Sazuna/UAT_keywords huggingface dataset:
The Role of High-mass Stellar Binaries in the Formation of High-mass Black Holes in Dense Star Clusters. Recent detections of gravitational waves from mergers of binary black holes (BBHs) with premerger source-frame individual masses in the so-called upper mass gap, expected due to (pulsational) pair instability supernovae ((P)PISNe), have created immense interest in the astrophysical production of high-mass black holes (BHs). Previous studies show that high-mass BHs may be produced via repeated BBH mergers inside dense star clusters. Alternatively, inside dense star clusters, stars with unusually low core-to-envelope mass ratios can form via mergers of high-mass stars, which then can avoid (P)PISN, but produce high-mass BHs via mass fallback. We simulate detailed star-by-star multiphysics models of dense star clusters using the Monte Carlo cluster evolution code CMC, to investigate the role of primordial binary fraction among high-mass stars (≥15 M⊙) on the formation of high-mass BHs. We vary the high-mass stellar binary fraction ( fb,15' ) while keeping all other initial properties, including the population of high-mass stars, unchanged. We find that the number of high-mass BHs, as well as the mass of the most massive BH formed via stellar core collapse are proportional to  fb,15' . In contrast, there is no correlation between  fb,15'  and the number of high-mass BHs formed via BH–BH mergers. Since the total production of high-mass BHs is dominated by BH–BH mergers in old clusters, the overall number of high-mass BHs produced over the typical lifetime of globular clusters is insensitive to  fb,15' . We study the differences in the demographics of BH–BH mergers and their implications for LIGO–Virgo–Kagra detections as a function of  fb,15' .

Keywords: Intermediate-mass black holes, Binary stars, Monte Carlo methods, Massive stars, Stellar dynamics, Computational methods, Gravitational waves, Star clusters
Stellar Ages: A Code to Infer Properties of Stellar Populations. We present a novel statistical algorithm, Stellar Ages, which currently infers the age, metallicity, and extinction posterior distributions of stellar populations from their magnitudes. While this paper focuses on these parameters, the framework is readily adaptable to include additional properties, such as rotation, in future work. Historical age-dating techniques either model individual stars or populations of stars, often sacrificing population context or precision for individual estimates. Stellar Ages does both, combining the strengths of these approaches to provide precise individual ages for stars while leveraging population-level constraints. We verify the algorithm's capabilities by determining the age of synthetic stellar populations and actual stellar populations surrounding a nearby supernova, SN 2004dj. In addition to inferring an age, we infer a progenitor mass consistent with direct observations of the precursor star. The median age inferred from the brightest nearby stars is  log10 (Age yr−1) =  7.19−0.13+0.10 , and its corresponding progenitor mass is  13.95−1.96+3.33  M⊙.

Keywords: Stellar populations, Massive stars, Supernovae, Core-collapse supernovae
Stellar Tidal Disruptions by Newborn Neutron Stars or Black Holes: A Mechanism for Hydrogen-poor (Super)luminous Supernovae and Fast Blue Optical Transients. Hydrogen-poor supernovae (SNe) of Type Ibc are explosions of massive stars that lost their hydrogen envelopes, typically due to interactions with a binary companion. We consider the case where the natal kick imparted to the neutron star (NS) or black hole (BH) remnant brings the compact object to a collision with a main-sequence companion, eventually leading to full tidal disruption of the companion. Subsequently, super-Eddington accretion onto the NS/BH launches a powerful, fast wind which collides with the SN ejecta and efficiently converts the kinetic energy of the wind into radiation. The radiation is reprocessed by the surrounding ejecta into a luminous (∼1044 erg s‑1 at peak), days to months-long transient with optical peaks from ‑19 to ‑21 mag, comparable to (super)luminous Type Ibc SNe and fast blue optical transients (FBOTs) such as AT2018cow. From a Monte Carlo analysis, we estimate the fraction of tidal disruptions following SNe in binaries to be ∼0.1%–1%, roughly compatible with the event rates of these luminous SNe. At the broad-brush level, our model reproduces the multiwavelength and spectral observations of FBOTs, and has the potential to explain peculiar features seen in some (super)luminous SNe that are difficult to reproduce by the conventional magnetar spin-down mechanism, such as late-time hydrogen lines, bumpy light curves, and prepeak excess.

