Sazuna/UAT_keywords huggingface dataset:
Backmapping of the High- and Low-latitude Solar Wind under Multiple Heliospheric and Coronal Magnetic Field Configurations. Solar wind backmapping is a critical technique for analyzing the origin of the solar wind and space weather events by correlating in situ measurements with solar remote-sensing observations. This technique typically traces magnetic field lines using a heliospheric magnetic field (HMF) model coupled with a coronal magnetic field (CMF). However, the impact of different HMF and CMF configurations on backmapping uncertainty—particularly regarding high-latitude solar wind—remains inadequately quantified. This study comprehensively evaluates solar wind backmapping by combining two HMF models (Parker spiral, Fisk-type) with three CMF models (potential field source surface (PFSS), potential field current sheet (PFCS), current sheet source surface (CSSS)). Our analysis primarily uses in situ measurements from Ulysses and remote-sensing data from STEREO-A. Key findings are that: (1) While both Fisk and Parker HMF models show comparable consistency with measured magnetic field strength and polarity, they produce certain longitudinal displacements in their backmapped footpoints on the source surface (2.5R⊙); (2) For CMF models (PFSS, PFCS, CSSS), predicted photospheric footpoints exhibit minor variations for high-/midlatitude solar wind but some divergences for ecliptic/low-latitude wind; (3) All three CMF models link high-/midlatitude wind to active regions or coronal holes, yet associate a fraction of ecliptic/low-latitude wind with quiet-Sun regions; (4) Ecliptic/low-latitude sources show significantly stronger dependence on the PFSS source surface height compared to high-latitude wind. These results demonstrate that simpler models (PFSS + Parker) appear reasonably adequate for polar coronal hole wind studies, while low-latitude/ecliptic solar wind exhibits the heightened sensitivity to model choices.

Keywords: Solar wind, Magnetic fields, Solar corona, Heliosphere
Estimate of Current Mass of the Large Magellanic Cloud from the Orphan─Chenab Tidal Stream. By fitting the tilt in the path of the Orphan─Chenab Stream (OCS), we conclude that the current mass of the Large Magellanic Cloud (LMC) within 30 kpc is (4.7─5.1) × 1010 M⊙. We note that the tidal radius of the LMC of this mass is 16.9 kpc, indicating that our measured mass approximates the current bound mass of the LMC. Previous measurements of the LMC mass based on fitting the observed path of the OCS through the Milky Way (MW) halo reported the total mass of the LMC. We show that because the closest approach of the LMC to the OCS, where the gravitational perturbation of the stream path is the highest, is about 20 kpc, the mass of the LMC outside 30 kpc is not constrained and depends entirely on the assumed radial profile at large radius. Our best-fit total mass varies between 4.5 × 1010 and 2.2 × 1011 M⊙ or more, depending on the presumed radial profile of the LMC. We also show that previous measurements of the mass of the LMC that used a particle-spray method to simulate the path of the OCS suffered from systematic error because they assumed that all particles were stripped from the dwarf galaxy at the tidal radius; N-body simulations show that particles are actually released from a range of distances from the center of mass of the OCS. In contrast, the choice of MW potential has little effect on the LMC mass estimated from the OCS.

Keywords: Stellar streams, Galaxy structure, Dwarf galaxies, Milky Way dynamics, Large Magellanic Cloud, Galaxy kinematics
Dwarf Active Galactic Nuclei from Variability for the Origins of Seeds (DAVOS): Properties of Variability-selected AGN in the Dark Energy Survey Deep Fields. We study the black hole mass─host galaxy stellar mass relation, MBH─M*, for a sample of 706 z ≲ 1.5 and i ≲ 24 optically variable active galactic nuclei (AGNs) in three Dark Energy Survey (DES) Deep Fields: C3, X3, E2, which partially cover Chandra Deep Field-South, XMM Large Scale Structure survey, and European Large Area ISO Survey, respectively. The parent sample was identified by optical variability from the DES supernova survey program imaging. Using publicly available spectra and photometric catalogs, we consolidate their spectroscopic redshifts, estimate their black hole masses using broad line widths and luminosities, and obtain improved stellar masses using spectral energy distribution fitting from X-ray to mid-infrared wavelengths. Our results confirm previous work from Hyper-Suprime Camera imaging that variability searches with deep, high-precision photometry can reliably identify AGNs in low-mass galaxies up to z ∼ 1. However, we find that the hosted black holes are more massive than predicted by the local AGN relation, fixing host galaxy stellar mass. Instead, z ∼ 0.1─1.5 variability-selected AGNs lie in between the MBH─M* relation for local inactive early-type galaxies and local active galaxies. This result agrees with most previous studies of the MBH─M* relation for AGNs at similar redshifts, regardless of the selection technique. We demonstrate that studies of variability-selected AGN provide critical insights into the low-mass end of the MBH─M* relation, shedding light on the occupation fraction of that provides constraints on early black hole seeding mechanisms and self-regulated feedback processes during their growth and coevolution with their hosts.

