Sazuna/UAT_keywords huggingface dataset:
paired: A Statistical Framework for Detecting Stellar Binarity with Gaia RVs. I. Sensitivity to Unresolved Binaries. Data Release 3 (DR3) from the Gaia Mission includes radial velocity measurements of over 33 million targets. Among many scientific applications, the overlap of this stellar sample with targeted exoplanet transit survey stars presents an opportunity to understand planet occurrence in the context of stellar multiplicity on a large scale. Yet, any interpretation of occurrence relies upon an understanding of survey sensitivity. While the sensitivity to planets in transit surveys is well-understood, a characterization of the sensitivity of Gaia to unresolved binaries is also critical. We describe here a statistical framework called paired, which we developed to enable the forward modeling of Gaia radial velocity observables for large samples of stars. The paired machinery links the reported radial velocity noise for a given star from Gaia to the probability of a spatially unresolved stellar companion. We demonstrate how this enables the user, given an observed distribution of individual binary "probabilities" for a set of stars, to understand this distribution within the sensitivity limits of Gaia. For the subset of stars with the highest probability of excess radial velocity noise, we describe the ability of paired to constrain the semi-amplitude of the stellar binary. Where possible, we benchmark our inferred radial velocity semi-amplitudes against those from ground-based radial velocity surveys, as well as the subset published by Gaia DR3 itself. We aim for paired to be a community tool for the exploration of the effects of binarity on planets at a population level, but also for any user interested in stellar populations.

Keywords: Astrostatistics tools, Binary stars, Close binary stars, Astrostatistics, Spectroscopic binary stars
Magnetic Fields in the Eos Cloud: Dynamically Important Fields in the Interface between Atomic and Molecular Gas. The recently discovered Eos molecular cloud is a CO-dark, low-density cloud located at a distance of approximately 94 pc from the Sun which does not appear to have formed stars at any point in its history. In this paper, we investigate the magnetic fields in the Eos cloud, near the interface between the atomic cold neutral medium (CNM) and molecular gas, using dust emission and extinction polarimetry. A histogram of relative orientation analysis shows that the magnetic field is preferentially parallel to the density structure of the cloud, while a Davis─Chandrasekhar─Fermi analysis finds magnetic field strengths of 6 ± 3 μG across the Eos cloud and 12 ± 4 μG in the somewhat denser MBM 40 subregion. These results are consistent with a previous estimate of magnetic field strength in the Local Bubble and suggest that the fields in the Eos cloud are dynamically important compared to both gravity and turbulence. Our findings are fully consistent with the expected behavior of magnetized, non-self-gravitating gas near the CNM/molecular cloud boundary.

Keywords: Interstellar dust, Magnetic fields, Molecular clouds, Interstellar medium
Prospects of Constraining Equilibrium Tides in Low-mass Binary Stars. The dynamical evolution of short-period low-mass binary stars (with mass M &lt; 1.5M⊙, from formation to the late main sequence, and with orbital periods less than ∼10 days) is strongly influenced by tidal dissipation. This process drives orbital and rotational evolution that ultimately results in circularized orbits and rotational frequencies synchronized with the orbital frequency. Despite the fundamental role of tidal dissipation in binary evolution, constraining its magnitude (typically parameterized by the tidal quality factor  Q ) has remained discrepant by orders of magnitude in the existing literature. Recent observational constraints from time-series photometry (e.g., Kepler, K2, TESS), as well as advances in theoretical models to incorporate a more realistic gravitational response within stellar interiors, are invigorating new optimism for resolving this long-standing problem. To investigate the prospects and limitations of constraining tidal  Q , we use global sensitivity analysis and simulation-based inference to examine how the initial conditions and tidal  Q  influence the observable orbital and rotational states. Our results show that, even under the simplest and most tractable models of tides, the path toward inferring  Q  from individual systems is severely hampered by inherent degeneracies between tidal  Q  and the initial conditions, even when considering the strongest possible constraints (i.e., binaries with precise masses, ages, orbital periods, eccentricities, and rotation periods). Finally, as an alternative, we discuss how population synthesis approaches may be a more promising path forward for validating tidal theories.

