Sazuna/UAT_keywords huggingface dataset:
Living with a Red Dwarf: X-Ray, UV, and Ca II Activity-Age Relationships of M Dwarfs. The vast majority of stars in the nearby stellar neighborhood are M dwarfs. Their low masses and luminosities result in slow rates of nuclear evolution and minimal changes to the stars' observable properties, even along astronomical timescales. However, they possess relatively powerful magnetic dynamos and resulting X-ray to UV (X-UV) activity, compared to their bolometric luminosities. This magnetic activity does undergo an observable decline over time, potentially making it a key age determinant for M dwarfs. Observing this activity is important for studying the outer atmospheres of these stars, but also for comparing the behaviors of different spectral type subsets of M dwarfs; e.g., those with partially versus fully convective interiors. Beyond stellar astrophysics, understanding the X-UV activity of M dwarfs over time is a key component when studying the atmospheres and habitability of any hosted exoplanets. Earth-sized exoplanets, in particular, are more commonly found orbiting M dwarfs than any other stellar type, and thermal escape (driven by the M dwarf X-UV activity) is believed to be the dominant atmospheric loss mechanism for these planets. Utilizing recently calibrated M dwarf age-rotation relationships, also constructed as part of the Living with a Red Dwarf program, we have analyzed the evolution of M dwarf activity over time, in terms of coronal (X-ray), chromospheric (Lyα, and Ca II), and overall X-UV (5-1700 Å) emissions. The activity-age relationships presented here will be useful for studying exoplanet habitability and atmospheric loss, and also for studying the different dynamo and outer atmospheric heating mechanisms at work in M dwarfs.

Keywords: X-ray astronomy, M dwarf stars, Stellar ages, Late-type dwarf stars, Stellar chromospheres, Ultraviolet astronomy, Low mass stars, Stellar rotation, Stellar coronae, Stellar atmospheres, Stellar evolution
The Effects of Thomson Scattering and Chemical Mixing on Early-time Light Curves of Double-peaked Type IIb Supernovae. Previous numerical simulations of double-peaked Type IIb supernova (SN IIb) light curves have demonstrated that the radius and mass of the hydrogen-rich envelope of the progenitor star can significantly influence the brightness and timescale of the early-time light curve around the first peak. In this study, we investigate how Thomson scattering and chemical mixing in the SN ejecta affect the optical light curves during the early stages of the SNe IIb using radiation hydrodynamics simulations. By comparing the results from two different numerical codes (i.e., STELLA and SNEC), we find that the optical brightness of the first peak can be reduced by more than a factor of 3 as a result of the effect of Thomson scattering that causes the thermalization depth to be located below the Rosseland mean photosphere, compared to the corresponding case where this effect is ignored. We also observe a short-lived plateau-like feature lasting for a few days in the early-time optical light curves of our models, in contrast to typical observed SNe IIb that show a quasi-linear decrease in optical magnitudes after the first peak. A significant degree of chemical mixing between the hydrogen-rich envelope and the helium core in SN ejecta is required to reconcile this discrepancy between the model prediction and observation. Meanwhile, to properly reproduce the first peak, a significant mixing of 56Ni into the hydrogen-rich outermost layers should be restricted. Our findings indicate that inferring the SN IIb progenitor structure from a simplified approach that ignores these two factors may introduce substantial uncertainty.

Keywords: Type II supernovae, Core-collapse supernovae
Low-frequency Internal Gravity Waves Are Pseudo-incompressible. Starting from the fully compressible fluid equations in a plane-parallel atmosphere, we demonstrate that linear internal gravity waves are naturally pseudo-incompressible in the limit that the wave frequency ω is much less than that of surface gravity waves, i.e., $\omega \ll \sqrt{{{gk}}_{h}}$ , where g is the gravitational acceleration and k  h  is the horizontal wavenumber. We accomplish this by performing a formal expansion of the wave functions and the local dispersion relation in terms of a dimensionless frequency $\varepsilon =\omega /\sqrt{{{gk}}_{h}}$ . Further, we show that, in this same low-frequency limit, several forms of the anelastic approximation, including the Lantz-Braginsky-Roberts formulation, poorly reproduce the correct behavior of internal gravity waves. The pseudo-incompressible approximation is achieved by assuming that Eulerian fluctuations of the pressure are small in the continuity equation-whereas, in the anelastic approximation, Eulerian density fluctuations are ignored. In an adiabatic stratification, such as occurs in a convection zone, the two approximations become identical. However, in a stable stratification, the differences between the two approximations are stark and only the pseudo-incompressible approximation remains valid.

