous dust, Quenched Carbonaceous Composite (QCC), and synthesize deuterated QCC (D-QCC) by replacing the QCC starting gas of CH₄ with mixtures of CH₄ and CD₄ with various ratios. Infrared spectra of D-QCC are taken to estimate the relative band strengths of the stretching modes, while the D/H ratios in the D-QCC samples are measured with a nanoscale secondary ion mass spectrometer. We obtain relative strengths of aromatic and aliphatic C–D to C–H stretches as 0.56 ± 0.04 and 0.38 ± 0.01 per D/H, respectively. The ratio for the aromatic stretches is in good agreement with the results of theoretical calculations, while that for the aliphatic stretches is smaller than that for the aromatic stretches. The present results do not significantly change the D/H ratios in interstellar PAHs that have previously been estimated from observed spectra.

We report the result of our independent image reconstruction of the M87 from the public data of the Event Horizon Telescope Collaborators (EHTC). Our result is different from the image published by the EHTC. Our analysis shows that (a) the structure at 230 GHz is consistent with those of lower-frequency very long baseline interferometry observations, (b) the jet structure is evident at 230 GHz extending from the core to a few milliarcsecond, although the intensity rapidly decreases along the axis, and (c) the “unresolved core” is resolved into three bright features presumably showing an initial jet with a wide opening angle of ∼70°. The ring-like structures of the EHTC can be created not only from the public data but also from the simulated data of a point image. Also, the rings are very sensitive to the field-of-view (FOV) size. The u−v coverage of the Event Horizon Telescope (EHT) lacks ∼ 40 μas fringe spacings. Combining with a very narrow FOV, it created the ∼40 μas ring structure. We conclude that the absence of the jet and the presence of the ring in the EHTC result are both artifacts owing to the narrow FOV setting and the u−v data sampling bias effect of the EHT array. Because the EHTC's simulations only take into account the reproduction of the input image models, and not those of the input noise models, their optimal parameters can enhance the effects of sampling bias and produce artifacts such as the ∼40 μas ring structure, rather than reproducing the correct image.

We searched the northern hemisphere fields of the Galaxy Evolution Explorer Time Domain Survey for galaxies with UV variability indicative of active galactic nuclei (AGNs). We identified 48 high-probability candidate AGNs from a parent sample of 1819 galaxies in the NASA Sloan Atlas catalog. We further characterized these systems using optical spectroscopic diagnostics, Wide-field Infrared Survey Explorer IR color selection criteria, and spectral energy distribution modeling. Of the 48 candidates, eight were identified as AGNs from optical emission lines, two were identified by their IR colors, and 28 were identified through spectral energy decomposition. Observational biases of each selection method are discussed in connecting these AGN subsamples to another. By selecting AGNs based on UV variability, we also identified six low-mass AGN candidates, all of which would have been missed by spectroscopic selection.

Recent theoretical and numerical studies of Type Ia supernovae (SNe Ia) explosions within the single-degenerate scenario suggest that the nondegenerate companions could survive during the supernova impact and could be detectable in nearby supernova remnants. However, observational efforts show less promising evidence of the existence of surviving companions from the standard single-degenerate channels. The spin-up/spin-down models are possible mechanisms to explain the nondetection of surviving companions. In these models, the spin-up phase could increase the critical mass for explosion, leading to a super-Chandrasekhar-mass explosion, and the spin-down phase could lead to extra mass loss and angular momentum redistribution. Since the spin-down timescale for the delayed explosion of a rotating white dwarf is unclear, in this paper we explore a vast parameter space of main-sequence-like surviving companions via two-dimensional hydrodynamic simulations of supernova impact and the subsequent stellar evolution of surviving companions. Tight universal relations to describe the mass-stripping effect, supernova kick, and depth of supernova heating are provided. Our results suggest that the not-yet-detected surviving companions from observations of nearby SN Ia remnants might favor low-mass companions, short binary separation, or stronger supernova explosion energies than the standard single-degenerate channels.

We use 789 disk-like, star-forming galaxies (with 596 H i detections) from H i follow-up observations for the SDSS-IV MaNGA survey to study the possible role of inner H i gas in causing secondary dependences in the mass–gas-phase metallicity relation. We use the gas-phase metallicity derived at the effective radii of the galaxies. We derive the inner H i mass within the optical radius, but also use the total H i mass and star formation rate (SFR) for a comparison. We confirm the anticorrelation between the total H i mass and gas-phase metallicity at fixed stellar mass, but the anticorrelation is significantly strengthened when the total H i mass is replaced by the inner H i mass. Introducing a secondary relation with the inner H i mass can produce a small but noticeable decrease (16%) in the scatter of the mass–gas-phase metallicity relation, in contrast to the negligible effect with the SFR. The correlation with the inner H i mass is robust when using different diagnostics of metallicity, but the correlation with SFR is not. The correlation with the inner H i mass becomes much weaker when the gas-phase metallicity is derived in the central region instead of at the effective radius. These results support the idea that the scatter in the mass–metallicity relation is regulated by gas accretion, and not directly by the SFR, and stress the importance of deriving the gas mass and the metallicity from roughly the same region. The new relation between inner H i mass and gas-phase metallicity will provide new constraints for chemical and galaxy evolution models.

Recently, a collision-induced magnetic reconnection (CMR) mechanism was proposed to explain a dense filament formation in the Orion A giant molecular cloud. A natural question is whether CMR works elsewhere in the Galaxy. As an initial attempt to answer the question, this paper investigates the triggering of CMR and the production of dense gas in a flat-rotating disk with a modified Bisymmetric spiral (BSS) magnetic field. Cloud−cloud collisions at field reversals in the disk are modeled with the Athena++ code. Under the condition that is representative of the warm neutral medium, the cloud−cloud collision successfully triggers CMR at different disk radii. However, dense gas formation is hindered by the dominating thermal pressure, unless a moderately stronger initial field ≳5 μG is present. The strong-field model, having a larger Lundquist number S_L and lower plasma β, activates the plasmoid instability in the collision midplane, which is otherwise suppressed by the disk rotation. We speculate that CMR can be common if more clouds collide along field reversals. However, to witness the CMR process in numerical simulations, we need to significantly resolve the collision midplane with a spatial dynamic range ≳10⁶. If Milky Way spiral arms indeed coincide with field reversals in BSS, it is possible that CMR creates or maintains dense gas in the arms. High-resolution, high-sensitivity Zeeman/Faraday rotation observations are crucial for finding CMR candidates that have helical fields.

Quiescent mass loss during the red supergiant (RSG) phase has been shown to be far lower than prescriptions typically employed in single-star evolutionary models. Importantly, RSG winds are too weak to drive the production of Wolf-Rayet (WR) stars and stripped-envelope supernovae (SE-SNe) at initial masses of roughly 20–40 M_⊙. If single stars are to make WR stars and SE-SNe, this shifts the burden of mass loss to rare dust-enshrouded RSGs (DE-RSGs), objects claimed to represent a short-lived, high-mass-loss phase. Here, we take a fresh look at the purported DE-RSGs. By modeling the mid-IR excesses of the full sample of RSGs in the Large Magellanic Cloud, we find that only one RSG has both a high mass-loss rate ( ≥ 10⁻⁴M_⊙ yr⁻¹) and a high optical circumstellar dust extinction (7.92 mag). This RSG is WOH G64, and it is the only one of the 14 originally proposed DE-RSGs that is actually dust enshrouded. The rest appear to be either normal RSGs without strong IR excess, or lower-mass asymptotic giant branch stars. Only one additional object in the full catalog of RSGs (not previously identified as a DE-RSG) shows strong mid-IR excess. We conclude that if DE-RSGs do represent a pre-SN phase of enhanced in single stars, it is extremely short-lived, only capable of removing ≤2 M_⊙ of material. This rules out the single-star post-RSG pathway for the production of WR stars, luminous blue variables, and SE-SNe. Single-star models should not employ -prescriptions based on these extreme objects for any significant fraction of the RSG phase.

We report the results from our study of the blazar S5 1803+784 carried out using quasi-simultaneous B, V, R, and I observations from 2020 May to 2021 July on 122 nights. Our observing campaign detected a historically bright optical flare during MJD 59,063.5−MJD 59,120.5. We also found the source in its brightest (R_mag = 13.617) and faintest (R_mag = 15.888) states to date. On 13 nights, covering both flaring and nonflaring periods, we searched for intraday variability using the power-enhanced F-test and the nested ANOVA test. We found significant variability in 2 of these 13 nights. However, no such variability was detected during the flaring period. From correlation analysis, we observed that the emission in all optical bands were strongly correlated with a time lag of ∼0 days. To get insights into its dominant emission mechanisms, we generated the optical spectral energy distributions of the source on 79 nights and estimated the spectral indices by fitting a simple power law. The spectral index varied from 1.392 to 1.911 and showed significant variations with time and R-band magnitude. We detected a mild bluer-when-brighter (BWB) trend during the whole monitoring period and a much stronger BWB trend during the flare. We also carried out a periodicity search using four different methods and found no significant periodicity during our observation period. Based on the analysis during the flaring state of the source one can say that the emissions most likely originate from the jet rather than from the accretion disk.

Magnetic switchbacks, or sudden reversals in the magnetic field’s radial direction, are one of the more striking observations of the Parker Solar Probe (PSP) in its mission thus far. While their precise production mechanisms are still unknown, the two main theories are via interchange reconnection events and in situ generation. In this work, density and abundance variations of alpha particles are studied inside and outside individual switchbacks. We find no consistent compositional differences in the alpha particle abundance ratio, n_αp, inside versus outside switchbacks, nor do we observe any signature when separating the switchbacks according to V_αp/V_pw, the ratio of the alpha–proton differential speed to the wave phase speed (the speed at which the switchback is traveling). We argue that these measurements cannot be used to rule in favor of one production mechanism over the other, due to the distance between PSP and the postulated interchange reconnection events. In addition, we examine the 3D velocity fluctuations of protons and alpha particles within individual switchbacks. While switchbacks are always associated with increases in proton velocity, alpha velocities may be enhanced, unchanged, or decrease. This is due to the interplay between V_pw and V_αp, with the Alfvénic motion of the alpha particles vanishing as the difference ∣V_pw – V_αp∣ decreases. We show how the Alfvénic motion of both the alphas and the protons through switchbacks can be understood as an approximately rigid arm rotation about the location of the wave frame, and illustrate that the wave frame can therefore be estimated using particle measurements alone, via sphere fitting.

We show the results of a study using the spectral synthesis technique study for the full MaNGA sample showing their chemical enrichment history (ChEH) as well as the evolution of the stellar mass–metallicity relation (MZR) over cosmic time. We find that the more massive galaxies became enriched first and the lower-mass galaxies did so later, producing a change in the MZR that becomes shallower in time. Separating the sample into morphology and star-forming status bins, some particularly interesting results appear: The mass dependence of the MZR becomes less relevant for later morphological types, to the extent that it inverts for Sd/Irr galaxies, suggesting that morphology is at least as important a factor as mass in the chemical evolution. The MZR for the full sample shows a flattening at the high-mass end and another in the low-mass range, but the former only appears for retired galaxies, while the latter only appears for star-forming galaxies. We also find that the average metallicity gradient is currently negative for all mass bins, but for low-mass galaxies, it was inverted at some point in the past, before which all galaxies had a positive gradient. We also compare how diverse the ChEHs are in the different bins we considered, as well as what primarily drives the diversity: By how much galaxies become enriched, or how quickly they do so.

Based on the observations from the Super Dual Auroral Radar Network at the Zhongshan Station (−74.9 MLAT, 97.2 MLON) and GOES satellites X-ray sensor, we present the first statistical study of the dayside ionospheric short-wave fadeout (SWF) events on the Southern Hemispheric high latitude from the years 2010–2019 and provide a normal characteristic of SWF with onset of 6 minutes 54 s, blackout of 20 minutes 24 s, and recovery of 39 minutes 36 s, respectively. All the SWF events in this work are selected to be caused by extreme flares. The statistical analysis shows both short-type and long-type SWF onset phases. Onset/blackout phase duration of long events is highly correlated with flare duration (0.79, 0.60), the SWF is mainly driven by the flare radiation profile, and the soft X-ray flux rise rate is higher for short-onset events than for most long-onset events, which is the main reason for the difference between the two types of events. In addition, the effect of ionospheric sluggishness on long-onset events also needs to be considered. The relationship between each phase’s durations of long SWFs and the effective peak X-ray flux is not obvious. However, the correlation between the integrated effective X-ray flux and the onset/blackout phase duration of long events is significant.

