Sazuna/UAT_keywords huggingface dataset:
Simulating Short Gamma-Ray Burst Jets in Realistic Late Binary Neutron Star Merger Environments. The electromagnetic emission and the afterglow observations of the binary neutron star merger event GW170817A confirmed the association of the merger with a short gamma-ray burst (GRB) harboring a narrow (5°–10°) and powerful (1049–1050 erg) jet. Using the 1 s long neutrino-radiation general relativistic MHD simulation of coalescing neutron stars of K. Kiuchi et al., and following the semi-analytical estimates of M. Pais et al., we inject a narrow, powerful, unmagnetized jet into the post-merger phase. We explore different opening angles, luminosities, central engine durations, and times after the merger. We explore early (0.1 s following the merger) and late (1 s) jet launches; the latter is consistent with the time delay of ≈1.74 s observed between GW170817 and GRB 170817A. We demonstrate that the semi-analytical estimates correctly predict the jets' breakout and collimation conditions. When comparing our synthetic afterglow light curves to the observed radio data of GW170807, we find a good agreement for a 3 × 1049 erg jet launched late with an opening angle in the range ≃5°–7°.

Keywords: Neutron stars, Hydrodynamical simulations, Gamma-ray bursts, Relativistic jets
DESI Massive Poststarburst Galaxies at z ∼ 1.2 Have Compact Structures and Dense Cores. Poststarburst galaxies (PSBs) are young quiescent galaxies that have recently experienced a rapid decrease in star formation, allowing us to probe the fast-quenching period of galaxy evolution. In this work, we obtained Hubble Space Telescope (HST)/WFC3 F110W imaging to measure the sizes of 171 massive ( log(M*/M⊙)∼11)  spectroscopically identified PSBs at 1 &lt; z 1.3 selected from the DESI Survey Validation luminous red galaxy sample. This statistical sample constitutes an order of magnitude increase from the ∼20 PSBs with space-based imaging and deep spectroscopy. We perform structural fitting of the target galaxies with pysersic and compare them to quiescent and star-forming galaxies in the 3D-HST survey. We find that these PSBs are more compact than the general population of quiescent galaxies, lying systematically ∼0.1 dex below the established size–mass relation. However, their central surface mass densities are similar to those of their quiescent counterparts ( log(Σ1kpc/(M⊙kpc‑2))∼10.1 ). These findings are easily reconciled by later ex situ growth via minor mergers or a slight progenitor bias. These PSBs are round in projection (b/a median ∼ 0.8), suggesting that they are primarily spheroids, not disks, in 3D. We find no correlation between the time since quenching and light-weighted PSB sizes or central densities. This disfavors apparent structural growth due to the fading of centralized starbursts in this galaxy population. Instead, we posit that the fast quenching of massive galaxies at this epoch occurs preferentially in galaxies with preexisting compact structures.

Keywords: Galaxy quenching, Galaxies, Galaxy evolution, Post-starburst galaxies
How the Galaxy–Halo Connection Depends on Large-scale Environment. We investigate the connection between galaxies, dark matter halos, and their large-scale environments at z = 0 with Illustris TNG300 hydrodynamic simulation data. We predict stellar masses from subhalo properties to test two types of machine learning (ML) models: explainable boosting machines (EBMs) with simple galaxy environment features and  E(3) -invariant graph neural networks (GNNs). The best-performing EBM models leverage spherically averaged overdensity features on 3 Mpc scales. Interpretations via SHapley Additive exPlanations also suggest that in the context of the TNG300 galaxy–halo connection, simple spherical overdensity on ∼3 Mpc scales is more important than cosmic web distance features measured using the DisPerSE algorithm. Meanwhile, a GNN with connectivity defined by a fixed linking length, L, outperforms the EBM models by a significant margin. As we increase the linking length scale, GNNs learn important environmental contributions up to the largest scales we probe (L = 10 Mpc). We conclude that 3 Mpc distance scales are most critical for describing the TNG galaxy–halo connection using the spherical overdensity parameterization, but that information on larger scales, which is not captured by simple environmental parameters or cosmic web features, can further augment these models. Our study highlights the benefits of using interpretable ML algorithms to explain models of astrophysical phenomena, and the power of using GNNs to flexibly learn complex relationships directly from data while imposing constraints from physical symmetries.