Keywords: Theoretical models, Binary stars, Transient sources, Core-collapse supernovae
From Larger-scale Cold-gas Angular Momentum Environments to Galaxy Star Formation Activity. We study the influence of the ambient large-scale cold-gas vorticity on the specific star formation rate (sSFR) of central galaxies with stellar masses of  10.0&lt;logM∗/M⊙&lt;11.5  at z = 0, using the TNG100 simulation. The cold-gas vorticity defined and calculated for gas with Tgas &lt; 2 × 104 K and on scales of ∼1 Mpc can well describe the angular motion of the ambient cold gas. We find crucial evidence for connections between the cold-gas vorticity and level of star formation activity, such that at any given halo mass (particularly below 1013 M⊙), galaxies living in higher cold-gas vorticity environments are generally less star-forming, regardless of their large-scale environment types (filament or knot), or star formation states (star-forming or quenched). In particular, at a fixed halo mass scale of 1012–1013 M⊙, the median sSFR of galaxies living in environments with the top 30% cold-gas vorticity is ∼0.5 dex below that of galaxies living in environments with the bottom 30% cold-gas vorticity. At any fixed halo mass scale, cold-gas vorticities around filament galaxies are generally higher than those around knot galaxies, consistent with the fact that filament galaxies have lower sSFRs than knot galaxies. This large-scale cold-gas vorticity is highly connected to the orbital angular momentum of neighboring galaxies up to a distance of ∼500 kpc, indicating their common origin and a possible angular momentum inheritance/modulation from the latter to the former. The negative modulation by the environmental vorticity on galaxy star formation is only significantly observed for the cold gas, indicating the unique role of cold-gas angular momentum.

Keywords: Hydrodynamical simulations, Galaxy formation, Galaxy evolution, Large-scale structure of the universe
Dust Growth in ALMA Rings. II. Dusty Rossby Wave Instability. Annular substructures serve as ideal venues for planetesimal formation. In this series, we investigate the linear stage of dust growth within rings. The first paper in this series examines the global streaming instability, while this study focuses on the dusty Rossby wave instability (DRWI). To this end, we perform a linear analysis of the two-fluid equations on a background pressure bump, representing annular substructures. The spectral code DEDALUS is used to solve the linear eigenvalue problem. We identify two distinct DRWI modes: Type I, which originates from dust-modified gas RWI, and Type II, which results from dust-gas coupling. Type I and Type II modes never coexist for a given azimuthal wavenumber ky, but transition between each other as ky varies. Type I modes are driven by the advection of background vorticity, and Type II modes possess two waves: Rossby waves, driven by advection, and thin waves, driven by dust-gas drag. Finally, we assess the relevance of DRWI in Atacama Large Millimeter/submillimeter Array (ALMA) rings using DSHARP sources. Our findings suggest that Type I modes could explain the absence of azimuthal asymmetries in many ALMA disks, whereas Type II modes are entirely absent in all eight observed rings, implying that unresolved narrow rings or alternative mechanisms may play a role in dust growth within annular substructures.

Keywords: Astrophysical dust processes, Planet formation, Protoplanetary disks, Hydrodynamics
Deep Ultraviolet, Emission-line Imaging of the Makani Galactic Wind. The O VI 1032, 1038 Å line is a key probe of cooling gas in the circumgalactic medium (CGM) of galaxies but has been observed to date primarily in absorption along single sight lines. We present deep Hubble Space Telescope (HST) Solar Blind Channel of the Advanced Camera for Surveys observations of the compact, massive starburst Makani. Makani hosts a 100 kpc, [O II]-emitting galactic wind driven by two episodes of star formation over 400 Myr. We detect O VI and Lyα emission across the [O II] nebula with similar morphology and extent, out to r ≍ 50 kpc. Using differential narrowband imaging, we separate Lyα and O VI and show that the O VI emission is comparable in brightness to [O II], with LO VI = 4 × 1042 erg s−1. The similar hourglass morphology and size of [O II] and O VI implicate radiative cooling at T = 105.5 K in a hot─cold interface. This may occur as the T &gt; 107 K CGM—or the hot fluid driving the wind—exchanges mass with the T ≍ 104 K clouds entrained in (or formed by) the wind. The optical/UV line ratios may be consistent with shock ionization, although uncertain attenuation and Lyα radiative transfer complicate the interpretation. The detection of O VI in Makani lies at the bleeding edge of the UV imaging capabilities of HST and provides a benchmark for future emission-line imaging of the CGM with a wide-area UV telescope.