Keywords: Close binary stars, Low mass stars, Tidal interaction, Stellar rotation, Stellar evolution
The ODYSSEUS Survey. Characterizing Magnetospheric Geometries and Hotspot Structures in T Tauri Stars. Magnetospheric accretion is a key process that shapes the inner disks of T Tauri stars, controlling mass and angular momentum evolution. It produces strong ultraviolet and optical emission that irradiates the planet-forming environment. In this work, we characterize the magnetospheric geometries, accretion rates, extinction properties, and hotspot structures of 67 T Tauri stars in the largest and most consistent study of ultraviolet and optical accretion signatures to date. To do so, we apply an accretion flow model to velocity-resolved Hα profiles for T Tauri stars from the Hubble Space Telescope (HST) ULLYSES program with consistently derived stellar parameters. We find typical magnetospheric truncation radii to be almost half of the usually assumed value of 5 stellar radii. We then model the same stars' HST/STIS spectra with an accretion shock model, finding a diverse range of hotspot structures. Phase-folding multiepoch shock models reveals rotational modulation of observed hotspot energy flux densities, indicative of hotspots that persist for at least three stellar rotation periods. For the first time, we perform a large-scale, self-consistent comparison of accretion rates measured using accretion flow and shock models, finding them to be consistent within ∼0.16 dex for contemporaneous observations. Finally, we find that up to 50% of the total accretion luminosity is at short wavelengths accessible only from space, highlighting the crucial role of ultraviolet spectra in constraining accretion spectral energy distributions, hotspot structure, and extinction.

Keywords: Ultraviolet spectroscopy, H I line emission, T Tauri stars, Pre-main sequence stars, Protoplanetary disks, Stellar accretion
Cosmic-Ray Mass Composition around the Knee via Principal Component Analysis. In this paper, we apply principal component analysis (PCA) to experimental data recorded by the KASCADE experiment to reconstruct the mass composition of cosmic rays around the knee region. A set of four extensive air shower parameters sensitive to the primary particle mass (LCm, Nμ, Ne, and lateral shower age) was considered, whose coordinates were transformed into a new orthogonal basis that maximally captures the data variance. Based on the experimental distributions of the first two principal components (PCA0 versus PCA1) and full Monte Carlo simulations of the KASCADE array considering five types of primary particles (p, He, C, Si, and Fe) and three hadronic interaction models (EPOS-LHC, QGSjet-II-04, and SIBYLL 2.3d), we obtained the evolution of the abundance of each primary species as a function of energy, as well as the evolution of the mean logarithmic mass with energy. We found that the reconstruction of the mass composition resulting from this comprehensive analysis significantly reduces dependence on the hadronic interaction model used in the simulation process, even though the initial input parameters are model dependent. Moreover, the results support the idea that around the knee region, the abundance of the light component (protons) decreases, while the heavy component shows a slight increase. The evolution of  &lt;ln(A)&gt;  as a function of energy derived from this analysis shows excellent agreement with recent results from the LHAASO–KM2A experiment and aligns very well with the predictions of the data-driven Global Spline Fit model.

Keywords: High-energy cosmic radiation
A Novel Formation Channel for Supermassive Black Hole Binaries in the Early Universe via Primordial Black Holes. We present a novel formation channel for supermassive black hole (SMBH) binaries in the early Universe, driven by primordial black holes (PBHs). Using high-resolution hydrodynamical simulations, we explore the role of massive PBHs (mBH ∼ 106 M⊙) in catalyzing the formation of direct-collapse black holes (DCBHs), providing a natural in situ pathway for binary SMBH formation. PBHs enhance local overdensities, accelerate structure formation, and exert thermal feedback on the surrounding medium via accretion. Lyman–Werner radiation from accreting PBHs suppresses H2 cooling, shifting the dominant gas coolant to atomic hydrogen. When combined with significant baryon–dark matter streaming velocities (vbχ ≳ 0.8σbχ, where σbχ is the rms streaming velocity), these effects facilitate the formation of dense, gravitationally unstable atomically cooling gas clouds in the PBH's wake. These clouds exhibit sustained high inflow rates ( Ṁinfall≳0.1‑0.01M⊙  yr‑1), providing ideal conditions for DCBH formation from rapidly growing supermassive stars of ∼105 M⊙ at redshift z ∼ 20–10. The resulting systems form SMBH binaries with initial mass ratios  q∼O(0.1)  and separations of ∼10 pc. Such PBH-DCBH binaries provide testable predictions for JWST and Atacama Large Millimeter/submillimeter Array, potentially explaining select high-z sources like little red dots, and represent gravitational-wave sources for future missions like LISA and TianQin—bridging early-Universe black hole physics, multimessenger astronomy, and dark matter theory.