By adopting the intermediate and power-law scale factors, we study the tachyon inflation with constant sound speed. We perform some numerical analysis on the perturbation and non-Gaussianity parameters in this model and compare the results with observational data. By using the constraints on the scalar spectral index and tensor-to-scalar ratio obtained from Planck2018 TT, TE, and EE+lowE+lensing+BAO+BK14 data; the constraints on the running of the scalar spectral index obtained from Planck2018 TT, TE, and EE+lowEB+lensing data; and the constraints on tensor spectral index obtained from Planck2018 TT, TE, and EE+lowE+lensing+BK14+BAO+LIGO and Virgo2016 data, we find the observationally viable ranges of the model’s parameters at both 68% CL and 95% CL. We also analyze the non-Gaussian features of the model in the equilateral and orthogonal configurations. Based on Planck2018 TTT, EEE, TTE, and EET data, we find constraints on the sound speed of 0.276 ≤ c_s ≤ 1 at 68% CL, 0.213 ≤ c_s ≤ 1 at 95% CL, and 0.186 ≤ c_s ≤ 1 at 97% CL.

We present the final sample of the Exploration of Local VolumE Satellites (ELVES) survey, a survey of the dwarf satellites of a nearly volume-limited sample of Milky Way (MW)−like hosts in the Local Volume. Hosts are selected simply via a cut in luminosity ( mag) and distance (D < 12 Mpc). We cataloged the satellites of 25 of the 31 such hosts, with another five taken from the literature. All hosts are surveyed out to at least 150 projected kpc ( ∼ R_vir/2), with the majority surveyed to 300 kpc ( ∼ R_vir). Satellites are detected using a consistent semiautomated algorithm specialized for low surface brightness dwarfs. As shown through extensive tests with injected galaxies, the catalogs are complete to M_V ∼ −9 mag and μ_0,V ∼ 26.5 mag arcsec⁻². Candidates are confirmed to be real satellites through distance measurements including redshift, tip of the red giant branch, and surface brightness fluctuations. Across all 30 surveyed hosts, there are 338 confirmed satellites with M_V < −9 mag, with a further 106 candidates awaiting distance measurement. For the vast majority of these, we provide consistent multiband Sérsic photometry. We show that satellite abundance correlates with host mass, with the MW being quite typical among comparable systems, and that satellite quenched fraction rises steeply with decreasing satellite mass, mirroring the quenched fraction for the MW and M31. The ELVES survey represents a massive increase in the statistics of surveyed systems with known completeness, and the provided catalogs are a unique data set to explore various aspects of small-scale structure and dwarf galaxy evolution.

Halos of similar mass and redshift exhibit a large degree of variability in their differential properties, such as dark matter, hot gas, and stellar mass density profiles. This variability is an indicator of diversity in the formation history of these dark matter halos that is reflected in the coupling of scatters about the mean relations. In this work, we show that the strength of this coupling depends on the scale at which halo profiles are measured. By analyzing the outputs of the IllustrisTNG hydrodynamical cosmological simulations, we report the radial- and mass-dependent couplings between the dark matter, hot gas, and stellar mass radial density profiles utilizing the population diversity in dark matter halos. We find that for the same mass halos, the scatters in the density of baryons and dark matter are strongly coupled at large scales (r > R₂₀₀), but the coupling between gas and dark matter density profiles fades near the core of halos (r < 0.3R₂₀₀). We then show that the correlation between halo profile and integrated quantities induces a radius-dependent additive bias in the profile observables of halos when halos are selected on properties other than their mass. We discuss the impact of this effect on cluster abundance and cross-correlation cosmology with multiwavelength cosmological surveys.

The ongoing monitoring of the Galactic center and Sgr A*, the central supermassive black hole, produces surprising and unexpected findings. This goes hand in hand with the technical evolution of ground- and space-based telescopes and instruments, but also with the progression of image filter techniques such as the Lucy–Richardson algorithm. As we continue to trace the members of the S cluster close to Sgr A* on their expected trajectory around the supermassive black hole, we present the finding of a new stellar source, which we call S4716. The newly found star orbits Sgr A* in about 4.0 yr and can be detected with NIRC2 (Keck), OSIRIS (Keck), SINFONI (VLT), NACO (VLT), and GRAVITY (VLTI). With a periapse distance of about 100 au, S4716 shows an equivalent distance toward Sgr A* as S4711. These fast-moving stars undergo a similar dynamical evolution, since S4711–S4716 share comparable orbital properties. We will furthermore draw a connection between the recent finding of a new faint star called S300 and the data presented here. Additionally, we observed a blend-star event with S4716 and another newly identified S star S148 in 2017.

We present an analysis of physical properties of 34 [O iii] emission-line galaxies (ELGs) at z = 3.254 ± 0.029 in the Extended Chandra Deep Field South (ECDFS). These ELGs are selected from deep narrow H₂S(1) and broad K_s imaging of 383 arcmin² obtained with CFHT/WIRCam. We construct spectral energy distributions (SEDs) from U to K_s to derive the physical properties of ELGs. These [O iii] ELGs are identified as starburst galaxies with strong [O iii] lines of L_OIII ∼ 10^42.6–10^44.2 erg s⁻¹ and have stellar masses of M_* ∼ 10^9.0–10^10.6M_⊙ and star formation rates of ∼10–210 M_⊙ yr⁻¹. Our results show that 24% of our sample galaxies are dusty with A_V > 1 mag and EW([O iii])_rest ∼ 70–500 Å, which are often missed in optically selected [O iii] ELG samples. Their rest-frame UV and optical morphologies from HST/ACS and HST/WFC3 deep imaging reveal that these [O iii] ELGs are mostly multiple-component systems (likely mergers) or compact. And 20% of them are nearly invisible in the rest-frame UV owing to heavy dust attenuation. Interestingly, we find that our sample ELGs reside in an overdensity consisting of two components: one southeast (SE) with an overdensity factor of δ_gal ∼ 41 over a volume of 13³ cMpc³, and the other northwest (NW) with δ_gal ∼ 38 over a volume of 10³ cMpc³. The two overdense substructures are expected to be virialized at z = 0 with a total mass of ∼ 1.1 × 10¹⁵M_⊙ and ∼ 4.8 × 10¹⁴M_⊙ and probably merge into a Coma-like galaxy cluster.

At cosmic dawn, the 21 cm signal from intergalactic hydrogen was driven by Ly-α photons from some of the earliest stars, producing a spatial pattern that reflected the distribution of galaxies at that time. Due to the large foreground, it is thought that at around redshift 20 it is only observationally feasible to detect 21 cm fluctuations statistically, yielding a limited indirect probe of early galaxies. Here, we show that 21 cm images at cosmic dawn should actually be dominated by large (tens of comoving megaparsecs) high-contrast bubbles surrounding individual galaxies. We demonstrate this using a substantially upgraded seminumerical simulation code that realistically captures the formation and 21 cm effects of the small galaxies expected during this era. Small number statistics associated with the rarity of early galaxies, combined with the multiple scattering of photons in the blue wing of the Ly-α line, create the large bubbles, and also enhance the 21 cm power spectrum by a factor of 2–7 and add to it a feature that measures the typical brightness of galaxies. These various signatures of discrete early galaxies are potentially detectable with planned experiments, such as the Square Kilometer Array and the Hydrogen Epoch of Reionization Array, even if the early stars prove to be formed in dark matter halos with masses as low as 10⁸M_⊙, 10,000 times smaller than the Milky Way halo.

We find evidence for the first observation of the parametric decay instability (PDI) in the lower solar atmosphere. In particular, we find that the power spectrum of density fluctuations near the solar transition region resembles the power spectrum of the velocity fluctuations but with the frequency axis scaled up by about a factor of 2. These results are from an analysis of the Si iv lines observed by the Interface Region Imaging Spectrometer in the transition region of a polar coronal hole. We also find that the density fluctuations have radial velocity of about 75 km s⁻¹ and that the velocity fluctuations are much faster with an estimated speed of 250 km s⁻¹, as is expected for sound waves and Alfvén waves, respectively, in the transition region. Theoretical calculations show that this frequency relationship is consistent with those expected from PDI for the plasma conditions of the observed region. These measurements suggest an interaction between sound waves and Alfvén waves in the transition region, which is evidence for the parametric decay instability.

Thomson-scattered photospheric light is the dominant constituent of the lower solar corona’s spectral continuum viewed off-limb at optical wavelengths. Known as the K-corona, it is also linearly polarized. We investigate the possibility of using the a priori polarized characteristics of the K-corona, together with polarized emission lines, to measure and correct instrument-induced polarized crosstalk. First we derive the Stokes parameters of the Thomson scattering of unpolarized light in an irreducible spherical tensor formalism. This allows forward synthesis of the Thomson-scattered signal for the more complex scenario that includes symmetry-breaking features in the incident radiation field, which could limit the accuracy of our proposed technique. For this, we make use of an advanced 3D radiative magnetohydrodynamic coronal model. Together with synthesized polarized signals in the Fe xiii 10746 Å emission line, we find that an ad hoc correction of telescope- and instrument-induced polarization crosstalk is possible under the assumption of a nondepolarizing optical system.

While β Pic is known to host silicates in ring-like structures, whether the properties of these silicate dust vary with stellocentric distance remains an open question. We re-analyze the β Pictoris debris disk spectrum from the Spitzer Infrared Spectrograph (IRS) and a new Infrared Telescope Facility Spectrograph and Imager spectrum to investigate trends in Fe/Mg ratio, shape, and crystallinity in grains as a function of wavelength, a proxy for stellocentric distance. By analyzing a re-calibrated and re-extracted spectrum, we identify a new 18 μm forsterite emission feature and recover a 23 μm forsterite emission feature with a substantially larger line-to-continuum ratio than previously reported. We find that these prominent spectral features are primarily produced by small submicron-sized grains, which are continuously generated and replenished from planetesimal collisions in the disk and can elucidate their parent bodies’ composition. We discover three trends about these small grains: as stellocentric distance increases, (1) small silicate grains become more crystalline (less amorphous), (2) they become more irregular in shape, and (3) for crystalline silicate grains, the Fe/Mg ratio decreases. Applying these trends to β Pic’s planetary architecture, we find that the dust population exterior to the orbits of β Pic b and c differs substantially in crystallinity and shape. We also find a tentative 3–5 μm dust excess due to spatially unresolved hot dust emission close to the star. From our findings, we infer that the surfaces of large planetesimals are more Fe-rich and collisionally processed closer to the star but more Fe-poor and primordial farther from the star.

Episodic ejections of blobs (episodic jets) are widely observed in black hole sources and usually associated with flares. In this paper, by performing and analyzing three-dimensional general relativity magnetohydrodynamical numerical simulations of accretion flows, we investigate their physical mechanisms. We find that magnetic reconnection occurs in the accretion flow, likely due to the turbulent motion and differential rotation of the accretion flow, resulting in flares and formation of flux ropes. Flux ropes formed inside of 10–15 gravitational radii are found to mainly stay within the accretion flow, while flux ropes formed beyond this radius are ejected outward by magnetic forces and form the episodic jets. These results confirm the basic scenario proposed in Yuan et al. Moreover, our simulations find that the predicted velocity of the ejected blobs is in good consistency with observations of Sgr A*, M81, and M87. All of the processes were found to occur quasiperiodically, with the period being the orbital time at the radius where the flux rope is formed. The predicted period of the flares and ejections is consistent with those found from the light curves or image of Sgr A*, M87, and PKS 1510–089. The possible applications to protostellar accretion systems are discussed.

