Sazuna/UAT_keywords huggingface dataset:
Evidence that Mass Loss on the Red Giant Branch Decreases with Metallicity. Mass loss on the red giant branch (RGB) influences stellar evolution, properties of stellar populations, and Galactic chemical enrichment, yet remains poorly constrained observationally. Current models provide limited insight into how stellar properties, particularly how metallicity and mass, affect RGB mass loss. Here, I introduce a new observational approach that uses the age–velocity-dispersion relation and the lower-mass boundary of red giants as precise evolutionary markers. These markers, informed by Galactic evolution, allow us to construct observational isochrones for field stars. By comparing masses of RGB stars and red clump (RC) stars at the same age in the Kepler sample, I derive empirical measurements of integrated RGB mass loss at several points in age and metallicity. Combining these new observational measurements with open-cluster studies, I showed that the integrated mass loss on the RGB decreases with metallicity, and may also decrease with stellar mass. The average mass-loss rate, which accounts for RGB lifetimes and the initial mass differences between RGB and RC stars at the same age, also shows a similar trend. These findings challenge current mass-loss prescriptions widely adopted in stellar evolutionary models, since none of them is able to produce the observed mass-loss trend without widely adjusting free parameters. This highlights an urgent need to revise mechanisms that govern RGB mass loss.

Keywords: Red giant branch, Red giant clump, Open star clusters, Milky Way dynamics, Galactic bulge, Stellar mass loss, Stellar oscillations, Milky Way evolution, Asteroseismology, Rapid stellar oscillations, Milky Way Galaxy
Understanding the Complex Morphology of a Coronal Mass Ejection: Multiview Analysis and Numerical Modeling. Although all coronal mass ejections (CMEs) that propagate into the heliosphere should contain a magnetic flux rope (MFR) component, the majority do not exhibit the expected white-light MFR morphology of a leading edge plus a cavity. This different appearance could be the result of distortion of the internal magnetic structure, merging with other structures, or simply projection effects. These factors complicate the interpretation of CMEs. This complexity is exemplified by a CME observed on 2022 March 28. The event originated from a single eruption, evolving as a textbook CME in the low corona but appearing as a complex two-MFR structure in the white-light observations. Why? To answer this question, we performed a multiview data and modeling analysis to describe the CME coronal evolution. The thermodynamic magnetohydrodynamic model, CORHEL-CME, helps reveal the magnetic configuration of this CME and also reveals that the ambient field plays a crucial role in shaping the complex structure of the CME during early evolution. Our research underscores the importance of integrating multiview observations with physics-based models to gain a deeper insight into the development of complex CMEs.

Keywords: Solar magnetic fields, Solar coronal mass ejections, Heliosphere, Magnetohydrodynamical simulations
Multispacecraft Observations of the 27 Day Periodicity in Galactic Protons from 2018 to 2019. Galactic cosmic-ray (GCR) intensities exhibit recurrent variations caused by their passage through plasma interaction regions corotating with the Sun, with the ∼27 day periodicity being the most prominent one. Data collected by the High-Energy Particle Detector (HEPD-01) on board the China Seismo-Electromagnetic Satellite in Low-Earth Orbit have been used to derive daily proton fluxes from 2018 to 2019 August, in the energy range between ∼55 and ∼200 MeV. Daily fluxes from HEPD-01 have been analyzed along with proton fluxes measured during the same period by ERNE and EPHIN, on board the SOHO spacecraft, and by AMS-02, on board the International Space Station. Using a time-frequency analysis, we confirm a slight energy dependence for the power of the ∼27 day variation as a function of time, with the periodicity maximum occurring earlier for HEPD-01 than for high-energy data from AMS-02. Additionally, as already obtained in previous studies, the rigidity dependence of the amplitude of the aforementioned GCR variation cannot be described by the same power law at both low and high energies, as a consequence of different physical mechanisms playing roles at different rigidity ranges. HEPD-01 GCR measurements cover the energy range from tens to a few hundreds of MeV, which is not accessible to existing detectors (EPHIN and ERNE covering from a few MeV up to tens or a hundred MeV, respectively, and AMS-02 in the GeV–TeV energy range), providing important information for understanding GCR periodicities.