Keywords: Early universe, Galaxy formation, Supermassive black holes, Population III stars, Dark matter
Confined Circumstellar Material as a Dust Formation Site in Type II Supernovae. We propose a model for dust formation in Type II supernovae (SNe) interacting with confined circumstellar material (CSM), motivated by recent time-domain surveys that have revealed a substantial fraction of SN progenitors to be surrounded by CSM ejected shortly before core collapse. We simulate the pre-SN mass eruption and the resulting confined CSM using the open-source code CHIPS, and follow the subsequent evolution of the SN ejecta and its interaction with the CSM. We show that a cold dense shell (CDS) is formed at the radiative shock under a wide range of conditions and later undergoes rapid adiabatic cooling during free expansion, leading to efficient dust condensation. The resulting dust mass ranges from ∼10‑3 M⊙ to 0.1 M⊙, depending on the mass and spatial extent of the CSM. We further calculate the infrared (IR) emission from the newly formed dust and find broad consistency with observations of SN 1998S. Notably, the IR light curve exhibits a rapid rise within ≲10 days, closely resembling that of kilonovae (KNe). This suggests that dust emission powered by confined CSM interaction may be also discovered in KN searches. Moreover, the high-density environment of the CDS may allow dust grains to grow to larger sizes, enhancing their survivability against destruction by reverse shocks propagating from the interstellar medium at later times.

Keywords: Interstellar dust, Circumstellar matter, Supernovae, Stellar mass loss
Selection of Dwarf Galaxies Hosting Active Galactic Nuclei: A Measure of Bias and Contamination Using Unsupervised Machine Learning Techniques. Identifying active galactic nuclei (AGNs) in dwarf galaxies is critical for understanding black hole formation but remains observationally challenging due to their low luminosities, metallicities, and star formation─driven emission that can obscure AGN signatures. Machine learning techniques, particularly unsupervised methods, offer new ways to address these challenges by uncovering patterns in complex, multiwavelength data. In this study, we apply Self-Organizing Maps (SOMs) to explore the spectral energy distribution (SED) manifold of dwarf galaxies and evaluate AGN selection biases across various diagnostics. We train a 51 × 51 SOM on 30,344 dwarf galaxies (z &lt; 0.055, M* &lt; 109.5M⊙) from the NSA catalog using nine-band photometry spanning near-UV to mid-infrared. A set of 438 previously identified dwarf AGNs, selected via mid-infrared color, optical emission lines, X-ray, optical variability, and broad-line features, was mapped onto the SOM. AGNs identified by different methods occupy distinct and partially overlapping regions in SED space, reflecting biases related to host galaxy properties. Wide-field Infrared Survey Explorer (WISE)-selected AGNs are strongly concentrated in lower-mass regions and form two distinct clumps: one associated with bluer, starburst-like systems and the other with redder galaxies showing spectral features more typical of AGNs. This separation may help disentangle true AGN hosts from starburst contaminants in WISE-selected samples. Additionally, AGNs selected via various diagnostics tend to avoid regions of strong star formation, while a subset of lower-mass AGNs occupy SOM regions indicative of high AGN luminosity relative to their stellar content. Our results demonstrate the utility of manifold learning in refining AGN selection in the low-mass regime.