Keywords: Black holes, Surveys, Active galaxies, Dwarf galaxies, Galaxy nuclei, Active galactic nuclei
Gravitational Redshift for Rapidly Rotating Neutron Stars. The oblate Schwarzschild (OS) approximation is a method often used to compute the flux of X-rays emitted from a rapidly rotating neutron star. In this approximation, the oblate shape of the rotating star is embedded in the Schwarzschild metric, which is used to compute the redshift of photon energies as they propagate from the star to the telescope. In this paper, we demonstrate that there are small errors introduced by the standard treatment of photon redshift in the OS approximation and provide a simple method to correct these errors. These errors are constant in phase, so this results in a constant absolute reduction in the flux. For PSR J0740+6620, the most rapidly spinning of the pulsars observed by the Neutron star Interior Composition Explorer (NICER), we estimate the flux errors are less than 1%, which is an order of magnitude smaller than the uncertainty in the distance, so this does not affect the mass and radius constraints found for this pulsar. The errors for the other pulsars observed by NICER are even smaller. However, this correction should be included when analyzing data for more rapidly rotating X-ray pulsars with spin frequencies near 600 Hz.

Keywords: Neutron stars, Relativistic stars, Rotation powered pulsars, Pulsars, General relativity
Buildup, Explosion, and Untwisting of a Solar Active Region Jet Observed with Solar Orbiter, IRIS, and SDO. We present detailed analysis of an active region coronal jet accompanying a minifilament eruption that is fully captured and well resolved in high spatial resolution 174 Å coronal images from Solar Orbiter's Extreme Ultraviolet Imager (EUI). The active region jet is simultaneously observed by the Interface Region Imaging Spectrograph and the Solar Dynamics Observatory. An erupting minifilament is rooted at the edge of an active region where mixed-polarity magnetic flux is present. Minority-polarity positive flux merges and cancels with the active region's dominant negative flux at an average rate of 1019 Mx hr−1, building a minifilament-holding flux rope and triggering its eruption. The eruption shows a slow rise followed by a fast rise, akin to large-scale filament eruptions. EUI images and Mg II k spectra, displaying simultaneously blueshift and redshift at the opposite edges of the spire, indicate counterclockwise untwisting of the jet spire. This jet is the clearest, most comprehensively observed active-region jet with this instrument set, displaying striking similarities with quiet Sun and coronal hole jets. Its magnetic (≤1028 erg), thermal (1025 erg), and kinetic (1025 erg) energies suggest a significant contribution to local coronal heating. We conclude that magnetic flux cancelation builds a minifilament-carrying twisted flux rope and also eventually triggers the flux rope's eruption that makes the coronal jet, in line with our recent results on the buildup and explosion of solar coronal jets in quiet Sun and coronal holes. That is, this active region jet clearly works the same way as the vast majority of quiet Sun and coronal hole jets.