Keywords: Galactic cosmic rays, Cosmic ray detectors, Heliosphere
A Large-scale Ring Galaxy at z = 2.2 Revealed by JWST/NIRCam: Kinematic Observations and Analytical Modelling. A unique galaxy at z = 2.2, zC406690, has a striking clumpy large-scale ring structure that persists from rest-frame UV to near-infrared, yet has an ordered rotation and lies on the star formation main sequence. We combine new JWST/NIRCam and Atacama Large Millimeter/submillimeter Array (ALMA) band 4 observations, together with previous Very Large Telescope/SINFONI integral field spectroscopy and Hubble Space Telescope imaging to reexamine its nature. The high-resolution Hα kinematics is best fitted if the mass is distributed within a ring with total mass Mring ≍ 2 × 1010 M⊙ and radius Rring = 4.6 kpc, together with a central undetected mass component (e.g., a "bulge") with a dynamical mass of Mbulge = 8 × 1010 M⊙. We also consider a purely flux-emitting ring superposed over a faint exponential disk, or a highly "cuspy" dark matter halo, both disfavored against a massive ring model. The low-resolution CO(4─3) line and 142 GHz continuum emission imply total molecular and dust gas masses of Mmol,gas = 7.1 × 1010 M⊙ and Mdust = 3 × 108 M⊙, respectively, over the entire galaxy, giving a dust-to-gas ratio of 0.7%. We estimate that roughly half the gas and dust mass lie inside the ring, and that ∼10% of the total dust is in a foreground screen that attenuates the stellar light of the bulge in the rest-frame UV to near-infrared. Sensitive high-resolution ALMA observations will be essential to confirm this scenario and study the gas and dust distribution.

Keywords: Galaxy mass distribution, Galaxy kinematics, Galaxy evolution, Galaxy rotation curves, High-redshift galaxies
Fundamental Parameters for Central Stars of 103 Infrared Bow Shock Nebulae. Stellar bow shock nebulae are arcuate shock fronts formed by the interaction of radiation-driven stellar winds and the relative motion of the ambient interstellar material. Stellar bow shock nebulae provide a promising means to measure wind-driven mass loss, independent of other established methods. In this work, we characterize the stellar sources at the center of bow shock nebulae drawn from all-sky catalogs of 24 μm–selected nebulae. We obtain new, low-resolution blue optical spectra for 104 stars and measure stellar parameters temperature Teff, surface gravity  logg , and projected rotational broadening  vsini . We perform additional photometric analysis to measure stellar radius R*, luminosity L*, and visual-band extinction AV. All but one of our targets are O and early B stars, with temperatures ranging from T = 16.5 to 46.8 kK, gravities from  logg= 2.57 to 4.60, and  vsini  from &lt;100 to 400 km s‑1. With the exception of rapid rotator ζ Oph, bow shock stars do not rotate at or near critical velocities. At least 60 of 103 (60%) OB bow shock stars are binaries, consistent with the multiplicity fraction of other OB samples. The sample shows a runaway fraction of 23%, with 19 stars having v2D ≥ 25 km s‑1. Of the 19 runaways, at least 15 (≥79%) are binaries, favoring dynamical ejection over the binary supernova channel for producing runaways. We provide a comprehensive census of stellar parameters for bow shock stars, useful as a foundation for determining the mass-loss rates for OB-type stars—one of the single most critical factors in stellar evolution governing the production of neutron stars and black holes.

Keywords: Massive stars, Stellar winds, H II regions, Stellar mass loss
Thermonuclear Supernova Explosion Criteria for Direct and Indirect Collisions of CO White Dwarfs: A Study of the Impact-parameter Threshold for Detonation. The physical collisions of two white dwarfs (WDs; i.e., not slow mergers) have been shown to produce Type Ia–like supernova (SN) explosions. Most studies of WD collisions have focused on zero impact-parameter (direct) collisions, which can also be studied in 2D. However, the vast majority of WD collisions arising from any evolutionary channel suggested to date are expected to be indirect, i.e., have a nonnegligible impact parameter upon collision. Here, we use one of the highest-resolution 3D simulations to date (making use of the AREPO code) in order to explore both direct and indirect collisions and the conditions in which they give rise to a detonation and the production of a luminous SN. Using our simulations, we find a detonation criterion that can provide the critical impact parameter for an explosion to occur, depending on the density profile of the colliding WDs, their composition, and their collision velocities. We find that the initial velocity has a significant impact on the amount of 56Ni production from the explosion. Furthermore, the production of the 56Ni also depends on numerical modeling aspects.