Keywords: Galaxy dark matter halos, Hydrodynamical simulations, Large-scale structure of the universe, Astrostatistics techniques, Galaxy evolution
Self-consistent Disk-reflection Analysis of the Black Hole Candidate X-Ray Binary MAXI J1813‑095 with NICER, Swift, Chandra, and NuSTAR. We present our analysis of MAXI J1813‑095 during its hard state "stalled" outburst in 2018. This self-consistent analysis has been carried out using the Neutron Star Interior Composition Explorer, Swift, Chandra, and NuSTAR throughout seven observations of MAXI J1813‑095. We find a relativistic iron line at ∼6.5 keV from the inner region of the accretion disk. Our results are consistent with a slightly truncated disk or nontruncated disk for an inner radius of ∼2R g and minimum spin of &gt;0.7 with the best value of ∼0.9, assuming R in reaches the innermost stable circular orbit at L x ∼ 1% L Edd. We analyzed MAXI J1813‑095 over its outburst, employing a spectral model that self-consistently couples the seed disk photons to the Comptonization and reflection components, also inclusive of reflection Comptonization. The unique aspect of this work is a reflection fraction of order unity, which is significantly higher than previous studies of this source and is a consequence of applying the self-consistent disk-Comptonization-reflection spectral model. Other key parameters, such as inclination and inner radius, are found to be consistent with other works.

Keywords: Black holes, Compact objects
ÆSOPUS 2.1: Low-temperature Opacities Extended to High Pressure. We address the critical need for accurate Rosseland mean gas opacities in high-pressure environments, spanning temperatures from 100 K to 32,000 K. Current opacity tables from Wichita State University and ÆSOPUS 2.0 are limited to  log(R)≤1 , where  R=ρT6‑3  in units of  gcm‑3(106K)‑3 . This is insufficient for modeling very low-mass stars, brown dwarfs, and planets with atmospheres exhibiting higher densities and pressures ( log(R)&gt;1 ). Leveraging extensive databases such as ExoMol, ExoMolOP, MoLLIST, and HITEMP, we focus on expanding the ÆSOPUS opacity calculations to cover a broad range of pressure and density conditions ( ‑8≤log(R)≤+6 ). We incorporate the thermal Doppler mechanism and microturbulence velocity. Pressure-broadening effects on molecular transitions, leading to Lorentzian or Voigt profiles, are explored in the context of atmospheric profiles for exoplanets, brown dwarfs, and low-mass stars. We also delve into the impact of electron degeneracy and nonideal effects, such as ionization potential depression under high-density conditions, emphasizing its notable influence on Rosseland mean opacities at temperatures exceeding 10,000 K. As a result, this study expands the ÆSOPUS public web interface for customized gas chemical mixtures, promoting flexibility in opacity calculations based on specific research needs. Additionally, precomputed opacity tables, inclusive of condensates, are provided. We present a preliminary application to evolutionary models for very low-mass stars.

Keywords: Brown dwarfs, Exoplanets, Stellar atmospheric opacity, Astrochemistry, Low mass stars, Collisional broadening
High-redshift, Small-scale Tests of Ultralight Axion Dark Matter Using Hubble and Webb Galaxy UV Luminosities. We calculate the abundance of UV-bright galaxies in the presence of ultralight axion (ULA) dark matter (DM), finding that axions suppress their formation with a non-trivial dependence on redshift and luminosity. We set limits on axion DM using UV luminosity function (UVLF) data, excluding a single axion as all the DM for m ax &lt; 10‑21.6 eV and limiting axions with  ‑26≤log(max/eV)≤‑23  to be less than 22% of the DM (both at 95% credibility). These limits use UVLF measurements from 24,000 sources from the Hubble Space Telescope (HST) at redshifts 4 ≤ z ≤ 10. We marginalize over a parametric model connecting halo mass and UV luminosity. Our results bridge a window in axion mass and fraction previously unconstrained by cosmological data, between large-scale cosmic microwave background and galaxy clustering and the small-scale Lyα forest. These high-z measurements provide a powerful consistency check of low-z tests of axion DM, including the recent hint for a sub-dominant ULA DM fraction in Lyα forest data. We also consider a sample of 25 spectroscopically confirmed high-z galaxies from the James Webb Space Telescope (JWST), finding these data to be consistent with HST. Combining HST and JWST UVLF data does not improve our constraints beyond HST alone, but future JWST measurements have the potential to improve these results. We also find an excess of low-mass halos (&lt;109 M ⊙) at z &lt; 3, which could be probed by subgalactic structure probes (e.g., stellar streams, satellite galaxies, and strong lensing).