Keywords: Hydrodynamical simulations, Internal waves, Stellar convective zones, Stellar interiors, Solar convective zone, Stellar oscillations, Planetary interior, Astrophysical fluid dynamics
Binary Vision: The Mass Distribution of Merging Binary Black Holes via Iterative Density Estimation. Binary black hole (BBH) systems detected via gravitational-wave emission are a recently opened astrophysical frontier with many unknowns and uncertainties. Accurate reconstruction of the binary distribution with as few assumptions as possible is desirable for inference of formation channels and environments. Most population analyses have, though, assumed a power law in binary mass ratio q, and/or assumed a universal q distribution regardless of primary mass. Methods based on kernel density estimation allow us to dispense with such assumptions and directly estimate the joint binary mass distribution. We deploy a self-consistent iterative method to estimate this full BBH mass distribution, finding local maxima in primary mass consistent with previous investigations and a secondary mass distribution with a partly independent structure, inconsistent both with a power law and with a constant function of q. We find a weaker preference for near-equal-mass binaries than in most previous investigations; instead, the secondary mass has its own "spectral lines" at slightly lower values than the primary, and we observe an anticorrelation between primary and secondary masses around the ~10 M ⊙ peak.

Keywords: Gravitational waves
The Observed O VI Is Just the Tip of the Iceberg: Estimating the Hidden Material in Circumgalactic and Intergalactic Clouds. This paper proposes a new method for estimating the total quantity of material in moving circumgalactic and intergalactic clouds from O VI measurements. We simulate high-velocity clouds (HVCs) with the FLASH hydrodynamic code and track the ionization and recombination of all ionization levels of oxygen as a function of time. We calculate the O VI/oxygen ratio (f O VI ) in our dynamic nonequilibrium ionization clouds, finding that it differs significantly from that in static gas. We find that O VI exists in cool, medium, and hot gas in the clouds. As such, it traces all of the hydrogen rather than merely the ionized hydrogen. The total quantity of hydrogen along a typical observed line of sight through a cloud can be estimated from the observed O VI column density, metallicity, and our f O VI . We provide the simulations' f O VI  values, a prescription for finding f O VI  for observed dynamic clouds, and a methodology for calculating the total hydrogen column density from f O VI  and an observed O VI column density. As examples, we use our f O VI  values to estimate the total hydrogen column densities along various observed sight lines through two HVCs, Complex C and the Magellanic Stream, finding that these clouds contain more material than previous lower limits. We also extend this analysis to low-redshift intergalactic O VI clouds, finding that they contain several times more baryonic material than previously thought and therefore may account for a significant fraction of the Universe's baryons.

Keywords: Hydrodynamical simulations, Intergalactic clouds, High-velocity clouds, Interstellar clouds, Magellanic Stream, Hot ionized medium
Measuring Mass and Radius of the Maximum-mass Nonrotating Neutron Star. The mass (M TOV) and radius (R TOV) of the maximum-mass nonrotating neutron star (NS) play a crucial role in constraining the elusive equation of state of cold dense matter and in predicting the fate of remnants from binary neutron star (BNS) mergers. In this study, we introduce a novel method to deduce these parameters by examining the mergers of second-generation (2G) black holes (BHs) with NSs. These 2G BHs are assumed to originate from supramassive neutron stars (SMNSs) formed in BNS mergers. Since the properties of the remnant BHs arising from the collapse of SMNSs follow a universal relation governed by M TOV and R TOV, we anticipate that by analyzing a series (~100 detections) of mass and spin measurements of the 2G BHs using the third-generation ground-based gravitational-wave detectors, M TOV and R TOV can be determined with a precision of ~0.01M ⊙ and ~0.6 km, respectively.