We study anisotropic magnetohydrodynamic (MHD) turbulence in the slow solar wind measured by Parker Solar Probe (PSP) and Solar Orbiter (SolO) during its first orbit from the perspective of variance anisotropy and correlation anisotropy. We use the Belcher & Davis approach (M1) and a new method (M2) that decomposes a fluctuating vector into parallel and perpendicular fluctuating vectors. M1 and M2 calculate the transverse and parallel turbulence components relative to the mean magnetic field direction. The parallel turbulence component is regarded as compressible turbulence, and the transverse turbulence component as incompressible turbulence, which can be either Alfvénic or 2D. The transverse turbulence energy is calculated from M1 and M2, and the transverse correlation length from M2. We obtain the 2D and slab turbulence energy and the corresponding correlation lengths from those transverse turbulence components that satisfy an angle between the mean solar wind flow speed and mean magnetic field θ_UB of either (i) 65° < θ_UB < 115° or (ii) 0° < θ_UB < 25° (155° < θ_UB < 180°), respectively. We find that the 2D turbulence component is not typically observed by PSP near perihelion, but the 2D component dominates turbulence in the inner heliosphere. We compare the detailed theoretical results of a nearly incompressible MHD turbulence transport model with the observed results of PSP and SolO measurements, finding good agreement between them.

Fast Radio Bursts (FRBs) are extragalactic radio transients that exhibit a distance-dependent dispersion of their signal, and thus can be used as cosmological probes. In this article we, for the first time, apply a model-independent approach to measure reionization from synthetic FRB data assuming these signals are detected beyond redshift 5. This method allows us to constrain the full shape of the reionization history as well as the CMB optical depth τ while avoiding the problems of commonly used model-based techniques. A total of 100 localized FRBs, originating from redshifts 5–15, could constrain (at 68% confidence level) the CMB optical depth to within 11%, and the midpoint of reionization to 4%, surpassing current state-of-the-art CMB bounds and quasar limits. Owing to the higher numbers of expected FRBs at lower redshifts, the τ constraints are asymmetric (+14%, −7%), providing a much stronger lower limit. Finally, we show that the independent constraints on reionization from FRBs will improve limits on other cosmological parameters, such as the amplitude of the power spectrum of primordial fluctuations.

Known sources of lithium (Li) in the universe include the Big Bang, novae, asymptotic giant branch stars, and cosmic-ray spallation. During their longer-lived evolutionary phases, stars are not expected to add to the Li budget of the Galaxy, but to largely deplete it. In this context, recent analyses of Li data from GALAH and LAMOST for field red clump (RC) stars have concluded that there is the need for a new production channel of Li, ubiquitous among low-mass stars, and that would be triggered on the upper red giant branch (RGB) or at helium ignition. This is distinct from the Li-rich giant problem and reflects bulk RC star properties. We provide an analysis of the GALAH Li data that accounts for the distribution of progenitor masses of field RC stars observed today. Such progenitors are different than today’s field RGB stars. Using standard post-main-sequence stellar evolution, we show that the distribution of Li among field RC giants as observed by GALAH is consistent with standard model predictions, and does not require new Li production mechanisms. Our model predicts a large fraction of very low Li abundances from low-mass progenitors, with higher abundances from higher mass ones. Moreover, there should be a large number of upper limits for RC giants, and higher abundances should correspond to higher masses. The most recent GALAH data indeed confirm the presence of large numbers of upper limits, and a much lower mean Li abundance in RC stars, in concordance with our interpretation.

The filamentary network of intergalactic medium (IGM) gas that gives origin to the Lyα forest in the spectra of distant quasars encodes information on the physics of structure formation and the early thermodynamics of diffuse baryonic material. Here we use a massive suite of more than 400 high-resolution cosmological hydrodynamical simulations run with the Graphics Processing Unit–accelerated code Cholla to study the IGM at high spatial resolution maintained over the entire computational volume. The simulations capture a wide range of possible IGM thermal histories by varying the photoheating and photoionizing background produced by star-forming galaxies and active galactic nuclei. A statistical comparison of synthetic spectra with the observed 1D flux power spectra of hydrogen at redshifts 2.2 ≤ z ≤ 5.0 and with the helium Lyα opacity at redshifts 2.4 < z < 2.9 tightly constrains the photoionization and photoheating history of the IGM. By leveraging the constraining power of the available Lyα forest data to break model degeneracies, we find that the IGM experienced two main reheating events over 1.2 Gyr of cosmic time. For our best-fit model, hydrogen reionization completes by z_R ≈ 6.0 with a first IGM temperature peak of T₀ ≃ 1.3 × 10⁴ K and is followed by the reionization of He ii that completes by z_R ≈ 3.0 and yields a second temperature peak of T₀ ≃ 1.4 × 10⁴ K. We discuss how our results can be used to obtain information on the timing and the sources of hydrogen and helium reionization.

This is the fourth paper exploring the infrared properties of giant H ii regions with the FORCAST instrument on the Stratospheric Observatory For Infrared Astronomy (SOFIA). Our survey utilizes the census of 56 Milky Way giant H ii regions identified by Conti & Crowther, and in this paper we present the 20 and 37 μm imaging data we obtained from SOFIA for sources Sgr D and W42. Based upon the SOFIA data and other multiwavelength data, we derive and discuss the detailed physical properties of the individual compact sources and subregions as well as the large-scale properties of Sgr D and W42. However, improved measurements have revealed much closer distances to both regions than previously believed, and consequently, both sources are not powerful enough to be considered giant H ii regions any longer. Motivated by this, we revisit the census of giant H ii regions, performing a search of the last two decades of literature to update each source with the most recent and/or most accurate distance measurements. Based on these new distance estimates, we determine that 14 sources in total (25%) are at sufficiently reliable and closer distances that they are not powerful enough to be considered giant H ii regions. We briefly discuss the observational and physical characteristics specific to Sgr D and W42 and show that they have properties distinct from the giant H ii regions previously studied as a part of this survey.

Although it is generally accepted that massive galaxies form in a two-phased fashion, beginning with a rapid mass buildup through intense starburst activities followed by primarily dry mergers that mainly deposit stellar mass at outskirts, the late time stellar mass growth of brightest cluster galaxies (BCGs), the most massive galaxies in the universe, is still not well understood. Several independent measurements have indicated a slower mass growth rate than predictions from theoretical models. We attempt to resolve the discrepancy by measuring the frequency of BCGs with multiple cores, which serve as a proxy of the merger rates in the central region and facilitate a more direct comparison with theoretical predictions. Using 79 BCGs at z = 0.06–0.15 with integral field spectroscopic data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) project, we obtain a multiple-core fraction of 0.11 ± 0.04 at z ≈ 0.1 within an 18 kpc radius from the center, which is comparable to the value of 0.08 ± 0.04 derived from mock observations of 218 simulated BCGs from the cosmological hydrodynamical simulation IllustrisTNG. We find that most cores that appear close to the BCGs from imaging data turn out to be physically associated systems. Anchoring on the similarity in the multiple-core frequency between the MaNGA and IllustrisTNG, we discuss the mass growth rate of BCGs over the past 4.5 Gyr.

A set of simulations with a 3D global climate model are performed to investigate the roles of obliquity and rotation period in the habitability of Earthlike exoplanets. The simulations cover the obliquity–rotation parameter space, from 0° to 90° in obliquity and 1–128 days in rotation period. The simulated global mean temperatures are warmest at 45° obliquity with fast rotations, due to the modification of the greenhouse effect from the spatial redistribution of clouds and water vapor. The slow-moving insolation–cloud mechanism, previously found in simulations with slow rotations and zero obliquity, also produces a cooling trend from intermediate obliquity to high obliquity, with the coldest climate occurring at 90° obliquity for all rotation periods. At low obliquities and fast rotation, persistent snow and sea ice can form, producing cooler temperatures. A Climate Habitability metric is defined, based on temperature and precipitation, which compares well with observations when applied to a simulation using Earth’s obliquity and rotation. Over a wider range of obliquity and rotation period, the Climate Habitability ranges from 10% to 70% of the terrestrial area. Overall, the simulated global mean surface temperature shows a much larger spread across the range of simulated rotation periods at 45° obliquity compared to 0° obliquity. Therefore, we conclude that 3D exoplanet simulations using intermediate obliquities (e.g., 45°) instead of 0° will reveal a wider range of possible climate conditions for specific orbital configurations. In addition, Earth’s climate habitability can increase by 25% if the obliquity increases from 235 to 45°.

Water worlds have been hypothesized as an alternative to photoevaporation in order to explain the gap in the radius distribution of Kepler exoplanets. We explore water worlds within the framework of a joint mass–radius–period distribution of planets fit to a sample of transiting Kepler exoplanets, a subset of which have radial velocity mass measurements. We employ hierarchical Bayesian modeling to create a range of ten mixture models that include multiple compositional subpopulations of exoplanets. We model these subpopulations—including planets with gaseous envelopes, evaporated rocky cores, evaporated icy cores, intrinsically rocky planets, and intrinsically icy planets—in different combinations in order to assess which combinations are most favored by the data. Using cross-validation, we evaluate the support for models that include planets with icy compositions compared to the support for models that do not, finding broad support for both. We find significant population-level degeneracies between subpopulations of water worlds and planets with primordial envelopes. Among models that include one or more icy-core subpopulations, we find a wide range for the fraction of planets with icy compositions, with a rough upper limit of 50%. Improved data sets or alternative modeling approaches may be able to better distinguish between these subpopulations of planets.

We report the first detection of deuterated water (HDO) toward an extragalactic hot core. The HDO 2₁₁–2₁₂ line has been detected toward hot cores N 105–2 A and 2 B in the N 105 star-forming region in the low-metallicity Large Magellanic Cloud (LMC) dwarf galaxy with the Atacama Large Millimeter/submillimeter Array (ALMA). We have compared the HDO line luminosity (L_HDO) measured toward the LMC hot cores to those observed toward a sample of 17 Galactic hot cores covering three orders of magnitude in L_HDO, four orders of magnitude in bolometric luminosity (L_bol), and a wide range of Galactocentric distances (thus metallicities). The observed values of L_HDO for the LMC hot cores fit very well into the L_HDO trends with L_bol and metallicity observed toward the Galactic hot cores. We have found that L_HDO seems to be largely dependent on the source luminosity, but metallicity also plays a role. We provide a rough estimate of the H₂O column density and abundance ranges toward the LMC hot cores by assuming that HDO/H₂O toward the LMC hot cores is the same as that observed in the Milky Way; the estimated ranges are systematically lower than Galactic values. The spatial distribution and velocity structure of the HDO emission in N 105–2 A is consistent with HDO being the product of the low-temperature dust grain chemistry. Our results are in agreement with the astrochemical model predictions that HDO is abundant regardless of the extragalactic environment and should be detectable with ALMA in external galaxies.

Supernovae of Type Iax (SNe Iax) are an accepted faint subclass of hydrogen-free supernovae. Their origin, the nature of the progenitor systems, however, is an open question. Recent studies suggest that the weak deflagration explosion of a near-Chandrasekhar-mass white dwarf in a binary system with a helium-star donor could be the origin of SNe Iax. In this scenario, the helium-star donor is expected to survive the explosion. We use the one-dimensional stellar evolution codes MESA and Kepler to follow the postimpact evolution of the surviving helium companion stars. The stellar models are based on our previous hydrodynamical simulations of ejecta–donor interaction, and we explore the observational characteristics of these surviving helium companions. We find that the luminosities of the surviving helium companions increase significantly after the impact: they could vary from 2500 L_⊙ to 16,000 L_⊙ for a Kelvin–Helmholtz timescale of about 10⁴ yr. After the star reaches thermal equilibrium, it evolves as an O-type hot subdwarf (sdO) star and continues its evolution along the evolutionary track of a normal sdO star with the same mass. Our results will help to identify the surviving helium companions of SNe Iax in future observations and to place new constraints on their progenitor models.

Analyzing the evolution of magnetic helicity flux at different atmospheric heights is key for identifying its role in the dynamics of active regions (ARs). The three-dimensional (3D) magnetic field of both flaring and nonflaring ARs is constructed using potential field extrapolations, enabling the derivation of emergence, shearing, and total magnetic helicity components at a range of atmospheric heights. An analysis of temporal oscillations of the derived components shows that the largest significant period of the three helicity fluxes are common (within ±2 hr) from the photosphere up to at least 1 Mm for flaring ARs—being consistent with the presence of a coupled oscillatory behavior that is absent in the nonflaring ARs. We suggest that large, energetic solar eruptions may have been produced in ARs when the vertical and horizontal helicity flux components became a coupled oscillatory system in the low solar atmosphere.