Keywords: Cosmology, Galaxy dark matter halos, Hubble Space Telescope, James Webb Space Telescope, Markov chain Monte Carlo, Galaxy luminosities, Dark matter
KBSS-InCLOSE. I. Design and First Results from the Inner Circumgalactic Medium of QSO Line-of-sight Emitting Galaxies at z ∼ 2─3. We present the design and first results of the inner circumgalactic medium (CGM) of QSO line-of-sight emitting galaxies at z ∼ 2─3, Keck Baryonic Structure Survey (KBSS)-InCLOSE. The survey will connect galaxy properties (e.g., stellar mass M *, interstellar medium, hereafter ISM, metallicity) with the physical conditions of the inner CGM (e.g., kinematics, metallicity) to directly observe the galaxy-scale baryon cycle. We obtain deep Keck/KCWI optical IFU pointings of KBSS QSOs to discover new star-forming galaxies at small projected distances b ≲ 12″ (98 kpc,  z̄=2.3 ), then obtain follow-up Keck/MOSFIRE near-IR spectra to confirm their redshifts. We leverage KBSS images and Keck/High Resolution Echelle Spectrometer QSO spectra to model stellar populations and inner CGM absorption. In this paper, we analyze two QSO fields and discover more than 15 new galaxies with KCWI, then use MOSFIRE for two galaxies Q2343-G1 (z = 2.43; G1) and Q2233-N1 (z = 3.15; N1), which are both associated with damped Lyα absorbers. We find that G1 has typical M *, UV/optical emission properties. N1 has lower M * with very strong nebular emission. We jointly analyze neutral phase CGM and ionized ISM in N/O (for the first time at this z), dust extinction, and high-ionization CGM finding that G1's CGM is metal poor and less evolved than its ISM, while N1's CGM and ISM abundances are comparable; their CGM shows ∼1 dex less dust extinction than the ISM; and G1's CGM has direct evidence of hot, metal-rich galactic outflow ejecta. These findings support that metals and dust are driven into the CGM from outflows, but may also be, e.g., stripped ISM gas or satellite enrichment. The full KBSS-InCLOSE sample will explore these scenarios. * Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c)3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Keywords: Abundance ratios, Galaxy chemical evolution, Intergalactic medium, Quasar absorption line spectroscopy, Damped Lyman-alpha systems, Interstellar medium, Circumgalactic medium, Extragalactic astronomy
VLT/MUSE Detection of Accretion/Ejection Associated with the Close Stellar Companion in the HT Lup System. The accretion/ejection processes in T Tauri stars are fundamental to their physical evolution, while also impacting the properties and evolution of the circumstellar material at a time when planet formation takes place. To date, the characterization of ongoing accretion processes in stellar pairs at 5─50 au scales has been challenging as high-angular resolution spectrographs are required to extract the spectral features of each component. We present the analysis of spectroscopic observations of the tight (160 mas, 25 au) T Tauri system HT Lup A/B, obtained with MUSE at the Very Large Telescope in 2021 March and July. We focus on constraining the accretion/ejection processes and variability of the secondary component HT Lup B by searching for accretion tracers by applying high-resolution spectral differential imaging techniques. We retrieve strong (signal-to-noise ratio &gt; 5) Hα, Hβ, and [O I]λ6300 emission in both epochs. The Hα and Hβ line fluxes showcase high variability, with variations up to 200%─300% between epochs. The fluxes are consistent with accretion rates of 3× 10−9 M ⊙ yr−1 and 8 × 10−10 M ⊙ yr−1 for the first and second epochs, respectively. We attribute the increased accretion activity during the first night to a "burst-like" event, followed by a relaxation period more representative of the common accretion activity of the system. The [O I]λ6300 line profiles remain relatively similar between epochs and suggest ejection rates on the order of 10−9−10−10 M ⊙ yr−1, compatible with moderate disk wind emission. Our results also indicate that the accretion processes of HT Lup B are compatible with Classical T Tauri stars, unlike previous classifications.