Keywords: Hydrodynamical simulations, Binary stars, Explosive nucleosynthesis, Hydrogen burning, Nuclear astrophysics, Type Ia supernovae, Astrophysical explosive burning, Shocks, Supernova dynamics, Magnetohydrodynamical simulations
Nuclear Spectral Energy Distributions of Luminous Infrared Galaxies. We present nuclear (100─150 pc) spectral energy distributions (SEDs) for a sample of 23 nearby luminous infrared galaxies hosting a total of 28 nuclei. We gather aperture photometry from high-resolution X-ray to submillimeter data for each nuclear region localized by Atacama Large Millimeter/submillimeter Array observations of the dust continuum. We model the broadband SEDs using X-CIGALE. Binning the merging systems by interaction class, we find that the active galactic nucleus (AGN) fraction (fraction of AGN infrared luminosity to total infrared luminosity) appears enhanced in the late- and post-merger stages compared to the early-merger stage. Examining the relationship between X-ray emission and infrared emission of the nuclear regions, we find that the infrared emission in the nuclei is dominated by dust and AGNs, with minimal contribution from stars. We also find that nuclear regions have higher X-ray hardness ratios than the host galaxies globally among both the AGN and non-AGN population. We highlight the similarities and differences in the SEDs of dual nuclei in five closely separated late-stage merging systems: Arp 220 (dnuc ∼ 0.5 kpc), NGC 6240 (dnuc ∼ 1 kpc), IRAS 07251−0248 (dnuc ∼ 2 kpc), IRAS F12112+0305 (dnuc ∼ 4 kpc), and IRAS F14348+1447 (dnuc ∼ 6 kpc). The SEDs for these resolved pairs are distinct, suggesting that the AGN state is much more susceptible to the stellar and dust content within the immediate circumnuclear (&lt;150 pc) environment than to the host's global infrared luminosity or merger stage.

Keywords: Active galaxies, Galaxy interactions, Galaxy nuclei, Galaxy photometry, Infrared galaxies, Spectral energy distribution
Evolution of Steam Worlds: Energetic Aspects. Sub-Neptunes occupy an intriguing region of planetary mass─radius space, where theoretical models of interior structure predict that they could be water-rich, where water is in steam and supercritical state. Such planets are expected to evolve according to the same principles as canonical H2─He rich planets, but models that assume a water-dominated atmosphere consistent with the interior have not been developed yet. Here, we present a state-of-the-art structure and evolution model for water-rich sub-Neptunes. Our setup combines an existing atmospheric model that controls the heat loss from the planet, and an interior model that acts as the reservoir of energy. We compute evolutionary tracks of planetary radius over time. We find that planets with pure water envelopes have smaller radii than predicted by previous models, and the change in radius is much slower (within ∼10%). We also find that water in the deep interior is colder than previously suggested, and can transition from plasma state to superionic ice, which can have additional implications for their evolution. We provide a grid of evolutionary tracks that can be used to infer the bulk water content of sub-Neptunes. We compare the bulk water content inferred by this model and other models available in the literature, and find statistically significant differences between models when the uncertainties on measured mass and radius are both smaller than 10%. This study shows the importance of pursuing efforts in the modeling of volatile-rich planets, and how to connect them to observations.