Keywords: AGN host galaxies, Black holes, Dwarf galaxies, Astronomy data analysis, Active galactic nuclei, Galaxy evolution, Galaxy spectroscopy, Astronomy data visualization
Genesis of a Confined X6.4 Flare in a Quadrupolar Magnetic Configuration. Both eruptive and confined flares—those having and lacking, respectively, an associated large-scale coronal mass ejection—are frequently observed in solar active regions (ARs). The physical mechanisms controlling the nature of these flares are poorly understood, requiring a detailed investigation of both the magnetic environment and the dynamic flare production process within the source region. Here we study a confined X6.4 flare with a failed filament eruption in AR 13590, observed by the SDO spacecraft on 2024 February 22. AR 13590 exhibited a quadrupolar magnetic configuration consisting of one central and two side arcades of low-lying loops, overlain by a fourth arcade of high-lying loops. A potential-field extrapolation contains a low-altitude null point at a height of approximately 5 Mm. This is a classic magnetic-breakout topology, except that the rising filament lay under one of the side arcades. The confined flare generated four ribbons located in all four of the major polarities, and proceeded in two phases, characterized by two successive stages of ribbon brightenings accompanied by forward and then reverse motion of the brightenings along the interior ribbons. We propose that the two phases represent breakout reconnection in the null region, which removed the flux ahead of the rising filament, followed by "anti-breakout" reconnection, corresponding to a reversed process as those flux systems evolved back toward the pre-eruption configuration. We discuss the implications of these observations for understanding how intense flares can occur without the expulsion of material from the solar corona.

Keywords: Solar flares, Solar corona, Solar extreme ultraviolet emission
Magnetohydrodynamic Tests of Galactic Synchrotron Depolarization. Synchrotron emission from cosmic-ray electrons accelerated in the Galactic magnetic field encodes information on the role of turbulence in the magnetized interstellar medium. Although synchrotron radiation is intrinsically highly polarized, the observed fractional polarization f = P/I is below 5% over most of the sky. Despite this marked depolarization, the remaining signal is highly aligned, with median scatter in polarization angle less than 15° within regions of 20° diameter on the sky. We use magnetohydrodynamic (MHD) simulations to determine the extent to which MHD turbulence can reproduce the observed pattern of substantial depolarization with minimal angular scatter. We evaluate both the synchrotron fractional polarization and polarization angle as projected through a suite of simulations with sonic Mach number  0.5&lt;MS&lt;6  and magnetic (Alfvén) Mach number  0.5&lt;MA&lt;4 . Simulations with a weakly magnetized plasma and strongly supersonic flow ( MA=2  with  4&lt;MS&lt;6 ) match the observed high-latitude sky. The fit improves when the angle between the observer and the seed magnetic field is 15°–30° from perpendicular, in agreement with models of the local inclination angle of the large-scale Galactic magnetic field. Additional improvement occurs if the estimated brightness of the unpolarized Galactic synchrotron emission is reduced, either by subtracting an unpolarized extragalactic component from the observed radio maps or by applying a steeper spectra index when scaling the unpolarized synchrotron intensity from 408 MHz to 30 GHz.

Keywords: Interstellar magnetic fields, Interstellar synchrotron emission, Radio continuum emission
Statistical Analysis of ∼100 Hz Whistler-mode Waves near the Moon Using ARTEMIS Observations. Utilizing 11 yr of Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun P1 and P2 observations from 2013 to 2023, we perform a comprehensive statistical analysis of ∼100 Hz whistler-mode waves near the Moon. The investigation focuses on waves in the unique lunar environment, characterized by the absence of a global magnetic field and the presence of localized crustal magnetic anomalies. We carefully investigate the spatial distribution, amplitude, and peak frequencies of these waves, including their dependence on solar wind speed (Vsw), dynamic pressure (Pdyn), and interplanetary magnetic field strength (Btot). The results show that the wave amplitudes are predominantly between 0.01 and 0.3 nT, with significant differences in the spatial distribution of the ∼100 Hz waves inside and outside the Earth's magnetosphere. Magnetic connection to the lunar surface significantly enhances the wave occurrence rate, while strong crustal magnetic fields suppress it. Wave amplitude exhibits a positive correlation with Pdyn, and peak frequency increases with Btot. These obtained distribution features and dependencies of lunar ∼100 Hz whistler-mode waves are valuable to improve the current understanding of wave generation mechanisms and the underlying contribution of wave–particle interactions in the lunar plasma environment.