Keywords: Gravitational wave sources, Compact objects
Observation of Interchange Reconnection on Mars. Without a global dipole magnetic field, Mars has magnetic anomalies, i.e., crustal fields, in the southern hemisphere and interesting flexible magnetic fields in the magnetotail. The magnetic field topology is complex and flexible in the Martian magnetotail, especially over regions of strong crustal fields. However, the answer to how the magnetic field topology within crustal field regions transitions is elusive. Here we report the first case of interchange reconnection between open and closed crustal fields in the near-Mars magnetotail, using Mars Atmosphere and Volatile Evolution (MAVEN) observations. While MAVEN crossed from a region of closed crustal field to one of open crustal field, several characteristics of reconnection, such as the Hall magnetic field and plasma outflow, were observed. And plasmas are exchanged in the reconnection region. Our observations demonstrate that interchange reconnection can occur between open and closed crustal fields in the Martian near-magnetotail. Interchange reconnection occurring on the nightside changes the magnetic field topology within the crustal field regions and contributes to the escape of heavy ions.

Keywords: Planetary magnetospheres, Mars, Magnetic fields, Plasma physics
An Explanation for the Overrepresentation of Tidal Disruption Events in Post-starburst Galaxies. Tidal disruption events (TDEs) provide a valuable probe for studying the dynamics of stars in the nuclear environments of galaxies. Recent observations show that TDEs are strongly overrepresented in post-starburst or "green valley" galaxies, although the underlying physical mechanism remains unclear. Considering the possible interaction between stars and active galactic nucleus (AGN) disks, the TDE rates can be greatly changed compared to those in quiescent galactic nuclei. In this work, we revisit TDE rates by incorporating an evolving AGN disk within the framework of "loss cone" theory. We numerically evolve the Fokker-Planck equations by considering star-disk interactions, in situ star formation in the unstable region of the outer AGN disk, and evolution of the accretion process of supermassive black holes. We find that the TDE rates are enhanced by about 2 orders of magnitude shortly after the AGN transitions into an inactive stage. During this phase, the accumulated stars rapidly scatter into the loss cone due to the disappearance of the inner standard thin disk. Our results provide an explanation for the overrepresentation of TDEs in post-starburst galaxies.

Keywords: Tidal disruption, Active galactic nuclei, Green valley galaxies
A New Insight into Electron Acceleration Properties from Theoretical Modeling of Double-peaked Radio Light Curves in Core-collapse Supernovae. It is recognized that some core-collapse supernovae (SNe) show a double-peaked radio light curve within a few years since the explosion. A shell of circumstellar medium (CSM) detached from the SN progenitor has been considered to play a viable role in characterizing such a rebrightening of radio emission. Here, we propose another mechanism that can give rise to the double-peaked radio light curve in core-collapse SNe. The key ingredient in the present work is to expand the model for the evolution of the synchrotron spectral energy distribution (SED) to a generic form, including fast and slow cooling regimes, as guided by the widely accepted modeling scheme of gamma-ray burst afterglows. We show that even without introducing an additional CSM shell, the radio light curve would show a double-peaked morphology when the system becomes optically thin to synchrotron self-absorption at the observational frequency during the fast cooling regime. We can observe this double-peaked feature if the transition from the fast cooling to slow cooling regime occurs during the typical observational timescale of SNe. This situation is realized when the minimum Lorentz factor of injected electrons is initially large enough for the nonthermal electrons' SED to be discrete from the thermal distribution. We propose SN 2007bg as a special case of double-peaked radio SNe that can be possibly explained by the presented scenario. Our model can serve as a potential diagnostic for electron acceleration properties in SNe.

Keywords: Particle astrophysics, Non-thermal radiation sources, Core-collapse supernovae, Radio transient sources
Halo Mass-observable Proxy Scaling Relations and Their Dependencies on Galaxy and Group Properties. Based on the DECaLS shear catalog, we study the scaling relations between halo mass (M h) and various proxies for Sloan Digital Sky Survey central galaxies, including stellar mass (M *), stellar velocity dispersion (σ *), abundance-matching halo mass (M AM), and satellite velocity dispersion (σ s), and their dependencies on galaxy and group properties. In general, these proxies all have strong positive correlations with M h, consistent with previous studies. We find that the M h-M * and M h-σ * relations depend strongly on group richness (N sat), while the M h-M AM and M h-σ s relations are independent of it. Moreover, the dependence on the star formation rate (SFR) is rather weak in the M h-σ * and M h-σ s relations, but very prominent in the other two. σ s is thus the best proxy among them, and its scaling relation is in good agreement with hydrodynamical simulations. However, estimating σ s accurately for individual groups/clusters is challenging because of interlopers and the requirement for sufficient satellites. We construct new proxies by combining M *, σ *, and M AM, and find that the proxy with 30% contribution from M AM and 70% from σ * can minimize the dependence on N sat and the SFR. We obtain the M h-supermassive black hole (SMBH) mass relation via the SMBH scaling relation and find indications for rapid and linear growth phases for the SMBH. We also find that correlations among M h, M *, and σ * change with M *, indicating that different processes drive the growth of galaxies and SMBHs at different stages.