Keywords: Starburst galaxies, Galaxy winds, Circumgalactic medium
The Galactic Population of Magnetars: A Simulation-based Inference Study. Population synthesis modeling of the observed dynamical and physical properties of a population is a highly effective method for constraining the underlying birth parameters and evolutionary tracks. In this work, we apply a population synthesis model to the canonical magnetar population to gain insight into the parent population. We utilize simulation-based inference to reproduce the observed magnetar population with a model that takes into account the secular evolution of the force-free magnetosphere and magnetic field decay simultaneously and self-consistently. Our observational constraints are such that no magnetar is detected through their persistent emission when convolving the simulated populations with the XMM-Newton EPIC-pn Galactic plane observations, and that all of the ∼30 known magnetars are discovered through their bursting activity in the last ∼50 yr. Under these constraints, we find, within 95% credible intervals, the birth rate of magnetars to be  1.8‑0.6+2.6  kyr‑1, leading to having  10.7‑4.4+18.8 % of neutron stars born as magnetars. We also find a mean magnetic field at birth (μb is in T)  logμb=10.2‑0.2+0.1 , a magnetic field decay slope  αd=1.9‑1.3+0.9 , and timescale  τd=17.9‑14.5+24.1  kyr, in broad agreement with previous estimates. We conclude this study by exploring detection prospects: an all-sky survey with XMM-Newton would potentially allow around seven periodic detections of magnetars to be obtained, with approximately 150 magnetars exceeding XMM-Newton's flux threshold, and the upcoming AXIS experiment should allow these detections to be doubled.

Keywords: Magnetars, X-ray sources, X-ray bursts
Application of a Low-dissipation HLLD Approximate Riemann Solver to Solar Wind Simulations. We investigate the steady-state solar wind in spherical coordinates using a low-dissipation Harten–Lax–van Leer-Discontinuities Riemann solver, in which the magnetic field is decomposed into an initial potential field B0 and a time-dependent part B1. A constrained transport method is employed to effectively preserve the divergence-free condition, with the relative divergence errors maintained at truncation level throughout the simulation. The solar wind plasma and magnetic field equations are solved using a one-step MUSCL-type time integration scheme, combined with spacetime reconstruction at cell interfaces and edges. Prior to the solar wind simulation, the accuracy and robustness of the numerical method are verified through benchmark tests, including the smooth Alfvén wave problem, the Mach 800 dense MHD jet, and the MHD blast wave in spherical polar coordinates. The results confirm that the scheme achieves second-order accuracy and remains stable under challenging physical conditions. The validated scheme is then applied to simulate the structured solar wind during Carrington Rotation 2236, using Helioseismic and Magnetic Imager 720 s cadence line-of-sight magnetograms as input. The simulation successfully reproduces key large-scale solar wind features, such as polar and extended coronal holes, open and closed magnetic field regions, helmet streamers, pseudo-streamers, the heliospheric current sheet, and the spatial distribution of fast and slow solar wind streams. Comparisons with remote sensing observations and in situ measurements demonstrate reasonable agreement. However, discrepancies remain in the temporal variations of plasma parameters and the detailed structure of coronal holes, suggesting areas for further model refinement.

Keywords: Magnetohydrodynamics, Solar wind, Solar corona
Comparison of Bar Formation Mechanisms. II. Does a Tidally Induced Bar Grow Faster than an Internally Developed Bar?. Bar structures can form internally due to the instability of their host galaxies or externally due to perturbations from other galaxies. We systematically quantify the growth timescales (τbar) of bars formed through these two mechanisms with a series of controlled N-body simulations. In galaxies susceptible to bar instability, tidally induced bars display τbar values comparable to those of internally developed bars within the same disk. Tidal perturbations promote (delay) bar formation by advancing (postponing) its onset, but the growth rate of the bar structure remains largely unchanged. In these interaction scenarios, the bar formation is still driven primarily by the galaxy's internal nature, which remains unaffected by tidal perturbations. As the external perturbation wave reaches the galaxy's center, it evokes a "seed bar" that is then swing amplified. In this scenario, the onset of bar formation is advanced. Conversely, bar formation may be delayed if the external perturbation wave is out of phase with the preexisting spontaneously developed "seed bar," which causes destructive interference and limits bar growth. In the hot disk model that resists bar formation in isolation, the τbar of the tidally forced bar correlates with the strength of the perturbation. The bar growth in this model deviates from an exponential profile and is better described by a linear function. The varied τbar and the preference for linear growth contrast with bars formed in galaxies inherently susceptible to bar instability. These tidally forced bars may not adhere to the swing amplification mechanism that predicts exponential bar growth.