Using 2D particle-in-cell (PIC) simulations, the generation of electrostatic solitary waves (ESWs) and the associated plasma waves in symmetric magnetic reconnection are studied, and multiple kinds of ESWs with different propagating speeds are identified. Near the current sheet in the outflow region, there are two kinds of ESWs propagating away from the X line: their propagating speeds are about 0.73V_Te0 and 1.2V_Te0 (where V_Te0 is the initial electron thermal velocity), and their generation is associated with the Buneman instability and the electron two-stream instability, respectively. In the separatrix region, there is one kind of ESW propagating toward the X line with a propagating speed of about 1.2 V_Te0, which is formed during the nonlinear evolution of the electron two-stream instability. We also run a case with a guide field, and there exist two kinds of ESWs: the ESWs propagating away from the X line can be generated near the separatrices with electron outflow, while the ESWs propagating toward the X line can be generated near the separatrices with electron inflow. The two kinds of ESWs are associated with the electron two-stream instability and the Buneman instability, respectively.

Coronal mass ejections (CMEs) are associated with the eruption of magnetic flux ropes (MFRs), which usually appear as hot channels in active regions and coronal cavities in quiet-Sun regions. CMEs often exhibit a classical three-part structure in the lower corona when imaged with white-light coronagraphs, including a bright front, dark cavity, and bright core. For several decades, the bright core and dark cavity have been regarded as the erupted prominence and MFR, respectively. However, recent studies have clearly demonstrated that both the prominence and hot-channel MFR can be observed as the CME core. The current research presents a three-part CME resulting from the eruption of a coronal prominence cavity on 2010 October 7, with observations from two vantage perspectives, i.e., edge-on from the Earth and face-on from the Solar Terrestrial Relations Observatory (STEREO). Our observations illustrate two important results: (1) for the first time, the erupting coronal cavity is recorded as a channel-like structure in the extreme-ultraviolet passband, analogous to the hot-channel morphology, and is dubbed as the warm channel; and (2) both the prominence and warm-channel MFR (coronal cavity) in the extreme-ultraviolet passbands evolve into the CME core in the white-light coronagraphs of STEREO-A. The results suggest that we are working toward a unified explanation for the three-part structure of CMEs, in which both prominences and MFRs (hot or warm channels) are responsible for the bright core.

We perform comprehensive temporal and spectral analysis of the newly discovered X-ray transient MAXI J1803–298 using an AstroSat target of opportunity observation on 2021 May 11 during its outburst. The source was found to be in the hard-intermediate state. We detect type C quasi-periodic oscillations (QPOs) at the frequencies of ∼5.4 and ∼6.3 Hz along with a subharmonic at ∼2.8 Hz in the 3–15 keV band. The frequency and fractional rms amplitude of the QPO in the 15–30 keV band are found to be higher than those in the 3–15 keV band. We find soft lags of ∼3.8 and ∼6.8 ms for the respective QPOs at ∼5.4 and ∼6.3 Hz, whereas a soft lag of ∼4.7 ms is found at the subharmonic frequency. The increase in the soft lags at the QPO frequencies with energy is also observed in other black hole transients and attributed to the inclination dependence of the lags. The rms energy spectra indicate the power-law component to be more variable than the disk and reflection components. We find a broad iron line with an equivalent width of ∼0.17–0.19 keV and a reflection hump above ∼12 keV in the energy spectrum. Based on the X-ray spectroscopy and considering the distance to the source as 8 kpc, the estimated mass (∼8.5–16 M_⊙) and spin (a ≳ 0.7) of the black hole suggest that the source is likely to be a stellar mass Kerr black hole X-ray binary.

Changing-look active galactic nuclei (AGNs) present an important laboratory to understand the origin and physical properties of the broad-line region (BLR). We investigate follow-up optical spectroscopy spanning ∼500 days after the outburst of the changing-look AGN 1ES 1927+654. The emission lines displayed dramatic, systematic variations in intensity, velocity width, velocity shift, and symmetry. Analysis of optical spectra and multiband images indicates that the host galaxy contains a pseudobulge and a total stellar mass of . Enhanced continuum radiation from the outburst produced an accretion disk wind, which condensed into BLR clouds in the region above and below the temporary eccentric disk. Broad Balmer lines emerged ∼100 days after the outburst, together with an unexpected, additional component of narrow-line emission. The newly formed BLR clouds then traveled along a similar eccentric orbit (e ≈ 0.6). The Balmer decrement of the BLR increased by a factor of ∼4–5 as a result of secular changes in cloud density. The drop in density at late times allowed the production of He i and He ii emission. The mass of the black hole cannot be derived from the broad emission lines because the BLR is not virialized. Instead, we use the stellar properties of the host galaxy to estimate . The nucleus reached near or above its Eddington limit during the peak of the outburst. We discuss the nature of the changing-look AGN 1ES 1927+654 in the context of other tidal disruption events.

Astrophysical jets are often observed as bent or curved structures. We also know that the different jet sources may be binary in nature, which may lead to a regular, periodic motion of the jet nozzle, an orbital motion, or precession. Here we present the results of 2D (M)HD simulations in order to investigate how a precessing or orbiting jet nozzle affects the propagation of a high-speed jet. We have performed a parameter study of systems with different precession angles, different orbital periods or separations, and different magnetic field strengths. We find that these kinds of nozzles lead to curved jet propagation, which is determined by the main parameters that define the jet nozzle. We find C-shaped jets from orbiting nozzles and S-shaped jets from precessing nozzles. Over a long time and long distances, the initially curved jet motion bores a broad channel into the ambient gas that is filled with high-speed jet material whose lateral motion is damped, however. A strong (longitudinal) magnetic field can damp the jet curvature that is enforced by either precession or orbital motion of the jet sources. We have investigated the force balance across the jet and ambient medium and found that the lateral magnetic pressure and gas pressure gradients are almost balanced, but that a lack of gas pressure on the concave side of the curvature is leading to the lateral motion. Magnetic tension does not play a significant role. Our results are obtained in code units, but we provide scaling relations such that our results may be applied to young stars, microquasars, symbiotic stars, or active galactic nuclei.

Interchange reconnection is thought to play an important role in determining the dynamics and material composition of the slow solar wind that originates from near coronal-hole boundaries. To explore the implications of this process we simulate the dynamic evolution of a solar wind stream along a newly-opened magnetic flux tube. The initial condition is composed of a piecewise continuous dynamic equilibrium in which the regions above and below the reconnection site are extracted from steady-state solutions along open and closed field lines. The initial discontinuity at the reconnection site is highly unstable and evolves as a Riemann problem, decomposing into an outward-propagating shock and inward-propagating rarefaction that eventually develop into a classic N-wave configuration. This configuration ultimately propagates into the heliosphere as a coherent structure and the entire system eventually settles to a quasi-steady wind solution. In addition to simulating the fluid evolution we also calculate the time-dependent non-equilibrium ionization of oxygen in real time in order to construct in situ diagnostics of the conditions near the reconnection site. This idealized description of the plasma dynamics along a newly-opened magnetic field line provides a baseline for predicting and interpreting the implications of interchange reconnection for the slow solar wind. Notably, the density and velocity within the expanding N-wave are generally enhanced over the ambient wind, as is the O⁷⁺/O⁶⁺ ionization ratio, which exhibits a discontinuity across the reconnection site that is transported by the flow and arrives later than the propagating N-wave.

Particle acceleration during magnetic reconnection is a long-standing topic in space, solar, and astrophysical plasmas. Recent 3D particle-in-cell simulations of magnetic reconnection show that particles can leave flux ropes due to 3D field-line chaos, allowing particles to access additional acceleration sites, gain more energy through Fermi acceleration, and develop a power-law energy distribution. This 3D effect does not exist in traditional 2D simulations, where particles are artificially confined to magnetic islands due to their restricted motions across field lines. Full 3D simulations, however, are prohibitively expensive for most studies. Here, we attempt to reproduce 3D results in 2D simulations by introducing ad hoc pitch-angle scattering to a small fraction of the particles. We show that scattered particles are able to transport out of 2D islands and achieve more efficient Fermi acceleration, leading to a significant increase of energetic particle flux. We also study how the scattering frequency influences the nonthermal particle spectra. This study helps achieve a complete picture of particle acceleration in magnetic reconnection.

We perform particle-in-cell simulations to elucidate the microphysics of relativistic weakly magnetized shocks loaded with electron-positron pairs. Various external magnetizations σ ≲ 10⁻⁴ and pair-loading factors Z_± ≲ 10 are studied, where Z_± is the number of loaded electrons and positrons per ion. We find the following: (1) The shock becomes mediated by the ion Larmor gyration in the mean field when σ exceeds a critical value σ_L that decreases with Z_±. At σ ≲ σ_L the shock is mediated by particle scattering in the self-generated microturbulent fields, the strength and scale of which decrease with Z_±, leading to lower σ_L. (2) The energy fraction carried by the post-shock pairs is robustly in the range between 20% and 50% of the upstream ion energy. The mean energy per post-shock electron scales as . (3) Pair loading suppresses nonthermal ion acceleration at magnetizations as low as σ ≈ 5 × 10⁻⁶. The ions then become essentially thermal with mean energy , while electrons form a nonthermal tail, extending from to . When σ = 0, particle acceleration is enhanced by the formation of intense magnetic cavities that populate the precursor during the late stages of shock evolution. Here, the maximum energy of the nonthermal ions and electrons keeps growing over the duration of the simulation. Alongside the simulations, we develop theoretical estimates consistent with the numerical results. Our findings have important implications for models of early gamma-ray burst afterglows.

We study time-dependent relativistic jets under the influence of the radiation field of the accretion disk. The accretion disk consists of an inner compact corona and an outer sub-Keplerian disk. The thermodynamics of the fluid is governed by a relativistic equation of state (EOS) for multispecies fluid that enables us to study the effect of composition on jet dynamics. Jets originate from the vicinity of the central black hole, where the effect of gravity is significant and traverses large distances where only special relativistic treatment is sufficient. So we have modified the flat metric to include the effect of gravity. In this modified relativistic framework we have developed a new total variation diminishing routine along with a multispecies EOS for the purpose. We show that the acceleration of jets crucially depends on flow composition. All the results presented are transonic in nature; starting from very low injection velocities, the jets can achieve high Lorentz factors. For sub-Eddington luminosities, lepton-dominated jets can be accelerated to Lorentz factors >50. The change in radiation field due to variation in the accretion disk dynamics will be propagated to the jet in a finite amount of time. Hence, any change in radiation field due to a change in disk configuration will affect the lower part of the jet before it affects the outer part. This can drive shock transition in the jet flow. Depending on the disk oscillation frequency, amplitude, and jet parameters, these shocks can collide with each other and may trigger shock cascades.

We present GaiaHub, a publicly available tool that combines Gaia measurements with Hubble Space Telescope (HST) archival images to derive proper motions (PMs). It increases the scientific impact of both observatories beyond their individual capabilities. Gaia provides PMs across the whole sky, but the limited mirror size and time baseline restrict the best PM performance to relatively bright stars. HST can measure accurate PMs for much fainter stars over a small field, but this requires two epochs of observation, which are not always available. GaiaHub yields considerably improved PM accuracy compared to Gaia-only measurements, especially for faint sources (G ≳ 18), requiring only a single epoch of HST data observed more than ∼7 yr ago (before 2012). This provides considerable scientific value, especially for dynamical studies of stellar systems or structures in and beyond the Milky Way (MW) halo, for which the member stars are generally faint. To illustrate the capabilities and demonstrate the accuracy of GaiaHub, we apply it to samples of MW globular clusters (GCs) and classical dwarf spheroidal (dSph) satellite galaxies. This allows us, e.g., to measure the velocity dispersions in the plane of the sky for objects out to and beyond ∼100 kpc. We find, on average, mild radial velocity anisotropy in GCs, consistent with existing results for more nearby samples. We observe a correlation between the internal kinematics of the clusters and their ellipticity, with more isotropic clusters being, on average, more round. Our results also support previous findings that Draco and Sculptor dSph galaxies appear to be radially anisotropic systems.