Keywords: Ocean planets, Hydrosphere, Theoretical models, Ocean-atmosphere interactions, Exoplanet atmospheres, Exoplanet evolution, Exoplanet structure, Planetary interior, Planetary structure
Exploring the Link between Extreme Coronal Line Emitters and Tidal Disruption Events. Galaxies with minimal or no activity from their nucleus can still exhibit significant coronal line (CL) emission, often exceeding the strength of typical narrow emission lines. Many of these CLs require ionization potentials of ≥100 eV, implying the need for intense extreme-ultraviolet and/or soft X-ray flux. Tidal disruption events (TDEs) produced by black holes at galaxy centers are expected to generate such emission lines, yet this link remains underexplored. To evaluate whether CLs are reliable tracers of TDEs, we identified a sample of optical CL galaxies from the Early Data Release of the Dark Energy Spectroscopic Instrument. Our analysis reveals 84 galaxies displaying coronal emission lines among 1.8 million unique targets. Nine sources lie in the active galactic nuclei (AGNs)–starburst composite region and may be AGN-related, so their connection to TDEs remains uncertain. We identified 11 galaxies with spectroscopic coverage in the Sloan Digital Sky Survey, but only 1 exhibits detectable CL variability. We examined the color–magnitude relationship of these extreme coronal line emitters (ECLEs) and found that most are located in the green valley, similar to TDEs. Additionally, our comparison of ECLEs with known TDEs indicates that the stellar mass and star formation rates of ECLE hosts are largely consistent with those of TDE hosts, with many ECLEs also residing within the green valley.

Keywords: Tidal disruption, Emission line galaxies
Dynamics of Multiphase Carbon in the Turbulent Circumgalactic Medium. The circumgalactic medium (CGM) plays a crucial role in regulating material and energy exchange between galaxies and their environments. The best means of observing this medium is through absorption-line spectroscopy, but we have yet to develop a consistent physical model that fully explains the results. Here we investigate the impact of turbulence and nonequilibrium chemistry on the properties of the CGM, using three-dimensional hydrodynamic simulations that include the impact of an ionizing background. Increasing turbulence enhances small-scale density fluctuations, shifting the kinetic energy spectra from Kolmogorov to Burgers scaling. This is indicative of shock-dominated dissipation, which plays a critical role in driving carbon ionization and shaping the multiphase structure of the medium. At the same time, the presence of background radiation significantly alters the ionization balance, increasing the prevalence of C II and C IV. Thus, turbulence and the background radiation have complementary roles: turbulence governs the spatial distribution and facilitates the formation of ionized species, whereas the background radiation modifies the overall ionization equilibrium, setting the observed distribution of multiphase carbon.

Keywords: Extragalactic astronomy, Hydrodynamical simulations, Galaxy chemical evolution, Circumgalactic medium
Exploring the Evolution of Gravitational-wave Emitters with Efficient Emulation: Constraining the Origins of Binary Black Holes Using Normalizing Flows. Binary population synthesis simulations allow detailed modelling of gravitational-wave sources from a variety of formation channels. These population models can be compared to the observed catalogue of merging binaries to infer the uncertain astrophysical input parameters describing binary formation and evolution, as well as the relative rates between various formation pathways. However, it is computationally infeasible to run population synthesis simulations for all variations of uncertain input physics. We demonstrate the use of normalizing flows to emulate population synthesis results and interpolate between astrophysical input parameters. Using current gravitational-wave observations of binary black holes, we use our trained normalizing flows to infer branching ratios between multiple formation channels, and simultaneously infer common-envelope efficiency and natal spins across a continuous parameter range. Given our set of formation channel models, we infer the natal spin to be  0.04‑0.01+0.04 , and the common-envelope efficiency to be &gt;3.7 at 90% credibility, with the majority of underlying mergers coming from the common-envelope channel. Our framework allows us to measure population synthesis inputs where we do not have simulations, and better constrain the astrophysics underlying current gravitational-wave populations.