Keywords: Weak gravitational lensing, Galaxy dark matter halos, Galaxies
Search for Supernova Progenitor Stars with ZTF and LSST. The direct detection of core-collapse supernova (SN) progenitor stars is a powerful way of probing the last stages of stellar evolution. However, detections in archival Hubble Space Telescope images are limited to about one detection per year. Here, we explore whether we can increase the detection rate by using data from ground-based wide-field surveys. Due to crowding and atmospheric blurring, progenitor stars can typically not be identified in preexplosion images alone. Instead, we combine many pre-SN and late-time images to search for the disappearance of the progenitor star. As a proof of concept, we implement our search of ZTF data. For a few hundred images, we achieve limiting magnitudes of ~23 mag in the g and r bands. However, no progenitor stars or long-lived outbursts are detected for 29 SNe within z ≤ 0.01, and the ZTF limits are typically several magnitudes less constraining than detected progenitors in the literature. Next, we estimate progenitor detection rates for the Legacy Survey of Space and Time (LSST) with the Vera C. Rubin telescope by simulating a population of nearby SNe. The background from bright host galaxies reduces the nominal LSST sensitivity by, on average, 0.4 mag. Over the 10 yr survey, we expect the detection of ~50 red supergiant progenitors and several yellow and blue supergiants. The progenitors of Type Ib and Ic SNe will be detectable if they are brighter than -4.7 or -4.0 mag in the LSST i band, respectively. In addition, we expect the detection of hundreds of pre-SN outbursts depending on their brightness and duration.

Keywords: Massive stars, Red supergiant stars, Sky surveys, Core-collapse supernovae
LATIS: The Stellar Mass-Metallicity Relation of Star-forming Galaxies at z   2.5. We present the stellar mass-stellar metallicity relation for 3491 star-forming galaxies at 2 ≲ z ≲ 3 using rest-frame far-ultraviolet spectra from the Lyα Tomography IMACS Survey (LATIS). We fit stellar population synthesis models from the Binary Population And Spectral Synthesis code (v2.2.1) to medium-resolution (R ~ 1000) and high signal-to-noise (&gt;30 per 100 km s-1 over the wavelength range 1221-1800 Å) composite spectra of galaxies in bins of stellar mass to determine their stellar metallicity, primarily tracing Fe/H. We find a strong correlation between stellar mass and stellar metallicity, with stellar metallicity monotonically increasing with stellar mass at low masses and flattening at high masses (M * ≳ 1010.3 M ⊙). Additionally, we compare our stellar metallicity measurements with the gas-phase oxygen abundance of galaxies at similar redshift and estimate the average [α/Fe] ~ 0.6. Such high α-enhancement indicates that high-redshift galaxies have not yet undergone significant iron enrichment through Type Ia supernovae. Moreover, we utilize an analytic chemical evolution model to constrain the mass loading parameter of galactic winds as a function of stellar mass. We find that as the stellar mass increases, the mass loading parameter decreases. The parameter then flattens or reaches a turning point at around M * ~ 1010.5 M ⊙. Our findings may signal the onset of black-hole-driven outflows at z ~ 2.5 for galaxies with M * ≳ 1010.5 M ⊙.