Keywords: High contrast techniques, Accretion, Binary stars, Close binary stars, T Tauri stars, Young stellar objects, Direct imaging, Stellar accretion, High contrast spectroscopy
Predicting Photospheric Ultraviolet Emission from Stellar Evolutionary Models. Stellar ultraviolet (UV) emission serves as a crucial indicator for estimating magnetic activity and evaluating the habitability of exoplanets orbiting stars. In this paper, we present a straightforward method to derive stellar photospheric UV emission for F to M main-sequence stars. By using PARSEC models, we establish relations between near-UV (NUV) and far-UV (FUV) magnitudes from the Galaxy Evolution Explorer, NUV magnitudes from the China Space Station Telescope, and stellar effective temperatures and Gaia blue photometer–red photometer colors for different metallicities. Together with the observed sample, we find that for NUV emission, the photospheric contribution to the observed flux is less than 20% for M stars, around 10%–70% for K stars, and in a range from 30% to 85% for G and F stars. For FUV emission, the photospheric contribution is less than 10‑6 for M stars, below 10‑4 for K stars, around 10‑4–10% for G stars, and between 6% and 50% for F stars. Our work enables the simple and effective determination of stellar excess UV emission and the exploration of magnetic activity.

Keywords: Stellar chromospheres, Stellar photospheres, Ultraviolet photometry, Stellar activity
Examining the Relationship between the Persistent Emission and the Accretion Rate during a Type I X-Ray Burst. The accretion flow onto a neutron star will be impacted by irradiation from a type I X-ray burst. The burst radiation exerts Poynting–Robertson (PR) drag on the accretion disk, leading to an enhanced mass accretion rate. Observations of X-ray bursts often find evidence that the normalization of the disk-generated persistent emission (commonly denoted by the factor f  a ) increases during a burst, and changes in f  a  have been used to infer the evolution of the mass accretion rate due to PR drag. Here, we examine this proposed relationship between f  a  and mass accretion rate enhancement using time-resolved data from simulations of accretion disks impacted by type I X-ray bursts. We consider bursts from both spinning and nonspinning neutron stars and track both the change in accretion rate due to PR drag and the disk emission spectra during the burst. Regardless of the neutron star spin, we find that f  a  strongly correlates with the disk temperature and only weakly follows the mass accretion rate (the Pearson correlation coefficients are ≤0.63 in the latter case). Additionally, heating causes the disk to emit at higher energies, reducing its contribution to a soft excess. We conclude that f  a  cannot accurately capture the mass accretion rate enhancement and is rather a tracer of the disk temperature.

Keywords: Accretion, Neutron stars, Low-mass x-ray binary stars, X-ray bursts
Persistent Behavior in Energetic Neutral Atom Time Series from IBEX. We investigate the long-term persistence of the time series of energetic neutral atom (ENA) fluxes recorded by the Interstellar Boundary Explorer (IBEX). ENAs provide global information about the outer heliosphere and its interactions with the very local interstellar medium. To avoid the IBEX Ribbon, here, we focus our analysis solely on the polar regions N60°–N90° and S60°–S90°. Each year, IBEX takes two measurements of every pixel in the sky. We make use of the whole set of 14 yr of IBEX data and adhere to the correct time order for the construction of the flux time series. We examine in detail both the trend and the fluctuations of these time series. Using modern methods of time series analysis and persistence characterization, we show that the time series (i) trend is influenced by the solar cycle, (ii) persistence can be established independently of the presence of this trend, and (iii) statistical properties of the fluctuations differs between north and south, pointing to the existence of anisotropy and thus a north–south asymmetry.

Keywords: Solar cycle, Heliosphere, Astrostatistics techniques, Solar wind, Interstellar magnetic fields, Pickup ions, Interstellar medium, Solar activity, Heliosheath, Interdisciplinary astronomy, Time series analysis
Asteroseismology of One of the Most Rapidly Rotating DBV Stars: EPIC 248705247. We present a comprehensive analysis of oscillations of the helium-rich white dwarf DBV star EPIC 248705247 (SDSS J102106.69+082724.8). We extract the light curves from 79.7 days of K2 Campaign 14 data and identify 21 independent frequencies, including three complete and three incomplete dipole modes, with an average frequency splitting of 20.37 ± 0.40 μHz. Our analyses reveal a rotation period of EPIC 248705247 of approximately 6.82 ± 0.07 hr, making it one of the most rapidly rotating DBV stars currently known. We utilize the White Dwarf Evolution Code (WDEC) to compute models to look for the seismic best-fitted model, yielding the following stellar parameters: M/M ⊙ = 0.650 ± 0.003, T eff = 23,660 ± 68 K,  log(Menv/M*)=‑2.01±0.01  and  log(MHe/M*)=‑4.90±0.05 . We also explore the phenomenon of mode trapping, as well as the potential influence of a weak magnetic field. We find that this star is located near the red edge of the theoretical instability strip of DBVs. Hence, our asteroseismological analysis of EPIC 248705247 provides the properties and behaviors of a rapidly rotating DBV.