Keywords: Jets, Solar ultraviolet emission, Solar magnetic reconnection, Solar magnetic fields, Spectroscopy, Solar corona
α-MC: Self-consistent α-enhanced Stellar Population Models Covering a Wide Range of Age, Metallicity, and Wavelength. We present new stellar population models, α-MC, self-consistently taking into account nonsolar [α/Fe] abundances for both isochrones and stellar spectra. The α-MC models are based on α-enhanced MIST isochrones and C3K spectral libraries, which are publicly available in FSPS. Our new models cover a wide range of ages ( log(age/yr)=5.0-10.3 ), metallicities ([Fe/H] = [−2.5, +0.5] in steps of 0.25, [α/Fe] = −0.2, +0.0, +0.2, +0.4, +0.6), and wavelengths (0.1─2.5 μm). We investigate the separate and combined effects of α-enhanced isochrones and stellar spectral libraries on simple stellar populations, including their broadband colors, spectral indices, and full spectra. We find that the primary effect of α-enhancement in isochrones is to lower the overall continuum levels and redden the continuum shapes, while α-enhancement in stellar spectra mainly affects individual spectral lines. At constant [Fe/H], α-enhancement has significant impacts on the broadband colors by ∼0.1─0.4 mag across all ages (0.01─10 Gyr). The effects of α-enhancement on colors at fixed [Z/H] are smaller, by ∼0.1─0.2 mag. The spectral indices involving α-elements, Ca4227 and Mg b, increase with [α/Fe] (both at fixed [Fe/H] and fixed [Z/H]) due to enhanced α-abundances. At constant [Fe/H], α-enhancement weakens most Fe-sensitive and hydrogen Balmer lines. Our new self-consistent α-enhanced models will be essential in deriving accurate physical properties of high-redshift galaxies, where α-enhancement is expected to be common.

Keywords: Stellar populations, Spectral energy distribution, Galaxies
Utilizing Maximum Variability to Discern TDE Emission from AGN Flares. X-ray emission arising from active galactic nucleus (AGN) activity may potentially mimic the expected emission of tidal disruption events (TDEs). Ongoing and upcoming wide-field X-ray surveys will detect thousands of TDE-like sources, and classifying them securely as TDEs or AGNs is a challenging task. To this aim, we measure the average X-ray variability of AGNs and derive a threshold of maximum variation as a function of time separating the TDEs from AGN flares. For the comparison between TDE and AGN X-ray variability, we cross-match the publicly available XMM-Newton and Swift-XRT point-source catalogs with the Million Quasars Catalog and optically selected TDEs. Then we compute the X-ray structure function (SF) and maximum variability of the AGN and TDE samples. The X-ray SF of AGNs has a power-law index γ ∼ 0.11─0.14 when fitted with a simple power-law model. However, the SF of AGNs is best described by a broken power law or a power exponential model with a damping timescale τ = 950 ± 300 days. The maximum variability comparison between TDE and simulated AGN light curves indicates they have a similar order of variation on a timescale of less than 20 days. However, at a longer timescale of ∼20 days or more, the large-scale variations expected from power-law-like decay in TDEs become less frequent in AGNs. Furthermore, we compare the maximum variability of eROSITA TDE candidates with AGNs, finding that many of the eROSITA-DE TDE candidates are consistent with flares from AGNs and may not be TDEs.

Keywords: Tidal disruption, Active galaxies, X-ray active galactic nuclei, Quasars
A Novel Test for MOND: Gravitational Lensing by Disk Galaxies. Disk galaxies represent a promising laboratory for the study of gravitational physics, including alternatives to dark matter (DM), owing to the possibility of coupling rotation curves' dynamical data with strong gravitational lensing (SGL) observations. In particular, Euclid, DES, and LSST are predicted to observe hundreds of thousands of gravitational lenses. Here, we investigate disk galaxy SGL in the modified Newtonian dynamics (MOND) framework. We employ the concept of equivalent Newtonian systems within the quasi-linear MOND formulation to make use of the standard lensing formalism. We derive the phantom DM distribution predicted for realistic disk galaxy models and study the impact of morphological and mass parameters on the expected lensing. We find purely MONDian effects dominate the lensing—due to the presence of a phantom DM disk—and generate nontrivial correlations between the lens parameters and the lensing cross section. Moreover, we show that MOND predicts a substantial increase in the number count of disk galaxy lenses compared to the DM-driven predictions, making it distinguishable from the latter in upcoming surveys regardless of the chosen interpolating function. Finally, we argue that disk galaxy gravitational lensing, coupled to additional astronomical observations, can be used to constrain the interpolating function of MOND.