The Serpens Molecular Cloud is one of the most active star-forming regions within 500 pc, with over 1000 young stellar objects (YSOs) at different evolutionary stages. The ages of the member stars inform us about the star formation history of the cloud. In this paper, we develop a spectral energy distribution (SED) fitting method for nearby evolved (diskless) young stars from members of the Pleiades to estimate their ages, with a temperature scale adopted from APOGEE spectra. When compared with literature temperatures of selected YSOs in Orion, the SED fits to cool (<5000 K) stars have temperatures that differ by an average of ≲50 K and have a scatter of ∼210 K for both disk-hosting and diskless stars. We then apply this method to YSOs in the Serpens Molecular Cloud to estimate ages of optical members previously identified from Gaia DR2 astrometry data. The optical members in Serpens are concentrated in different subgroups with ages from ∼4 to ∼22 Myr; the youngest clusters, W40 and Serpens South, are dusty regions that lack enough optical members to be included in this analysis. These ages establish that the Serpens Molecular Cloud has been forming stars for much longer than has been inferred from infrared surveys.

Recent precise measurements of primary and secondary cosmic-ray (CR) species in the teravolt rigidity domain have unveiled a bump in their spectra, located between 0.5 and 50 TV. We argue that a local shock may generate such a bump by increasing the rigidity of the preexisting CRs below 50 TV by a mere factor of ∼1.5. Reaccelerated particles below ∼0.5 TV are convected with the interstellar medium flow and do not reach the Sun, thus creating the bump. This single universal process is responsible for the observed spectra of all CR species in the rigidity range below 100 TV. We propose that one viable shock candidate is the Epsilon Eridani star at 3.2 pc from the Sun, which is well aligned with the direction of the local magnetic field. Other shocks, such as old supernova shells, may produce a similar effect. We provide a simple formula, Equation (9), that reproduces the spectra of all CR species with only two nonadjustable shock parameters, uniquely derived from the proton data. We show how our formalism predicts helium and carbon spectra and the B/C ratio.

The complexity of atmospheric retrieval models is largely data-driven, and one-dimensional models have generally been considered adequate with current data quality. However, recent studies have suggested that using 1D models in retrievals can result in anomalously cool terminator temperatures and biased abundance estimates even with existing transmission spectra of hot Jupiters. Motivated by these claims and upcoming high-quality transmission spectra, we systematically explore the limitations of 1D models using synthetic and current observations. We use 1D models of varying complexity, both analytic and numerical, to revisit claims of biases when interpreting transmission spectra of hot Jupiters with inhomogeneous terminator compositions. Overall, we find the reported biases to be resulting from specific model assumptions rather than intrinsic limitations of 1D atmospheric models in retrieving current observations of asymmetric terminators. Additionally, we revise atmospheric retrievals of the hot Jupiter WASP-43b (T_eq = 1440 K) and the ultra-hot Jupiter WASP-103b (T_eq = 2484 K), for which previous studies inferred abnormally cool atmospheric temperatures. We retrieve temperatures consistent with expectations. We note, however, that in the limit of extreme terminator inhomogeneities and high data quality, some atmospheric inferences may conceivably be biased—although to a lesser extent than previously claimed. To address such cases, we implement a 2D retrieval framework for transmission spectra that allows accurate constraints on average atmospheric properties and provides insights into the spectral ranges where the imprints of atmospheric inhomogeneities are strongest. Our study highlights the need for careful considerations of model assumptions and data quality before attributing biases in retrieved estimates to unaccounted atmospheric inhomogeneities.

We recently extended our Parker-type transport equation for energetic particle interaction with numerous dynamic small-scale magnetic flux ropes (SMFRs) to include perpendicular diffusion in addition to parallel diffusion. We present a new analytical solution to this equation assuming heliocentric spherical geometry with spherical symmetry for all SMFR acceleration mechanisms present in the transport theory. With the goal of identifying the dominant mechanism(s) through which particles are accelerated by SMFRs, a search was launched to identify events behind interplanetary shocks that could be explained by our new solution and not classical diffusive shock acceleration. Two new SMFR acceleration events were identified in situ for the first time within heliocentric distances of 1 astronomical unit (au) in Helios A data. A Metropolis–Hastings algorithm is employed to fit the new solution to the energetic proton fluxes so that the relative strength of the transport coefficients associated with each SMFR acceleration mechanism can be determined. We conclude that the second-order Fermi mechanism for particle acceleration by SMFRs is more important than first-order Fermi acceleration due to the mean compression of the SMFRs regions during these new events. Furthermore, with the aid of SMFR parameters determined via the Grad–Shafranov reconstruction method, we find that second-order Fermi SMFR acceleration is dominated by the turbulent motional electric field parallel to the guide/background field. Finally, successful reproduction of energetic proton flux data during these SMFR acceleration events also required efficient particle escape from the SMFR acceleration regions.

The magnetorotational instability (MRI) has been extensively studied in circular magnetized disks, and its ability to drive accretion has been demonstrated in a multitude of scenarios. There are reasons to expect eccentric magnetized disks to also exist, but the behavior of the MRI in these disks remains largely uncharted territory. Here we present the first simulations that follow the nonlinear development of the MRI in eccentric disks. We find that the MRI in eccentric disks resembles circular disks in two ways, in the overall level of saturation and in the dependence of the detailed saturated state on magnetic topology. However, in contrast with circular disks, the Maxwell stress in eccentric disks can be negative in some disk sectors, even though the integrated stress is always positive. The angular momentum flux raises the eccentricity of the inner parts of the disk and diminishes the same of the outer parts. Because material accreting onto a black hole from an eccentric orbit possesses more energy than material tracing the innermost stable circular orbit, the radiative efficiency of eccentric disks may be significantly lower than circular disks. This may resolve the “inverse energy problem” seen in many tidal disruption events.

The Airborne Infrared Spectrometer (AIR-Spec) was commissioned during the 2017 total solar eclipse, when it observed five infrared coronal emission lines from a Gulfstream V research jet owned by the National Science Foundation and operated by the National Center for Atmospheric Research. The second AIR-Spec research flight took place during the 2019 July 2 total solar eclipse across the south Pacific. The 2019 eclipse flight resulted in seven minutes of observations, during which the instrument measured all four of its target emission lines: S xi 1.393 μm, Si x 1.431 μm, S xi 1.921 μm, and Fe ix 2.853 μm. The 1.393 μm S xi line was detected for the first time, and probable first detections were made of Si xi 1.934 μm and Fe x 1.947 μm. The 2017 AIR-Spec detection of Fe ix was confirmed and the first observations were made of the Fe ix line intensity as a function of solar radius. Telluric absorption features were used to calibrate the wavelength mapping, instrumental broadening, and throughput of the instrument. AIR-Spec underwent significant upgrades in preparation for the 2019 eclipse observation. The thermal background was reduced by a factor of 30, providing a 5.5× improvement in signal-to-noise ratio, and the postprocessed pointing stability was improved by a factor of 5 to <10″ rms. In addition, two imaging artifacts were identified and resolved, improving the spectral resolution and making the 2019 data easier to interpret.

We report the first unambiguous detection and mass measurement of an isolated stellar-mass black hole (BH). We used the Hubble Space Telescope (HST) to carry out precise astrometry of the source star of the long-duration (t_E ≃ 270 days), high-magnification microlensing event MOA-2011-BLG-191/OGLE-2011-BLG-0462 (hereafter designated as MOA-11-191/OGLE-11-462), in the direction of the Galactic bulge. HST imaging, conducted at eight epochs over an interval of 6 yr, reveals a clear relativistic astrometric deflection of the background star’s apparent position. Ground-based photometry of MOA-11-191/OGLE-11-462 shows a parallactic signature of the effect of Earth’s motion on the microlensing light curve. Combining the HST astrometry with the ground-based light curve and the derived parallax, we obtain a lens mass of 7.1 ± 1.3 M_⊙ and a distance of 1.58 ± 0.18 kpc. We show that the lens emits no detectable light, which, along with having a mass higher than is possible for a white dwarf or neutron star, confirms its BH nature. Our analysis also provides an absolute proper motion for the BH. The proper motion is offset from the mean motion of Galactic disk stars at similar distances by an amount corresponding to a transverse space velocity of ∼45 km s⁻¹, suggesting that the BH received a “natal kick” from its supernova explosion. Previous mass determinations for stellar-mass BHs have come from radial velocity measurements of Galactic X-ray binaries and from gravitational radiation emitted by merging BHs in binary systems in external galaxies. Our mass measurement is the first for an isolated stellar-mass BH using any technique.

We present the Local Volume Complete Cluster Survey (LoVoCCS; we pronounce it as “low-vox” or “law-vox,” with stress on the second syllable), an NSF’s National Optical-Infrared Astronomy Research Laboratory survey program that uses the Dark Energy Camera to map the dark matter distribution and galaxy population in 107 nearby (0.03 < z < 0.12) X-ray luminous ([0.1–2.4 keV] L_X500 > 10⁴⁴ erg s⁻¹) galaxy clusters that are not obscured by the Milky Way. The survey will reach Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) Year 1–2 depth (for galaxies r = 24.5, i = 24.0, signal-to-noise ratio (S/N) > 20; u = 24.7, g = 25.3, z = 23.8, S/N > 10) and conclude in ∼2023 (coincident with the beginning of LSST science operations), and will serve as a zeroth-year template for LSST transient studies. We process the data using the LSST Science Pipelines that include state-of-the-art algorithms and analyze the results using our own pipelines, and therefore the catalogs and analysis tools will be compatible with the LSST. We demonstrate the use and performance of our pipeline using three X-ray luminous and observation-time complete LoVoCCS clusters: A3911, A3921, and A85. A3911 and A3921 have not been well studied previously by weak lensing, and we obtain similar lensing analysis results for A85 to previous studies. (We mainly use A3911 to show our pipeline and give more examples in the Appendix.)

The CALorimetric Electron Telescope (CALET) on the International Space Station consists of a high-energy cosmic-ray CALorimeter (CAL) and a lower-energy CALET Gamma-ray Burst Monitor (CGBM). CAL is sensitive to electrons up to 20 TeV, cosmic-ray nuclei from Z = 1 through Z ∼ 40, and gamma rays over the range 1 GeV–10 TeV. CGBM observes gamma rays from 7 keV to 20 MeV. The combined CAL-CGBM instrument has conducted a search for gamma-ray bursts (GRBs) since 2015 October. We report here on the results of a search for X-ray/gamma-ray counterparts to gravitational-wave events reported during the LIGO/Virgo observing run O3. No events have been detected that pass all acceptance criteria. We describe the components, performance, and triggering algorithms of the CGBM—the two Hard X-ray Monitors consisting of LaBr₃(Ce) scintillators sensitive to 7 keV–1 MeV gamma rays and a Soft Gamma-ray Monitor BGO scintillator sensitive to 40 keV–20 MeV—and the high-energy CAL consisting of a charge detection module, imaging calorimeter, and the fully active total absorption calorimeter. The analysis procedure is described and upper limits to the time-averaged fluxes are presented.

The LIGO and Virgo gravitational-wave detectors have uncovered binary black hole systems with definitively nonzero spins, as well as systems with significant spin residing in the more massive black hole of the pair. We investigate the ability of isolated binary evolution in forming such highly spinning, asymmetric-mass systems through both accretion onto the first-born black hole and tidal spin-up of the second-born black hole using a rapid population synthesis approach with detailed considerations of spin-up through tidal interactions. Even with the most optimistic assumptions regarding the efficiency at which an accreting star receives material from a donor, we find that it is difficult to form systems with significant mass asymmetry and moderate or high spins in the primary black hole component. Assuming efficient angular momentum transport within massive stars and Eddington-limited accretion onto black holes, we find that >1.5% of systems in the underlying binary black hole population have a primary black hole spin greater than 0.2 and a mass asymmetry of greater than 2:1 in our most optimistic models, with most models finding that this criteria is only met in ∼0.01% of systems. The production of systems with significant mass asymmetries and spin in the primary black hole component is thus an unlikely byproduct of isolated evolution unless highly super-Eddington accretion is invoked or angular momentum transport in massive stars is less efficient than typically assumed.