Keywords: Galaxy structure, Galaxy dynamics, Galaxy kinematics, Barred spiral galaxies
Global Simulations of Gravitational Instability in Protostellar Disks with Full Radiation Transport. I. Stochastic Fragmentation with Optical-depth-dependent Rate and Universal Fragment Mass. Fragmentation in a gravitationally unstable accretion disk can be an important pathway for forming stellar/planetary companions. To characterize quantitatively the condition for and outcome of fragmentation under realistic thermodynamics, we perform global 3D simulations of gravitationally unstable disks at various cooling rates and cooling types, including the first global simulations of gravitational instability that employ full radiation transport. We find that fragmentation is a stochastic process, with the fragment generation rate per disk area pfrag showing an exponential dependence on the parameter β ≡ ΩKtcool, where ΩK is the Keplerian rotation frequency, and tcool is the average cooling timescale. Compared to a prescribed constant β, radiative cooling in the optically thin/thick regime makes pfrag decrease slower/faster in β; the critical β corresponding to ∼1 fragment per orbit is ≈3, 5, and 2 for constant β, optically thin, and optically thick cooling, respectively. The distribution function of the initial fragment mass is remarkably insensitive to disk thermodynamics. Regardless of cooling rate and optical depth, the typical initial fragment mass is mfrag ≈ 40Mtoth3, with Mtot being the total (star+disk) mass and h = H/R being the disk aspect ratio. Applying this result to typical Class 0/I protostellar disks, we find mfrag ∼ 20MJ, suggesting that fragmentation more likely forms brown dwarfs. Given the finite width of the mfrag distribution, forming massive planets is also possible.

Keywords: Planet formation, Gravitational instability, Protoplanetary disks, Radiative transfer
Global Simulations of Gravitational Instability in Protostellar Disks with Full Radiation Transport. II. Locality of Gravitoturbulence, Clumpy Spirals, and Implications for Observable Substructure. Spiral perturbations in a gravitationally unstable accretion disk regulate disk evolution through angular momentum transport and heating and provide an observational signature of gravitational instability (GI). We use global 3D simulations to systematically characterize and understand these spiral perturbations. The spiral perturbations and the resulting transport are overall insensitive to the cooling type, with the exception that radiative cooling, especially in the optically thick regime, reduces the amplitude of temperature perturbations. Spiral perturbations are localized around corotation, allowing transport to be approximated by a local α viscosity to zeroth order in aspect ratio (H/R), but only after averaging over multiple orbits in time and/or multiple scale heights in space. Meanwhile, large-amplitude perturbations from strong gravitoturbulence can cause  O(α1/2)  deviation in the cooling rate of the disk. We develop empirical prescriptions for the angular momentum transport, heating, and cooling in a gravitoturbulent disk that capture the deviation from a viscous, unperturbed disk to first order in H/R and α1/2. The spiral perturbations in saturated gravitoturbulence are clumpy, with dense clumps forming through the nonlinear coupling between multiple modes at different m. Observationally, the clumpy gravitoturbulence produced by saturated GI can be mistaken with observational noise or embedded companions, especially under finite resolution. Meanwhile, grand-design spirals with m-fold symmetry may be uncommon among disks in saturated gravitoturbulence, and we speculate that they may instead be a signature of recently triggered or decaying GI.