Keywords: White dwarf stars, DB stars
Origin and Full Characterization of the Secondary (Assembly) Halo Bias. The clustering of dark matter halos depends not only on their mass, the so-called primary bias, but also on their internal properties, the so-called secondary bias. While the former effect is well understood within the Press–Schechter and excursion set models of structure formation, the latter is not. In those models, protohalos are fully characterized by their height and scale, which determine the halo mass and collapse time, so there is no room for any other halo property. This is why the secondary bias was believed not to be innate but due to the distinct merger rate of halos lying in different backgrounds, and dubbed assembly bias. However, it has now been determined that mergers leave no imprint in the inner halo properties. In fact, the innate origin of the secondary bias cannot be discarded because, in the more realistic peak model of structure formation, halo seeds are characterized by one additional property: the peak curvature. Here, we use the confluent system of peak trajectory formalism to show that peaks lying in different backgrounds have different mean curvatures, which in turn cause them to evolve into halos with different typical inner properties. The dependence we find of the properties on halo background (or halo clustering) reproduces the results of simulations.

Keywords: Cosmology, Galaxy dark matter halos, Hierarchical cosmology, Dark matter
Large-scale Cosmic-ray Anisotropies with 19 yr of Data from the Pierre Auger Observatory. Results are presented for the measurement of large-scale anisotropies in the arrival directions of ultra–high-energy cosmic rays detected at the Pierre Auger Observatory during 19 yr of operation, prior to AugerPrime, the upgrade of the observatory. The 3D dipole amplitude and direction are reconstructed above 4 EeV in four energy bins. Besides the established dipolar anisotropy in R.A. above 8 EeV, the Fourier amplitude of the 8–16 EeV energy bin is now also above the 5σ discovery level. No time variation of the dipole moment above 8 EeV is found, setting an upper limit to the rate of change of such variations of 0.3% yr‑1 at the 95% confidence level. Additionally, the results for the angular power spectrum are shown, demonstrating no other statistically significant multipoles. The results for the equatorial dipole component down to 0.03 EeV are presented, using for the first time a data set obtained with a trigger that has been optimized for lower energies. Finally, model predictions are discussed and compared with observations, based on two source emission scenarios obtained in the combined fit of spectrum and composition above 0.6 EeV.

Keywords: Ultra-high-energy cosmic radiation
Mind the Kinematics Simulation of Planet–Disk Interactions: Time Evolution and Numerical Resolution. Planet–disk interactions can produce kinematic signatures in protoplanetary disks. While recent observations have detected non-Keplerian gas motions in disks, their origins are still being debated. To explore this, we conduct 3D hydrodynamic simulations using the code FARGO3D to study nonaxisymmetric kinematic perturbations at two scale heights induced by Jovian planets in protoplanetary disks, followed by examinations of detectable signals in synthetic CO emission line observations at millimeter wavelengths. We advocate for using residual velocity or channel maps, generated by subtracting an azimuthally averaged background of the disk, to identify planet-induced kinematic perturbations. We investigate the effects of two basic simulation parameters, simulation duration and numerical resolution, on the simulation results. Our findings suggest that a short simulation (e.g., 100 orbits) is insufficient to establish a steady velocity pattern given our chosen viscosity (α = 10‑3) and displays plenty of fluctuations on an orbital timescale. Such transient features could be detected in observations. By contrast, a long simulation (e.g., 1000 orbits) is required to reach steady state in kinematic structures. At 1000 orbits, the strongest detectable velocity structures are found in the spiral wakes close to the planet. Through numerical convergence tests, we find hydrodynamics results converge in spiral regions at a resolution of 14 cells per disk scale height or higher. Meanwhile, synthetic observations produced from hydrodynamic simulations at different resolutions are indistinguishable with 0.″1 angular resolution and 10 hr of integration time on Atacama Large Millimeter/submillimeter Array.

Keywords: Radiative transfer, Planetary-disk interactions, Protoplanetary disks, Hydrodynamics