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

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

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

Keywords: Magnetohydrodynamics, Quiet solar corona, Solar extreme ultraviolet emission
The MASSIVE Survey. XX. A Triaxial Stellar Dynamical Measurement of the Supermassive Black Hole Mass and Intrinsic Galaxy Shape of Giant Radio Galaxy NGC 315. We present a new dynamical measurement of the supermassive black hole mass and intrinsic shape of the stellar halo of the massive radio galaxy NGC 315 as part of the MASSIVE survey. High signal-to-noise ratio spectra from integral-field spectrographs at the Gemini and McDonald Observatories provide stellar kinematic measurements in 304 spatial bins from the central  ∼0.″3  out to 30″. Using ∼2300 kinematic constraints, we perform triaxial stellar orbit modeling with the TriOS code and search over ∼15,000 galaxy models with a Bayesian scheme to simultaneously measure six mass and intrinsic shape parameters. NGC 315 is triaxial and highly prolate, with middle-to-long and short-to-long axis ratios of p = 0.854 and q = 0.833, and a triaxiality parameter of T = 0.89. The black hole mass inferred from our stellar kinematics is  MBH=3.0±0.3×109M⊙ , which is higher than  MBH=(1.96−0.13+0.30)×109M⊙  inferred from CO kinematics (scaled to our distance). When the seven galaxies with MBH measurements from both stellar and CO kinematics are compared, we find an intrinsic scatter of 0.28 dex in MBH from the two tracers and do not detect statistically significant biases between the two methods in the current data. The implied black hole shadow size (≍4.7 μas) and the relatively high millimeter flux of NGC 315 makes this galaxy a prime candidate for future horizon-size imaging studies.

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

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

Keywords: Galactic winds, Starburst galaxies
Modeling Star Formation Histories of Changing-look AGN Host Galaxies with Prospector. Changing-look active galactic nuclei (CL-AGNs), are AGNs that appear to transition between Seyfert Type 1 and 2 over periods of months to years. Several mechanisms to trigger these transitions have been proposed, but we have yet to conclusively determine their cause. Recent studies suggest CL-AGNs are hosted primarily in galaxies that are shutting down star formation (S. A. Dodd et al. 2021; W.-J. Liu et al. 2021; J. Wang et al. 2023), which may indicate a link between galaxy quenching and changing-look events. We use Prospector stellar population synthesis software (B. Johnson &amp; J. Leja 2017; J. Leja et al. 2017; B. D. Johnson et al. 2021) to model nonparametric star formation histories for 39 CL-AGN host galaxies. We find that  43‑12+13%  of our gold sample CL-AGNs at z &lt; 0.15 are star-forming, while  29‑10+13%  fall in the Green Valley of the stellar mass–specific star formation rate diagram. At z &gt; 0.15,  57‑18+13%  of CL-AGNs in the gold sample are star-forming and  29‑14+19%  are in the Green Valley. CL-AGN hosts have similar star formation properties to the host galaxies of Seyfert 1 and 2 AGNs at z &lt; 0.15 and to Seyfert 2 AGNs at z &gt; 0.15. We find no statistically significant differences in the star formation properties of turn-on and turn-off CL-AGNs. We also find no evidence for rapid quenching in the Green Valley CL-AGNs. We conclude that CL-AGN state transitions are not associated with the formation history of CL-AGN host galaxies on large spatial scales, implying CL-AGN state transitions may instead result from nuclear-scale or accretion disk effects.

Keywords: AGN host galaxies, Galaxy quenching, Transient sources, Time domain astronomy
Sleeping Giants Arise: Monitoring the Return of Three Changing-look Quasars to Their High States. Changing-look quasars (CLQs) challenge many models of the quasar central engine. Their extreme variability in both the continuum and broad emission-line fluxes on timescales on the order of years is difficult to explain. To investigate the cause of the observed transitions, we present new contemporaneous optical and X-ray observations of three faded CLQs as they return to a state of high optical luminosity. Two of these three remained in a quiescent state for more than 10 yr before returning to a new high state. We find that before, during, and after transition, the spectral energy distributions of all three follow predictions for quasars based on X-ray binary outbursts, suggesting that the underlying mechanism is likely a changing accretion rate causing changes in the accretion flow structure. In two of the three cases, the transition between the initial high and low state and the transition between the low and new high state took nearly identical amounts of time, on the order of hundreds of days. This transition timescale is a useful constraint on models of the accretion state changes. The behavior of the broad emission-line profiles suggests that the broad-line region structure is changing during the transition. *Based on observations obtained with the Hobby─Eberly Telescope (HET), which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Ludwig-Maximillians-Universitaet Muenchen, and Georg-August Universitaet Goettingen. The HET is named in honor of its principal benefactors, William P. Hobby and Robert E. Eberly.

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

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

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

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

Keywords: X-ray astronomy, Blazars, Active galactic nuclei, Time domain astronomy, Time series analysis
The Growth of Galaxy Stellar Haloes over 0.2 ≤ z ≤ 1.1. Galaxies are predicted to assemble their stellar haloes through the accretion of stellar material from interactions with their cosmic environment. Observations that trace stellar halo buildup probe the processes that drive galaxy size and stellar mass growth. We investigate stellar halo assembly over 0.2 ≤ z ≤ 1.1 in a mass-complete (M⋆ ≥ 109.5M⊙) sample of 242,456 star-forming galaxies (SFGs) and 88,421 quiescent galaxies (QGs) from the CLAUDS and HSC-SSP surveys. We extract galaxy rest-frame g-band surface brightness (μg) profiles to study faint, extended emission in galaxy outskirts. We examine trends in galaxy assembly by analyzing the median μg profiles in different SFG and QG M⋆ ranges with decreasing redshift and connecting evolution in galaxy μg profiles with the underlying stellar mass growth in galaxies. Since z = 1.1, the majority of evolution in the median μg profiles of galaxies (∼64% in SFGs and ∼71% in QGs) occurs throughout their stellar halo regions (2─10 Re). More-massive galaxies assemble stellar halo material more rapidly at 0.2 ≤ z ≤ 1.1. Over this period, QGs grow a larger fraction of their stellar haloes than SFGs at fixed M⋆ (factor of ∼1.2). Although star formation can account for the stellar halo growth observed in low-mass SFGs (109.5M⊙ ≤ M⋆ &lt; 1010.5M⊙), high-mass SFGs (M⋆ ≥ 1010.5M⊙), and both low- and high-mass QGs require an additional assembly mechanism. Our results suggest accretion via minor mergers drives additional stellar halo growth in these galaxies. The contribution from accretion is larger in more-massive galaxies (over M⋆ ≥ 109.5M⊙), and QGs exhibit larger fractional increases to their ex situ fractions over 0.2 ≤ z ≤ 1.1 than SFGs at fixed M⋆.

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

Keywords: Symbiotic binary stars, Stellar winds, Binary stars, Stellar accretion