Reionization is an inhomogeneous process, thought to begin in small ionized bubbles of the intergalactic medium (IGM) around overdense regions of galaxies. Recent Lyα studies during the epoch of reionization show evidence that ionized bubbles formed earlier around brighter galaxies, suggesting higher IGM transmission of Lyα from these galaxies. We investigate this problem using IR slitless spectroscopy from the Hubble Space Telescope (HST) Wide-Field Camera 3 (WFC3) G102 grism observations of 148 galaxies selected via photometric redshifts at 6.0 < z < 8.2. These galaxies have spectra extracted from the CANDELS Lyα Emission at Reionization (CLEAR) survey. We combine the CLEAR data for 275 galaxies with the Keck Deep Imaging Multi-Object Spectrograph and MOSFIRE data set from the Texas Spectroscopic Search for Lyα Emission at the End of Reionization Survey. We constrain the Lyα equivalent width (EW) distribution at 6.0 < z < 8.2, which is described by an exponential form, , with the characteristic e-folding scale width (W₀). We confirm a significant drop in the Lyα strength (i.e., W₀) at z > 6. Furthermore, we compare the redshift evolution of W₀ between galaxies at different UV luminosities. UV-bright (M_UV < −21 [i.e., L_UV > L*]) galaxies show weaker evolution with a decrease of 0.4 ( ± 0.2) dex in W₀ at z > 6, while UV-faint (M_UV > −21 [L_UV < L*]) galaxies exhibit a significant drop of 0.7–0.8 (±0.2) dex in W₀ from z < 6 to z > 6. If the change in W₀ is proportional to the change in the IGM transmission for Lyα photons, then this is evidence that the transmission is “boosted” around UV-brighter galaxies, suggesting that reionization proceeds faster in regions around such galaxies.

We analyze spatially resolved and co-added SDSS-IV MaNGA spectra with signal-to-noise ratio ∼100 from 2200 passive central galaxies (z ∼ 0.05) to understand how central galaxy assembly depends on stellar mass (M_*) and halo mass (M_h). We control for systematic errors in M_h by employing a new group catalog from Tinker and the widely used Yang et al. catalog. At fixed M_*, the strengths of several stellar absorption features vary systematically with M_h. Completely model-free, this is one of the first indications that the stellar populations of centrals with identical M_* are affected by the properties of their host halos. To interpret these variations, we applied full spectral fitting with the code alf. At fixed M_*, centrals in more massive halos are older, show lower [Fe/H], and have higher [Mg/Fe] with 3.5σ confidence. We conclude that halos not only dictate how much M_* galaxies assemble but also modulate their chemical enrichment histories. Turning to our analysis at fixed M_h, high-M_* centrals are older, show lower [Fe/H], and have higher [Mg/Fe] for M_h > 10¹² h⁻¹ M_⊙ with confidence >4σ. While massive passive galaxies are thought to form early and rapidly, our results are among the first to distinguish these trends at fixed M_h. They suggest that high-M_* centrals experienced unique early formation histories, either through enhanced collapse and gas fueling or because their halos were early forming and highly concentrated, a possible signal of galaxy assembly bias.

In supernovae (SNe), where the light curves show evidence of strong and early interaction between the ejecta and the circumstellar matter (CSM), the formation of new dust is estimated to take place in a dense shell of gas between the forward shock (FS) and the reverse shock (RS). For the first time, in this study the mechanism of dust formation in this dense shell is modeled. A set of nine cases, considering variations of the ejecta mass and the pre-explosion mass-loss rates, is considered, accounting for the diverse nature of interactions reported in such SNe. For a single main-sequence mass, the variation of ejecta mass was manifested as a variation of the H-shell mass of the star, lost due to pre-explosion mass loss. We find that the dust masses in the dense shell range between 10⁻³ and 0.8 M_⊙, composed of O-rich and C-rich grains, whose relative proportions are determined by the nature of interaction. Dust formation in the post-shock gas is characterized by a gradual production rate, mostly ranging from 10⁻⁶ to 10⁻³M_⊙ day⁻¹, which may continue for a decade, post-explosion. A higher mass-loss rate leads to a larger mass of dust, while a smaller ejecta mass (smaller leftover H shell) increases the efficiency of dust production in such SNe. Dust formed behind the RS, as in our calculations, is not subject to destruction by either the FS or RS and is thus likely to survive in a larger proportion than dust formed in the ejecta.

We present Atacama Large Millimeter/submillimeter Array data on the 3 mm continuum emission, CO isotopologues (¹²CO, ¹³CO, and C¹⁸O), and high-density molecular tracers (HCN, HCO⁺, HNC, HNCO, CS, CN, and CH₃OH) in NGC 4526. These data enable a detailed study of the physical properties of the molecular gas in a longtime resident of the Virgo Cluster; comparisons to more commonly studied spiral galaxies offer intriguing hints into the processing of molecular gas in the cluster environment. Many molecular line ratios in NGC 4526, along with our inferred abundances and CO/H₂ conversion factors, are similar to those found in nearby spirals. One striking exception is the very low observed ¹²CO/¹³CO(1−0) line ratio, 3.4 ± 0.3, which is unusually low for spirals though not for Virgo Cluster early-type galaxies. We carry out radiative transfer modeling of the CO isotopologues with some archival (2−1) data, and we use Bayesian analysis with Markov Chain Monte Carlo techniques to infer the physical properties of the CO-emitting gas. We find surprisingly low [¹²CO/¹³CO] abundance ratios of and at radii of 0.4 kpc and 1 kpc. The emission from the high-density tracers HCN, HCO⁺, HNC, CS, and CN is also relatively bright, and CN is unusually optically thick in the inner parts of NGC 4526. These features hint that processing in the cluster environment may have removed much of the galaxy’s relatively diffuse, optically thinner molecular gas along with its atomic gas. Angular momentum transfer to the surrounding intracluster medium may also have caused contraction of the disk, magnifying radial gradients such as we find in [¹³CO/C¹⁸O]. More detailed chemical evolution modeling would be interesting in order to explore whether the unusual [¹²CO/¹³CO] abundance ratio is entirely an environmental effect or whether it also reflects the relatively old stellar population in this early-type galaxy.

Using full Boltzmann neutrino transport, we performed 2D core-collapse supernova simulations in axisymmetry for two progenitor models with 11.2 and 15.0 M_⊙, both rotational and nonrotational. We employed the results obtained in the early post-bounce phase (t ≲ 20 ms) to assess performance under rapid rotation of some closure relations commonly employed in the truncated moment method. We first made a comparison in 1D under spherical symmetry, though, of the Eddington factor p defined in the fluid rest frame (FR). We confirmed that the maximum entropy closure for the Fermionic distribution (MEFD) performs better than others near the proto–neutron star surface, where p < 1/3 occurs, but does not work well even in 1D when the phase-space occupancy satisfies e < 0.5 together with p < 1/3, the condition known to be not represented by MEFD. For the 2D models with the rapid rotation, we employed the principal-axis analysis of the Eddington tensor. We paid particular attention to the direction of the longest principal axis. We observed in FR that it is aligned neither with the radial direction nor with the neutrino flux in 2D, particularly so in convective and/or rapidly rotating regions, the fact not accommodated in the moment method. We repeated the same analysis in the laboratory frame and found again that the direction of the longest principal axis is not well reproduced by MEFD because the interpolation between the optically thick and thin limits is not very accurate in this frame.

Stellar flares are characterized by sudden enhancement of electromagnetic radiation from the atmospheres of stars. Compared to their solar counterparts, our knowledge on the coronal plasma dynamics of stellar flares and their connection to coronal mass ejections remains very limited. With time-resolved high-resolution spectroscopic observations from the Chandra X-ray Observatory, we detected noticeable coronal plasma flows during several stellar flares on a nearby dMe star EV Lac. In the observed spectra of O viii (3 MK), Fe xvii (6 MK), Mg xii (10 MK), and Si xiv (16 MK) lines, these flare-induced upflows/downflows appear as significant Doppler shifts of several tens to 130 km s⁻¹ , and the upflow velocity generally increases with temperature. Variable line ratios of the Si xiii triplet reveal that this plasma flows in most flares are accompanied by an increase in the coronal plasma density and temperature. We interpret these results as X-ray evidence of chromospheric evaporation on EV Lac. In two successive flares, the plasma flow pattern and a sharp increase of the measured coronal density are highly suggestive of explosive evaporation. The transition from redshifts to blueshifts in such an explosive evaporation occurs at a temperature of at least 10 MK, much higher than that observed in solar flares (∼1 MK). However, in one flare the cool and warm upflows appear to be accompanied by a decreasing plasma density, which might be explained by a stellar filament/prominence eruption coupled to this flare. These results provide important clues to understanding the coronal plasma dynamics during flares on M dwarfs.

A number of double coronal X-ray sources have been observed during solar flares by RHESSI, where the two sources reside at different sides of the inferred reconnection site. However, where and how these X-ray-emitting electrons are accelerated remains unclear. Here we present the first model of the double coronal hard X-ray (HXR) sources, where electrons are accelerated by a pair of termination shocks driven by bidirectional fast reconnection outflows. We model the acceleration and transport of electrons in the flare region by numerically solving the Parker transport equation using velocity and magnetic fields from the macroscopic magnetohydrodynamic simulation of a flux rope eruption. We show that electrons can be efficiently accelerated by the termination shocks and high-energy electrons mainly concentrate around the two shocks. The synthetic HXR emission images display two distinct sources extending to >100 keV below and above the reconnection region, with the upper source much fainter than the lower one. The HXR energy spectra of the two coronal sources show similar spectral slopes, consistent with the observations. Our simulation results suggest that the flare termination shock can be a promising particle acceleration mechanism in explaining the double-source nonthermal emissions in solar flares.

We present the discovery of 17 double white dwarf (WD) binaries from our ongoing search for extremely low mass (ELM) < 0.3 M_⊙ WDs, objects that form from binary evolution. Gaia parallax provides a new means of target selection that we use to evaluate our original ELM Survey selection criteria. Cross-matching the Gaia and Sloan Digital Sky Survey (SDSS) catalogs, we identify an additional 36 ELM WD candidates with 17 < g < 19 mag and within the 3σ uncertainties of our original color selection. The resulting discoveries imply the ELM Survey sample was 90% complete in the color range −0.4 < (g − r)₀ < −0.1 mag (approximately 9000 K < T_eff < 22,000 K). Our observations complete the sample in the SDSS footprint. Two newly discovered binaries, J123950.370−204142.28 and J232208.733+210352.81, have orbital periods of 22.5 and 32 minutes, respectively, and are future Laser Interferometer Space Antenna gravitational-wave sources.

We present the fine structure of the inner solar corona between 1.65 and 3.0 solar radii as revealed by the STEREO-A COR1 white-light coronagraph from 2008 June 20 to July 31. The COR1 imaging data were wavelet processed to enhance the intensity contrast of coronal features. The constructed limb synoptic maps at a range of altitudes show the evolution in time and altitude of these fine structures within the streamer belt, and equatorial and polar coronal holes during this period near the solar minimum. Distinct streamer-stalk structures are seen embedded within a diffuse background of the helmet streamer belt, which are preserved as they extend to higher heights. Pseudostreamers are also seen as multiple stalk structures, which also continue to higher heights. Various polar plume structures are seen to last from hours to days. Similar plume structures are also seen within the corona subtended by equatorial coronal holes. We compare the COR1 maps to that of the magnetic topology revealed by the modeled squashing factors, and discuss the relation between the two types of maps and its implications in the context of solar wind formation.

Tidal disruption of stars in dense nuclear star clusters containing supermassive central black holes (SMBH) is modeled by high-accuracy direct N-body simulation. Stars getting too close to the SMBH are tidally disrupted, and a tidal disruption event (TDE) happens. The TDEs probe the properties of SMBHs, their accretion disks, and the surrounding nuclear stellar cluster. In this paper, we compare the rates of full tidal disruption events (FTDEs) with partial tidal disruption events (PTDEs). Since a PTDE does not destroy the star, a leftover object emerges; we use the term “leftover star” for it. Two novel effects occur in the simulation: (1) variation of the leftover star’s mass and radius and (2) variation of the leftover star’s orbital energy. After switching on these two effects in our simulation, the number of FTDEs is reduced by roughly 28%, and the reduction is mostly due to the ejection of the leftover stars from PTDEs originally coming from a relatively large distance. The number of PTDEs is about 75% higher than the simple estimation given by Stone et al., and the enhancement is mainly due to the multiple PTDEs produced by the leftover stars residing in the diffusive regime. We compute the peak mass fallback rate for the PTDEs and FTDEs recorded in the simulation and find that 58% of the PTDEs have a peak mass fallback rate exceeding the Eddington limit, and the number of super-Eddington PTDEs is 2.3 times the number of super-Eddington FTDEs.