Keywords: High-redshift galaxies, Metallicity, Galaxy evolution
High-energy Neutrinos from Gamma-Ray-faint Accretion-powered Hypernebulae. Hypernebulae are inflated by accretion-powered winds accompanying hyper-Eddington mass transfer from an evolved post-main-sequence star onto a black hole or neutron star companion. The ions accelerated at the termination shock-where the collimated fast disk winds and/or jet collide with the slower, wide-angled wind-fed shell-can generate high-energy neutrinos via hadronic proton-proton reactions, and photohadronic (p γ) interactions with the disk thermal and Comptonized nonthermal background photons. It has been suggested that some fast radio bursts (FRBs) may be powered by such short-lived jetted hyper-accreting engines. Although neutrino emission associated with the millisecond duration bursts themselves is challenging to detect, the persistent radio counterparts of some FRB sources-if associated with hypernebulae-could contribute to the high-energy neutrino diffuse background flux. If the hypernebula birth rate follows that of stellar-merger transients and common envelope events, we find that their volume-integrated neutrino emission-depending on the population-averaged mass-transfer rates-could explain up to ~25% of the high-energy diffuse neutrino flux observed by the IceCube Observatory and the Baikal Gigaton Volume Detector Telescope. The time-averaged neutrino spectrum from hypernebula-depending on the population parameters-can also reproduce the observed diffuse neutrino spectrum. The neutrino emission could in some cases furthermore extend to &gt;100 PeV, detectable by future ultra-high-energy neutrino observatories. The large optical depth through the nebula to Breit-Wheeler (γ γ) interaction attenuates the escape of GeV-PeV gamma rays coproduced with the neutrinos, rendering these gamma-ray-faint neutrino sources, consistent with the Fermi observations of the isotropic gamma-ray background.

Keywords: X-ray binary stars, Jets, Binary stars, High energy astrophysics, Compact nebulae, Neutrino astronomy, Plasma astrophysics, High mass x-ray binary stars, Ultraluminous x-ray sources, Nebulae, Shocks, Particle astrophysics
A Multiwavelength Investigation of PSR J2229+6114 and its Pulsar Wind Nebula in the Radio, X-Ray, and Gamma-Ray Bands. G106.3+2.7, commonly considered to be a composite supernova remnant (SNR), is characterized by a boomerang-shaped pulsar wind nebula (PWN) and two distinct ("head" and "tail") regions in the radio band. A discovery of very-high-energy gamma-ray emission (E  γ  &gt; 100 GeV) followed by the recent detection of ultrahigh-energy gamma-ray emission (E  γ  &gt; 100 TeV) from the tail region suggests that G106.3+2.7 is a PeVatron candidate. We present a comprehensive multiwavelength study of the Boomerang PWN (100″ around PSR J2229+6114) using archival radio and Chandra data obtained two decades ago, a new NuSTAR X-ray observation from 2020, and upper limits on gamma-ray fluxes obtained by Fermi-LAT and VERITAS observatories. The NuSTAR observation allowed us to detect a 51.67 ms spin period from the pulsar PSR J2229+6114 and the PWN emission characterized by a power-law model with Γ = 1.52 ± 0.06 up to 20 keV. Contrary to the previous radio study by Kothes et al., we prefer a much lower PWN B-field (B ~ 3 μG) and larger distance (d ~ 8 kpc) based on (1) the nonvarying X-ray flux over the last two decades, (2) the energy-dependent X-ray size of the PWN resulting from synchrotron burn-off, and (3) the multiwavelength spectral energy distribution (SED) data. Our SED model suggests that the PWN is currently re-expanding after being compressed by the SNR reverse shock ~1000 yr ago. In this case, the head region should be formed by GeV-TeV electrons injected earlier by the pulsar propagating into the low-density environment.

Keywords: X-ray astronomy, Gamma-ray astronomy, Pulsar wind nebulae
Multiscale Dynamical Scenario of High-mass Star Formation in an IRDC Filament G34. There is growing evidence that high-mass star formation (HMSF) is a multiscale, dynamical process in molecular clouds, where filaments transport gas material between larger and smaller scales. We analyze here multiscale gas dynamics in an HMSF filamentary cloud, G034.43+00.24 (G34), using APEX observations of the C18O (2-1), HCO+/H13CO+ (3-2), and HCN/H13CN (3-2) lines. We find large-scale, filament-aligned velocity gradients from C18O emission, which drive filamentary gas inflows onto dense clumps in the middle ridge of G34. The nature of these inflows is gravity driven. We also find clump-scale gas infall in the middle ridge of the MM2, MM4, and MM5 clumps from other lines. Their gas infall rates could depend on large-scale filamentary gas inflows since the infall/inflow rates on these two scales are comparable. We confirm that the multiscale, dynamical HMSF scenario is at work in G34. It could be driven by gravity up to the filament scale, beyond which turbulence originating from several sources, including gravity, could be in effect in G34.

Keywords: Molecular gas, Infrared dark clouds, Star forming regions, Molecular clouds, Young stellar objects