Keywords: Gravitation, Strong gravitational lensing, Modified Newtonian dynamics, Disk galaxies
Preferential Accretion onto the Secondary Black Hole Strengthens Gravitational-wave Signals. Pulsar timing arrays have recently found evidence for nanohertz gravitational waves that are consistent with being produced by a cosmological population of binary supermassive black holes (SMBHs). However, the amplitude of this gravitational-wave background is larger than predicted from theoretical and empirical models of SMBH binary populations. We investigate preferential accretion onto the secondary, less massive SMBH of the binary as a potential solution to this discrepancy. We carry out the first observationally based analysis of the effect of preferential accretion on the SMBH binary population, and we find that preferential accretion onto the secondary SMBH increases the binary SMBH mass ratio, causing many minor galaxy mergers to lead to major SMBH mergers. The fraction of SMBH mergers that are major mergers increases by a factor of 2─3 when preferential accretion is included. Further, we find that only a small amount of preferential accretion (10% total SMBH mass growth) is needed to bring the predicted gravitational-wave background amplitude into agreement with observations. Preferential accretion has an even larger effect on gravitational-wave signals detected by LISA, which will probe SMBH binaries at higher redshifts where the environment is more gas-rich, and can also help explain the rapid buildup of overmassive black holes at high redshifts observed by the James Webb Space Telescope. It also shortens the time to the first detection of an individual SMBH binary emitting continuous waves. Preferential accretion strengthens the gravitational-wave signals produced by any binary embedded in a circumbinary disk, including LIGO sources.

Keywords: Accretion, Supermassive black holes, Galaxy mergers, Gravitational waves, Astrophysical black holes
GX 340+0: In and Out of Focus. The Nuclear Spectroscopic Telescope Array (NuSTAR) enables detailed high-energy X-ray observations from 3─79 keV, but its performance can be constrained by telemetry saturation when observing bright sources, leading to reduced effective exposure times. In this study, we investigate the use of serendipitous stray light (SL) observations to infer properties of an X-ray bright source in comparison to focused data. Our case study is performed on the neutron star low-mass X-ray binary GX 340+0, a prominent Z source, where we execute a spectral analysis comparing 25 SL and 7 focused NuSTAR observations. Our findings demonstrate that SL observations can significantly enhance long-term temporal coverage detecting variations in the thermal components of the system across the baseline of the mission, which could not be inferred from focused observations alone.

Keywords: Low-mass x-ray binary stars, Neutron stars, Accretion
The AURORA Survey: Tracing Galactic Outflows at z ≳ 2.5 with JWST/NIRSpec Near-ultraviolet Absorption Lines. We probe galactic-scale outflows in star-forming galaxies at z ≳ 2.5 drawn from the JWST/NIRSpec AURORA program. For the first time, we directly compare outflow properties from the early Universe to the present day using near-UV absorption lines. We measure interstellar medium (ISM) kinematics from Fe II and Mg II absorption features in 41 and 43 galaxies, respectively, and examine how these kinematics correlate with galaxy properties. We find that galaxies with outflows tend to have higher stellar masses and that maximum outflow velocities increase with stellar mass, star formation rate (SFR), UV slope β, E(B − V), and AV. We also find that Mg II emission is more common in galaxies with lower masses, higher specific SFRs, and less dust. These trends are consistent with those in star-forming galaxies at z &lt; 2 when using the same outflow tracers, suggesting that the feedback from star formation has played a persistent role in shaping galaxy evolution over cosmic time. We also directly compare near-UV and far-UV features in the same NIRSpec spectrum for a z = 5.19 galaxy, finding consistent ISM kinematics and demonstrating that different tracers yield comparable measurements. We also detect Na D absorption in 10 galaxies, which have higher stellar mass, SFR, and dust attenuation compared to galaxies without Na D absorption, which is consistent with z ∼ 0 studies. The broad continuum coverage and sensitivity of NIRSpec will enable future studies with larger samples, allowing for robust tests of these trends across a wider dynamic range of galaxy properties.