Keywords: Solar wind, The Moon, Planetary magnetospheres
The Physical Properties of Four Double-lined Detached Eclipsing Binaries with Similar Components and Third Bodies from the LAMOST Medium-resolution Survey. The stellar model is still facing challenges in explaining the origin of low-mass stars and brown dwarfs. Double-lined detached eclipsing binaries with low-mass and similar components play an important astrophysical role in accurately deriving fundamental parameters, investigating stellar properties, and restricting theoretical stellar models of low-mass stars. Using high-precision light curves and Large Sky Area Multi-Object Fiber Spectroscopic Telescope spectra, we first obtained the fundamental parameters of the four detached binaries (NSVS 07453183, V644 Aur, V912 Per, and V1250 Tau). Except for V1250 Tau (qsp∼ 0.95), the mass ratios of the other three targets are almost equal to 1, which is consistent with the core fragmentation and dynamical capture theories of binary formation. The O − C curves of these systems based on current data exhibit cyclic variations, which is due to the light-travel time effect caused by the presence of a third body. Among them, the third body of V912 Per is likely to be a stellar black hole  (M3sini3=12.57M⊙) . The O − C diagram of NSVS 07453183 shows double-cycle oscillations, which means that it is perhaps a quadruple system. The third body of NSVS 07453183 is an M3-type main-sequence star based on third light analysis, and the fourth body maybe a brown dwarf. The obtained Hertzsprung─Russell diagram based on the Modules for Experiments in Stellar Astrophysics code suggested that the components of these four targets are main-sequence stars. These four targets will gradually form Algol-type binaries in the future, which are important systems for studying the reversal of the mass ratio.

Keywords: Multiple stars, Fundamental parameters of stars, Light curves, Eclipsing binary stars, Radial velocity, Stellar evolution
Possible First Detection of Gyroresonance Emission from a Coronal Mass Ejection in the Middle Corona. Routine measurements of the magnetic field of coronal mass ejections (CMEs) have been a key challenge in solar physics. Making such measurements is important both from a space weather perspective and for understanding the detailed evolution of the CME. In spite of significant efforts and multiple proposed methods, achieving this goal has not been possible to date. Here we report the first possible detection of gyroresonance emission from a CME. Assuming that the emission is happening at the third harmonic, we estimate that the magnetic field strength ranges from 7.9 to 5.6 G between 4.9 and 7.5 R⊙. We also demonstrate that this high magnetic field is not the average magnetic field inside the CME, but most probably is related to small magnetic islands, which are also being observed more frequently with the availability of high-resolution and high-quality white-light images.

Keywords: Solar magnetic fields, Solar coronal mass ejections, Solar radio emission, Active sun
Eclipsing Millisecond Pulsars with He Star Companions. Eclipsing millisecond pulsars (MSPs) are a type of pulsar binaries with close orbits (≲1.0 day). They are important objects for studying the accretion history of neutron stars (NSs), pulsar winds, and the origin of isolated MSPs, etc. Recently, a new eclipsing MSP, PSR J1928+1815, was discovered by the Five-hundred-meter Aperture Spherical radio Telescope. It is the first known pulsar with a He star companion, as suggested in Yang et al. The system features a short orbital period of ∼0.15 days and a relatively massive companion ≳1.0 M⊙. However, the origin of PSR J1928+1815 remains highly uncertain. In this paper, we investigated the formation of the new subclass of eclipsing MSPs containing (evolved) He star companions through the NS + He star channel. We found that if an NS binary undergoes subsequent mass-transfer phases following Case BA or Case BB, it may appear as an eclipsing MSP during the detached phase. Additionally, we obtained the initial parameter space for producing eclipsing MSPs with He star companions. Using the binary population synthesis approach, we estimated their birth rate to be ∼2.1─4.7 × 10−4 yr−1, corresponding to a total number of ∼220 systems in the Galaxy. Moreover, we concluded that PSR J1928+1815 may originate from the evolution of an NS + He star system with an initial orbital period of ∼0.1 days, which can undergo the Case BB mass transfer.

Keywords: Close binary stars, X-ray binary stars, Millisecond pulsars