Keywords: Planet formation, Gravitational instability, Protoplanetary disks, Radiative transfer
Methods to Test the Source of the Extreme Gas Motions in WS 35. We present theoretical arguments toward the plausibility of a stellar wind to explain the 16,000 km s‑1 line broadening in the optical spectra of WS 35, the central star in the Pa 30 nebula. The wind model is discussed in the context of super-Eddington flows. We argue that WS 35 potentially occupies a new regime of wind driving theory as the first metal-only wind. This framework provides a promising avenue for explaining the high-speed flow. We further describe how future radio observations can provide an independent test of the spherical wind scenario. A magnetically channeled wind would likely produce a relatively flat and bright radio spectral energy distribution. By contrast, a spherical wind should result in a thermal radio spectrum with a canonical continuum slope of ν0.6, and a brightness level consistent with the currently predicted mass-loss rate.

Keywords: Stellar magnetic fields, Stellar winds, Circumstellar disks, Stellar remnants, Radio astronomy
Missing Titanium in the Asymmetric Supernova Remnant W 49B. The progenitor of the W 49B supernova remnant is still under debate. One of the candidates is a jet-driven core-collapse supernova. In such a highly asymmetric explosion, a strong α-rich freeze-out is expected in local high-entropy regions, which should enrich elements synthesized by the capture of α-particles such as 44Ti and 48Cr (decaying to 44Ca and 48Ti, respectively). In the present work, in order to infer the progenitor of the W 49B remnant, we constrain the amount of stable Ti (48Ti) synthesized, using Suzaku observations. We found no firm evidence for the Ti line and set the upper limit of MTi/MFe &lt; 9.9 × 10‑4 (99% limit using Xspec/AtomDB) and MTi/MFe &lt; 5.8 × 10‑4 (99% limit using SPEX). Our limits can exclude almost all core-collapse supernova models, suggesting that a Type Ia supernova from a near-Chandrasekhar-mass white dwarf is the most favorable candidate for the origin of W 49B. Future observations with X-ray microcalorimeter missions, such as XRISM, will give us a stronger constraint on the progenitor.

Keywords: Supernova remnants, Explosive nucleosynthesis, X-ray astronomy, Nucleosynthesis
A Successful Sheared-arcade Eruption Triggered by a Failed Erupted Small Filament. In this work, we analyze a successful eruption, accompanied by an X5.4-class flare in active region 11429. The eruptive structure is an elongated hot structure, with two curved brightenings below it. Additionally, we find that snail-shell-shaped flare loops are formed at the end of the flare, with a filament channel beneath the loops that implies a magnetic flux rope structure. The flare ribbons indicate a highly complex eruption process. During the eruption, using Global Oscillation Network Group data, we find a small filament that exists before and after the eruption. We reproduce the eruption using a full thermodynamic magnetohydrodynamic simulation, with the purpose to illustrate the mechanisms of the eruption. The small magnetic flux rope continuously rises due to arcade–arcade to rope–flare loop reconnection below, compressing the sheared magnetic arcades above. Slipping reconnection between the upper sheared magnetic arcades leads to the formation of new sheared magnetic arcades, resulting in a successful eruption. Simultaneously, the newly formed snail-shell-shaped flare loops constrain the elevation of the original magnetic flux rope below, implying that the original magnetic flux rope is not the eruptive structure of this successful eruption. Instead, the sheared magnetic arcades produced by the upper slipping reconnection above the original flux rope is the eruptive structure involved.

Keywords: Solar flares, Solar magnetic reconnection, Magnetic fields, Magnetohydrodynamical simulations
Mass of Cepheid V350 Sgr Incorporating Interferometry and the Companion Mass. The system V350 Sgr has a classical Cepheid for the primary. Interferometry is presented for the system, and the full orbit is determined. The mass of the companion has been determined from an International Ultraviolet Explorer spectrum and comparison with the mass─temperature relation from detached eclipsing binaries. Combined with the mass of the companion (2.6 ± 0.2 M⊙), the mass of the Cepheid is determined to be 4.7 ± 0.8 M⊙. For systems with less complete information, Cepheid masses can be determined from a single-lined spectroscopic orbit, Gaia proper motion anomalies, and the mass of the companion from the ultraviolet. Uncertainties resulting from different approaches to mass determination are discussed and are expected to be reduced after the Gaia DR4 release. Temperatures for Morgan─Keenan standard stars from the ultraviolet are also provided.

Keywords: Cepheid variable stars, Stellar masses