Keywords: Bayesian statistics, Multiple star evolution, Astrostatistics techniques, Stellar mass black holes, Gravitational wave sources, Gravitational wave astronomy
Shaping the Milky Way: The Interplay of Mergers and Cosmic Filaments. The large-scale morphology of Milky Way (MW)–mass dark matter halos is shaped by two key processes: filamentary accretion from the cosmic web and interactions with massive satellites. Disentangling their contributions is essential for understanding galaxy evolution and constructing accurate mass models of the MW. We analyze the time-dependent structure of MW-mass halos from zoomed cosmological-hydrodynamical simulations by decomposing their mass distribution into spherical harmonic expansions. We find that the dipole and quadrupole moments dominate the gravitational power spectrum, encoding key information about the halo's shape and its interaction with the cosmic environment. While the dipole reflects transient perturbations from infalling satellites and damps on dynamical timescales, the quadrupole—linked to the halo's triaxiality—is a persistent feature. We show that the quadrupole's orientation aligns with the largest filaments, imprinting a long-lived memory on the halo's morphology even in its inner regions (∼30 kpc). At the virial radius, the quadrupole distortion can reach 1–2 times the spherical density, highlighting the importance of environment in shaping MW-mass halos. Using multichannel singular spectrum analysis, we successfully disentangle the effects of satellite mergers and filamentary accretion on quadrupole. We find that, compared to isolated MW–LMC simulations that typically use a spherical halo, the LMC-mass satellite induces a quadrupolar response that is an order of magnitude larger in our cosmological halo. This highlights the need for models that incorporate the MW's asymmetry and time evolution, with direct consequences for observable structures such as disk warps, the LMC-induced wake, and stellar tracers—particularly in the era of precision astrometry.

Keywords: Galaxy dark matter halos
A 3D Model of the Local Bubble's Magnetic Field: Insights from Dust and Starlight Polarization. Clustered stellar feedback creates expanding voids in the magnetized interstellar medium known as superbubbles. Although theory suggests that superbubble expansion is influenced by interstellar magnetic fields, direct observational data on 3D superbubble magnetic field geometry is limited. The Sun's location inside the Local Bubble provides a unique opportunity to infer a superbubble's 3D magnetic field orientation, under the assumptions that: (I) the Local Bubble's surface is the primary contributor to plane-of-the-sky polarization observations across much of the sky, and (II) the Local Bubble's magnetic field is tangent to its dust-traced shell. In this work, we validate these assumptions and construct a model of the Local Bubble's 3D B-field orientation from Planck 353 GHz polarization observations and a 3D-dust-derived model of the Local Bubble's shell. We test Assumption I by examining correlations between the Local Bubble's 3D geometry, dust polarization, and starlight polarization. We find that the Local Bubble likely dominates the polarized signal in the majority of lines of sight. We jointly test Assumptions I and II by applying our reconstruction method to a simulated superbubble, where we successfully reconstruct the 3D magnetic field orientation over the bulk of its surface. Finally, we use our 3D B-field model to infer the initial magnetic field orientation in the solar neighborhood prior to the Local Bubble's formation, and derive an orientation parallel to the present-day Local Arm of the galaxy. These findings provide new insights into the coevolution of superbubbles and the magnetized interstellar medium.

Keywords: Interstellar dust, Solar neighborhood, Interstellar magnetic fields, Starlight polarization, Interstellar medium, Superbubbles
Ultraviolet Variability in Solar-type Members of the M67 Open Cluster. Solar-type members of the rich, nearly solar-age and solar-metallicity M67 open cluster are systematically investigated for ultraviolet variability. We utilize archival Galaxy Evolution Explorer (GALEX) data, which feature several imaging observation epochs spanning 5 yr. Stars in or suspected of being in binary systems are avoided as well as stars that are blended in GALEX data, leading to a sample of 66 solar-type stars. We assess variability over a variety of timescales that probe flares and longer-term trends that could be due to rotation and activity cycles. We do not find conclusive evidence for variability and determine that solar-type members of M67 do not display &gt;30% near-ultraviolet (NUV) variability over timescales ranging from days to years. Furthermore, within 50 s cadence lightcurves generated for each of the imaging epochs we find no NUV flares that are ≳2× the quiescent stellar NUV emission level; the implied ultraviolet flare rate derived from this study is in mild tension with that derived for stars observed by GALEX in the primary Kepler field. This M67 GALEX study presents one of the most comprehensive ultraviolet data sets currently available for probing continuum emission variability for old Sun-like stars; the planned NASA UVEX mission has the potential to dramatically expand upon this work.

Keywords: Ultraviolet astronomy, G dwarf stars, Stellar activity