Keywords: James Webb Space Telescope, Galaxy kinematics, Galaxy evolution
Lost in the FoG: Pitfalls of Models for Large-scale Hydrogen Distributions. Large-scale H I surveys and their cross correlations with galaxy distributions have immense potential as cosmological probes. Interpreting these measurements requires theoretical models that must incorporate redshift-space distortions (RSDs), such as the Kaiser and fingers-of-God (FoG) effect, and differences in the tracer and matter distributions via the tracer bias. These effects are commonly approximated with assumptions that should be tested on simulated distributions. In this work, we use the hydrodynamical simulation suite IllustrisTNG to assess the performance of models of z ≤ 1 H I autopower and H I-galaxy cross-power spectra, finding that the models employed by recent observations introduce errors comparable to or exceeding their measurement uncertainties. In particular, neglecting FoG causes ≳10% deviations between the modeled and simulated power spectra at k ≳ 0.1 h cMpc−1, larger than assuming a constant bias that reaches the same error threshold at slightly smaller scales. However, even without these assumptions, models can still err by ∼10% on observationally relevant scales. These remaining errors arise from multiple RSD damping sources on H I clustering, which are not sufficiently described with a single FoG term. Overall, our results highlight the need for an improved understanding of RSDs to harness the capabilities of future measurements of H I distributions.

Keywords: Cosmology, Hydrodynamical simulations, Galaxy formation, Large-scale structure of the universe, Clustering, Hierarchical cosmology, Astronomical simulations
Signatures of Black Hole Seeding on the M<SUB>∙</SUB>─σ Relation: Predictions from the BRAHMA Simulations. The James Webb Space Telescope has identified a large population of supermassive (106─108 M⊙) black holes (BHs) in the early Universe (z ∼ 4─7). Current measurements suggest that many of these BHs exhibit higher BH-to-stellar mass ratios than local populations, opening a new window into the earliest stages of BH─galaxy coevolution and offering the potential to place tight constraints on BH seeding and growth in the early Universe. In this work, we use the BRAHMA simulations to investigate the impact of BH seeding on the M∙─σ relation. These simulations adopt heavy ∼105 M⊙ seeds and systematically varied BH seeding models, resulting in distinct predictions for seed abundances. We find that different seed models lead to different normalizations of the M∙─σ relation at higher redshifts (z &gt; 2) across all σ, and at low redshift for systems with low σ (50 km s−1 ≲ σ ≲ 80 km s−1). The most lenient seed model also shows negligible evolution in the M∙─σ relation across redshift, while more restrictive models have substantially lower normalization on the M∙─σ relation for high σ (∼100 km s−1) at high redshifts, and evolve upward toward the local relation. We demonstrate that, while an evolving M*─σ relation mitigates changes in the M∙─σ relation, any M∙─σ evolution is a direct consequence of merger-dominated BH growth in low mass galaxies (≲109 M⊙) and accretion-dominated BH growth in high-mass (≳109 M⊙) galaxies. Furthermore, the scatter in the M∙─σ relation is larger for the more restrictive models due to the inability of many BHs to grow significantly beyond their seed mass.

Keywords: Supermassive black holes, Hydrodynamical simulations, Scaling relations
Time-dependent Turbulent Electron Acceleration and Transport in Solar Flares. Solar flares are explosive releases of magnetic energy stored in the solar corona, driven by magnetic reconnection. These events accelerate electrons, generating hard X-ray emissions, and often display quasi-periodic pulsations (QPPs) across the energy spectra. However, the energy transfer process remains poorly constrained, with competing theories proposing different acceleration mechanisms. We investigate electron acceleration and transport in a flaring coronal loop by solving a time-dependent Fokker─Planck equation. Our model incorporates transient turbulent acceleration, simulating the effects of impulsive energy input to emulate the dynamics of time-dependent reconnection processes. We compute the density-weighted electron flux, a diagnostic directly comparable to observed X-ray emissions, across the energy and spatial domains from the corona to the chromosphere. We investigate different time-dependent functional forms of the turbulent acceleration, finding that the functional form of the acceleration source maintains its signature across energy bands (1─100 keV) with a response time that is energy dependent (with higher-energy bands displaying longer response times). In addition, we find that (a) for a square pulse the switch on and off response time is different; (b) for a sinusoidal input the periodicity is preserved; and (c) for a damped sinusoidal the decay rate increases with density and higher-energy bands lose energy faster. This work presents a novel methodology for analyzing electron acceleration and transport in flares driven by time-dependent sources.

Keywords: Solar atmosphere, Solar flares, Solar energetic particles, The Sun, Solar corona, Solar x-ray flares, Solar chromosphere