Current sheets (CSs) are preferred sites of magnetic reconnection and energy dissipation in astrophysical plasmas. Electric currents in them may be carried by both electrons and ions. In our prior theoretical studies of the CS formation in turbulent plasmas, we utilized fully kinetic and hybrid code simulations with ions considered as particles and electrons—as a massless fluid. We found that electron-dominated CSs in which electrons become the main carriers of the electric current and contributors to energy dissipation may form inside or nearby ion-dominated CSs. These structures represent a distinguished type of CSs and should not be mixed up with so-called electron-scale CSs. Current simulations show that such CSs are characterized by the electron-to-ion bulk speed ratio (u_e/u_i) increases that can be seen at ion scales according to theoretical predictions and high-resolution observations from the Magnetospheric Multiscale mission. Therefore, applying the u_e/u_i parameter to the solar wind data may allow locating the strongest electron-dominated CSs with an ordinary spacecraft resolution of 1−3 s. This study shows that, indeed, electron-dominated CSs observed during a period of quiet solar wind conditions at 1 au impact the surrounding plasma, which may be reflected in sharp changes of u_e/u_i. Electron-dominated CSs are found to be localized in the vicinity of ion-dominated CSs identified via changes in the magnetic field and plasma parameters, displaying the same clustering. We conclude that u_e/u_i may be used as one of the key parameters for statistical studies of CSs in the solar wind and analyzing the role of electrons in them.

X-shaped radio galaxies (XRGs) are those that exhibit two pairs of unaligned radio lobes (main radio lobes and wings). One of the promising models for the peculiar morphology is jet reorientation. To clarify this, we conducted a 5 GHz observation with the European VLBI Network (EVN) of XRG J0725+5835, which resembles the archetypal binary active galactic nuclei (AGNs) 0402+379 in radio morphology, but it is larger in angular size. In our observation, two milliarcsecond-scale radio components with nonthermal radio emission are detected. Each of them coincides with an optical counterpart with similar photometric redshift and (optical and infrared) magnitude, corresponding to dual active nuclei. Furthermore, with the improved Very Large Array (VLA) images, we find a bridge between the two radio cores and a jet bending in the region surrounding the companion galaxy. This further supports the interplay between the main and companion galaxies. In addition, we also report the discovery of an arcsecond-scale jet in the companion. Given the projected separation of ∼100 kpc between the main and companion galaxies, XRG J0725+5835 is likely associated with a dual jetted-AGN system. In both EVN and VLA observations, we find signatures that the jet is changing its direction, which is likely responsible for the X-shaped morphology. For the origin of jet reorientation, several scenarios are discussed.

LaO bands are a characteristic feature in the spectrum of cool S-type stars. La is made primarily by the s-process during the asymptotic giant branch phase of stellar evolution. The B²Σ⁺–X²Σ⁺ and A²Π–X²Σ⁺ band systems can be used to determine the La abundances in cool S stars. The bands of the B²Σ⁺–X²Σ⁺ with and have been rotationally analyzed from an emission spectrum from a carbon furnace. Line strengths are calculated using an ab initio transition dipole function, corrected using experimental lifetimes. We provide a line list for the B²Σ⁺–X²Σ⁺ band system that can be used to determine La abundances.

Giant planets have been discovered at large separations from the central star. Moreover, a striking number of young circumstellar disks have gas and/or dust gaps at large orbital separations, potentially driven by embedded planetary objects. To form massive planets at large orbital separations through core accretion within the disk lifetime, however, an early solid body to seed pebble and gas accretion is desirable. Young protoplanetary disks are likely self-gravitating, and these gravitoturbulent disks may efficiently concentrate solid material at the midplane driven by spiral waves. We run 3D local hydrodynamical simulations of gravitoturbulent disks with Lagrangian dust particles to determine whether particle and gas self-gravity can lead to the formation of dense solid bodies, seeding later planet formation. When self-gravity between dust particles is included, solids of size St = 0.1–1 concentrate within the gravitoturbulent spiral features and collapse under their own self-gravity into dense clumps up to several M_⊕ in mass at wide orbits. Simulations with dust that drift most efficiently, St = 1, form the most massive clouds of particles, while simulations with smaller dust particles, St = 0.1, have clumps with masses an order of magnitude lower. When the effect of dust backreaction onto the gas is included, dust clumps become smaller by a factor of a few but more numerous. The existence of large solid bodies at an early stage of the disk can accelerate the planet formation process, particularly at wide orbital separations, and potentially explain planets distant from the central stars and young protoplanetary disks with substructures.

Recent high-resolution X-ray spectroscopy revealed the possible presence of charge exchange (CX) X-ray emission in supernova remnants (SNRs). Although CX is expected to take place at the outermost edges of SNR shells, no significant measurement has been reported so far due to the lack of nearby SNR samples. Here we present an X-ray study of SNR G296.1−0.5, which has a complicated multiple-shell structure, with the Reflection Grating Spectrometer on board XMM-Newton. We select two shells in different regions and find that in both regions the O vii line shows a high forbidden-to-resonance (f/r) ratio that cannot be reproduced by a simple thermal model. Our spectral analysis suggests a presence of CX and the result is also supported by our new radio observation, where we discover evidence of molecular clouds associated with these shells. Assuming G296.1−0.5 has a spherical shock, we estimate that CX is dominant in a thin layer with a thickness of 0.2%–0.3% of the shock radius. The result is consistent with a previous theoretical expectation and we therefore conclude that CX occurs in G296.1−0.5.

iPTF14hls is a luminous Type II supernova (SN) with a bumpy light curve whose origin remains under debate. It maintains a roughly constant effective temperature and luminosity for about 600 days after discovery, followed by a slow decay. About ∼1000 days after discovery, the light curve transitions to a very steep decline. A spectrum taken during this steep-decline phase shows clear signatures of a shock interaction with a dense circumstellar medium (CSM). Here, we explore the possibility of iPTF14hls as an interaction-powered SN. The light curve of iPTF14hls can be fitted with wind-like CSMs. Analytic modeling indicates that iPTF14hls may have undertaken six episodes of mass loss during the last ∼200 yr. Assuming that the 1954 eruption triggered the last mass-loss episode, the stellar wind velocity is determined to be 40−70 km s⁻¹, depending on different models. Mass-loss rates are in the range 0.4–3.3M_⊙ yr⁻¹. The inferred total mass of the ejecta and CSMs (M_ej + M_CSMs ≃ 245M_⊙) supports the idea that iPTF14hls may be a candidate for a (pulsational) pair-instability SN. Discoveries and observations of similar stellar explosions will help us to understand these peculiar SNe.

Jet precessions are widely involved in astrophysical phenomena from galaxies to X-ray binaries and gamma-ray bursts (GRBs). Polarization presents a unique probe of the magnetic fields in GRB jets. The precession of GRB relativistic jets will change the geometry within the observable emitting region of the jet, which can potentially affect the polarization of the afterglow. In this paper, we take into account jet precession to study the polarization evolution and corresponding light curves in GRB early optical afterglows with ordered and random magnetic field geometries. We find that the jet precession in long-lived engines can significantly reduce the polarization degree (PD) regardless of the magnetic field structure. The strongest PD attenuation is found when the line of sight is aligned with the precession axis. Our results show that jet precession can provide new insight into the low PD measured in the early optical afterglows of GRBs.

We evaluate the cosmological coalescence and detection rates for massive black hole (MBH) binaries targeted by the gravitational wave observatory Laser Interferometer Space Antenna (LISA). Our calculation starts with a population of gravitationally unbound MBH pairs, drawn from the TNG50-3 cosmological simulation, and follows their orbital evolution from kiloparsec scales all the way to coalescence using a semi-analytic model developed in our previous work. We find that for the majority of MBH pairs that coalesce within a Hubble time dynamical friction is the most important mechanism that determines their coalescence rate. Our model predicts an MBH coalescence rate ≲0.45 yr⁻¹ and a LISA detection rate ≲0.34 yr⁻¹. Most LISA detections should originate from 10⁶ to 10^6.8M_⊙ MBHs in gas-rich galaxies at redshifts 1.6 ≤ z ≤ 2.4 and have a characteristic signal-to-noise ratio S/N ∼100. We however find a dramatic reduction in the coalescence and detection rates, as well as the average S/N, if the effects of radiative feedback from accreting MBHs are taken into account. In this case, the MBH coalescence rate is reduced by 78% (to ≲0.1 yr⁻¹), and the LISA detection rate is reduced by 94% (to 0.02 yr⁻¹), whereas the average S/N is ∼10. We emphasize that our model provides a conservative estimate of the LISA detection rates, due to the limited MBH mass range in TNG50-3, consistent with other works in the literature that draw their MBH pairs from cosmological simulations.

Plasma jets and jet fronts are common phenomena in planetary magnetospheres. They are usually associated with many plasma waves and can play a key role in the energy conversion, the excitation of wave emissions, particle acceleration, and the evolution of many astrophysical phenomena, which are major issues in the study of helio-terrestrial space physics. In this paper, we carefully investigated the properties of the whistler-mode wave and large-amplitude electrostatic wave in a plasma jet (bursty bulk flow (BBF)) using the Magnetospheric Multiscale mission data on the Earth's magnetosphere. At the leading part of the BBF, intense whistler-mode waves were observed inside the ion mirror-mode structures, which should be excited by the perpendicular temperature anisotropy of trapping electrons. A small-scale dipolarization front (DF) was then observed at the center of this BBF as a boundary between the leading and trailing parts of the BBF. Behind the DF, both an ion mirror-mode structure and whistler-mode waves disappear, while a large-amplitude electrostatic wave was detected and was associated with the cold ions at the trailing part of the BBF. The electrostatic wave is supposed to be generated by ion beam instability. These results will significantly improve the understanding of the kinetic process associated with the important boundary layer DF within plasma jets. The corresponding wave–particle interaction in space and the plasma environment can be further understood.

In coronal loop modeling, it is commonly assumed that the loops are semicircular with a uniform cross-sectional area. However, observed loops are rarely semicircular, and extrapolations of the magnetic field show that the field strength decreases with height, implying that the cross-sectional area expands with height. We examine these two assumptions directly, to understand how they affect the hydrodynamic and radiative response of short, hot loops to strong, impulsive electron beam heating events. Both the magnitude and rate of area expansion impact the dynamics directly, and an expanding cross section significantly lengthens the time for a loop to cool and drain, increases upflow durations, and suppresses sound waves. The standard T ∼ n² relation for radiative cooling does not hold with expanding loops, which cool with relatively little draining. An increase in the eccentricity of loops, on the other hand, only increases the draining timescale, and is a minor effect in general. Spectral line intensities are also strongly impacted by the variation in the cross-sectional area because they depend on both the volume of the emitting region as well as the density and ionization state. With a larger expansion, the density is reduced, so the lines at all heights are relatively reduced in intensity, and because of the increase of cooling times, the hottest lines remain bright for significantly longer. Area expansion is critical to accurate modeling of the hydrodynamics and radiation, and observations are needed to constrain the magnitude, rate, and location of the expansion—or lack thereof.

The astronomical detection of formamide (NH₂CHO) toward various star-forming regions and in cometary material implies that the simplest amide might have an early origin in dark molecular clouds at low temperatures. Laboratory studies have proven the efficient NH₂CHO formation in interstellar CO:NH₃ ice analogs upon energetic processing. However, it is still under debate, whether the proposed radical–radical recombination reactions forming complex organic molecules remain valid in an abundant H₂O environment. The aim of this work was to investigate the formation of NH₂CHO in H₂O- and CO-rich ices under conditions prevailing in molecular clouds. Therefore, different ice mixtures composed of H₂O:CO:NH₃ (10:5:1), CO:NH₃ (4:1), and CO:NH₃ (0.6:1) were exposed to vacuum ultraviolet photons in an ultra-high vacuum chamber at 10 K. Fourier-transform infrared spectroscopy was utilized to monitor in situ the initial and newly formed species as a function of photon fluence. The infrared spectral identifications are complementarily secured by a temperature-programmed desorption experiment combined with a quadrupole mass spectrometer. The energetic processing of CO:NH₃ ice mixtures mainly leads to the formation of NH₂CHO, along with its chemical derivatives such as isocyanic acid (HNCO) and cyanate ion (OCN⁻). The formation kinetics of NH₂CHO shows an explicit dependency on ice ratios and compositions; the highest yield is found in H₂O-rich ice. The astronomical relevance of the resulting reaction network is discussed.

Recent observations provided evidence that the solar chromosphere of sunspot regions is pervaded by Alfvénic waves—transverse magnetohydrodynamic (MHD) waves (Alfvén waves or kink waves). In order to systematically investigate the physical characteristics of Alfvénic waves over a wide range of periods, we analyzed the time series of line-of-sight velocity maps constructed from the Hα spectral data of a small sunspot region taken by the Fast Imaging Solar Spectrograph of the Goode Solar Telescope at Big Bear. We identified each Alfvénic wave packet by examining the cross-correlation of band-filtered velocity between two points that are located a little apart presumably on the same magnetic field line. As result, we detected a total of 279 wave packets in the superpenumbral region around the sunspot and obtained their statistics of period, velocity amplitude, and propagation speed. An important finding of ours is that the detected Alfvénic waves are clearly separated into two groups: 3-minute period (<7 minutes) waves and 10-minute period (>7 minutes) waves. We propose two tales on the origin of Alfvénic waves in the chromosphere; the 3-minute Alfvénic waves are excited by the upward-propagating slow waves in the chromosphere through the slow-to-Alfvénic mode conversion, and the 10-minute Alfvénic waves represent the chromospheric manifestation of the kink waves driven by convective motions in the photosphere.

A set of 464 minutes of high-resolution high-cadence observations were acquired for a region near the Sun’s disk center using the Interferometric BI-dimensional Spectrometer installed at the Dunn Solar Telescope. Ten sets of Dopplergrams are derived from the bisector of the spectral line corresponding approximately to different atmospheric heights, and two sets of Dopplergrams are derived using an MDI-like algorithm and center-of-gravity method. These data are then filtered to keep only acoustic modes, and phase shifts are calculated between Doppler velocities of different atmospheric heights as a function of acoustic frequency. The analysis of the frequency- and height-dependent phase shifts shows that, for evanescent acoustic waves, oscillations in the higher atmosphere lead those in the lower atmosphere by an order of 1 s when their frequencies are below about 3.0 mHz, and lags behind by about 1 s when their frequencies are above 3.0 mHz. Nonnegligible phase shifts are also found in areas with systematic upward or downward flows. All these frequency-dependent phase shifts cannot be explained by vertical flows or convective blueshifts, but are likely due to complicated hydrodynamics and radiative transfer in the nonadiabatic atmosphere in and above the photosphere. These phase shifts in the evanescent waves pose great challenges to the interpretation of some local helioseismic measurements that involve data acquired at different atmospheric heights or in regions with systematic vertical flows. More quantitative characterization of these phase shifts is needed so that they can either be removed during measuring processes or be accounted for in helioseismic inversions.

The Seyfert 1 galaxy NGC 7469 possesses a prominent nuclear starburst ring and a luminous active galactic nucleus (AGN). Evidence of an outflow in the innermost nuclear region has been found in previous works. We detect the ionized gas outflow on a larger scale in the galaxy using the archival Very Large Telescope/MUSE and Chandra observations. The optical emission lines are modeled using two Gaussian components, and a nonparametric approach is applied to measure the kinematics of [O iii] and Hα emitting gas. Line ratio diagnostics and spatially resolved maps are derived to examine the origin of the outflow. The kiloparsec-scale kinematics of [O iii] are dominated by a blueshifted component whereas the velocity map of Hα shows a rotational disk with a complex nonrotational substructure. The starburst wind around the circumnuclear ring is confirmed, and we find evidence of an AGN-driven outflow extending to a radial distance of ∼ 2 kpc from the nucleus, with a morphology consistent with a nearly face-on ionization cone. The previously reported circumnuclear outflow resembles part of the bright base. We derive mass and energy outflow rates for both the starburst wind and the AGN-driven outflow. The estimated kinetic coupling efficiency of the kiloparsec-scale AGN outflow is , lower than the threshold predicted by the “two-stage” theoretical model for effective feedback. Our results reinforce the importance of spatially resolved study to disentangle feedback where AGNs and starbursts coexist, which may be common during the cosmic noon of black hole and galaxy growth.

We perform a full nuclear-network numerical calculation of the r-process nuclei in binary neutron-star mergers (NSMs), with the aim of estimating gamma-ray emissions from the remnants of Galactic NSMs up to 10⁶ yr old. The nucleosynthesis calculation of 4070 nuclei is adopted to provide the elemental composition ratios of nuclei with an electron fraction Y_e between 0.10 and 0.45. The decay processes of 3237 unstable nuclei are simulated to extract the gamma-ray spectra. As a result, the NSMs have different spectral colors in the gamma-ray band from various other astronomical objects at less than 10⁵ yr old. In addition, we propose a new line diagnostic method for Y_e that uses the line ratios of either ^137mBa/⁸⁵K or ²⁴³Am/^60mCo, which become larger than unity for young and old r-process sites, respectively, with a low-Y_e environment. From an estimation of the distance limit for gamma-ray observations as a function of age, the high sensitivity in the sub-megaelectronvolt band, at approximately 10⁻⁹ photons s⁻¹ cm⁻² or 10⁻¹⁵ erg s⁻¹ cm⁻², is required to cover all the NSM remnants in our Galaxy, if we assume that the population of NSMs by Wu et al. A gamma-ray survey with sensitivities of 10⁻⁸–10⁻⁷ photons s⁻¹ cm⁻² or 10⁻¹⁴–10⁻¹³ erg s⁻¹ cm⁻² in the 70–4000 keV band is expected to find emissions from at least one NSM remnant under the assumption of an NSM rate of 30 Myr⁻¹. The feasibility of gamma-ray missions observing Galactic NSMs is also studied.

We study the evolution of rapid neutron-capture process (r-process) isotopes in the galaxy. We analyze relative contributions from core-collapse supernovae (CCSNe), neutron star mergers, and collapsars under a range of astrophysical conditions and nuclear input data. Here we show that, although the r-process in each of these sites can lead to a similar (universal) elemental distribution, the detailed isotopic abundances can differ from one site to another. These differences may allow for the identification of which sources contributed to the early evolution of r-process material in the galaxy. Our simulations suggest that the early evolution was dominated by CCSNe and collapsar r-process nucleosynthesis. This conclusion may be testable if the next generation of observatories can deduce isotopic r-process abundances.

We model the response of spherical, nonrotating Milky Way (MW) dark matter and stellar halos to the Large Magellanic Cloud using the matrix method of linear response theory. Our computations reproduce the main features of the dark halo response from simulations. We show that these features can be well separated by a harmonic decomposition: the large-scale over/underdensity in the halo (associated with its reflex motion) corresponds to the ℓ = 1 terms, and the local overdensity to the ℓ ≥ 2 multipoles. Moreover, the dark halo response is largely dominated by the first-order forcing term, with little influence from self-gravity. This makes it difficult to constrain the underlying velocity distribution of the dark halo using the observed response of the stellar halo, but it allows us to investigate the response of stellar halo models with various velocity anisotropies: a tangential (respectively radial) halo produces a shallower (respectively stronger) response. We also show that only the local wake is responsible for these variations, the reflex motion being solely dependent on the MW potential. Therefore, we identify the structure (orientation and winding) of the in-plane quadrupolar (m = 2) response as a potentially good probe of the stellar halo anisotropy. Finally, our method allows us to tentatively relate the wake strength and shape to resonant effects: the strong radial response could be associated with the inner Lindblad resonance, and the weak tangential one with corotation.

We combine stellar surface rotation periods determined from NASA’s Kepler mission with spectroscopic temperatures to demonstrate the existence of pileups at the long-period and short-period edges of the temperature–period distribution for main-sequence stars with temperatures exceeding ∼5500 K. The long-period pileup is well described by a curve of constant Rossby number, with a critical value of Ro_crit ≲ Ro_⊙. The long-period pileup was predicted by van Saders et al. as a consequence of weakened magnetic braking, in which wind-driven angular momentum losses cease once stars reach a critical Rossby number. Stars in the long-period pileup are found to have a wide range of ages (∼2–6 Gyr), meaning that, along the pileup, rotation period is strongly predictive of a star’s surface temperature but weakly predictive of its age. The short-period pileup, which is also well described by a curve of constant Rossby number, is not a prediction of the weakened magnetic braking hypothesis but may instead be related to a phase of slowed surface spin-down due to core-envelope coupling. The same mechanism was proposed by Curtis et al. to explain the overlapping rotation sequences of low-mass members of differently aged open clusters. The relative dearth of stars with intermediate rotation periods between the short- and long-period pileups is also well described by a curve of constant Rossby number, which aligns with the period gap initially discovered by McQuillan et al. in M-type stars. These observations provide further support for the hypothesis that the period gap is due to stellar astrophysics, rather than a nonuniform star formation history in the Kepler field.

The Trappist-1 planets provide a unique opportunity to test the current understanding of rocky planet evolution. The James Webb Space Telescope is expected to characterize the atmospheres of these planets, potentially detecting CO₂, CO, H₂O, CH₄, or abiotic O₂ from water photodissociation and subsequent hydrogen escape. Here, we apply a coupled atmosphere–interior evolution model to the Trappist-1 planets to anticipate their modern atmospheres. This model, which has previously been validated for Earth and Venus, connects magma ocean crystallization to temperate geochemical cycling. Mantle convection, magmatic outgassing, atmospheric escape, crustal oxidation, a radiative-convective climate model, and deep volatile cycling are explicitly coupled to anticipate bulk atmospheres and planetary redox evolution over 8 Gyr. By adopting a Monte Carlo approach that samples a broad range of initial conditions and unknown parameters, we make some tentative predictions about current Trappist-1 atmospheres. We find that anoxic atmospheres are probable, but not guaranteed, for the outer planets; oxygen produced via hydrogen loss during the pre-main sequence is typically consumed by crustal sinks. In contrast, oxygen accumulation on the inner planets occurs in around half of all models runs. Complete atmospheric erosion is possible but not assured for the inner planets (occurs in 20%–50% of model runs), whereas the outer planets retain significant surface volatiles in virtually all model simulations. For all planets that retain substantial atmospheres, CO₂-dominated or CO₂–O₂ atmospheres are expected; water vapor is unlikely to be a detectable atmospheric constituent in most cases. There are necessarily many caveats to these predictions, but the ways in which they misalign with upcoming observations will highlight gaps in terrestrial planet knowledge.

X-ray binaries (XRBs) consist of a compact object that accretes material from an orbiting secondary star. The most secure method we have for determining if the compact object is a black hole is to determine its mass: This is limited to bright objects and requires substantial time-intensive spectroscopic monitoring. With new X-ray sources being discovered with different X-ray observatories, developing efficient, robust means to classify compact objects becomes increasingly important. We compare three machine-learning classification methods (Bayesian Gaussian Processes (BGPs), K-Nearest Neighbors (KNN), Support Vector Machines) for determining whether the compact objects are neutron stars or black holes (BHs) in XRB systems. Each machine-learning method uses spatial patterns that exist between systems of the same type in 3D color–color–intensity diagrams. We used lightcurves extracted using 6 yr of data with MAXI/GSC for 44 representative sources. We find that all three methods are highly accurate in distinguishing pulsing from nonpulsing neutron stars (NPNS) with 95% of NPNS and 100% of pulsars accurately predicted. All three methods have high accuracy in distinguishing BHs from pulsars (92%) but continue to confuse BHs with a subclass of NPNS, called bursters, with KNN doing the best at only 50% accuracy for predicting BHs. The precision of all three methods is high, providing equivalent results over 5–10 independent runs. In future work, we will suggest a fourth dimension be incorporated to mitigate the confusion of BHs with bursters. This work paves the way toward more robust methods to efficiently distinguish BHs, NPNS, and pulsars.