Sazuna/UAT_keywords huggingface dataset:
Dual Perspectives on GX 17+2: A Simultaneous NICER and NuSTAR Study. We performed the first simultaneous NICER and NuSTAR spectral and timing study of the Sco-like Z source GX 17+2. The source traced the full Z track during four observations. We detect signatures of relativistic reflection in the broadband spectra and report results using a reflection framework. The disk is relatively close to the innermost stable circular orbit (∼1RISCO─4RISCO), which agrees with previous studies of GX 17+2, but the location of the inner disk is farther out in the horizontal branch (HB) and moves inward toward the flaring branch (FB). We find the FB to be the point of closest approach of the disk to the neutron star. We qualitatively conclude that the evolution of the source along the hardness intensity diagram (HID) is that of a relatively truncated disk in the HB (∼4RISCO) that approaches the neutron star as it goes along the HID toward the normal branch (NB), soft apex (SA), and finally the FB. We attribute the source evolution along the Z track to varying mass accretion rate and disk instabilities. The rms variability increases from the NB toward the SA and then drops to a constant along the FB, indicating that the observed variability likely originates from the disk/boundary layer rather than the corona.

Keywords: Low-mass x-ray binary stars
Characterizing TESS-identified Quadruple- and Higher-order Eclipsing Binaries. I. Speckle Imaging with DSSI and HRCam. NASA's TESS mission has unveiled a plethora of eclipsing binaries (EBs), among them hundreds of triples and higher-order, hierarchical systems. These complex targets require follow-up observations to enable full characterization of system architectures and identify the most compact multiples expected to undergo the most dramatic dynamical evolution. We report first results from a long-term effort to perform such follow-up, focusing here on multiband speckle imaging of a majority (57) of the sample of 97 quadruple- and higher-order eclipsing binaries (Q+EBs) identified via TESS light curves by V. B. Kostov et al. Diffraction-limited imaging with the Differential Speckle Survey Instrument on the Astrophysical Research Consortium 3.5 m telescope and HRCam on the Southern Astrophysical Research 4.1 m telescope reveals nearly 60% of the 57 to resolve into two sources separated by ≥0 .″ 03. For these partly resolved systems, we report derived characteristics (e.g., relative position angle, angular separation, and magnitude differences in multiple passbands) from the speckle imaging. We find those Q+EBs partly resolved with 4 m class telescopes to have significantly inflated Gaia parallax errors and large Gaia renormalized unit weight errors, particularly for systems with separations comparable to Gaia's resolution limit (∼0 .″ 6). For unresolved systems we report upper limits on angular and linear projected separations. We find two partly resolved Q+EBs with wide linear separations having eclipse timing variations that are therefore candidates of higher-than-quadruple multiplicity. Finally, we demonstrate how speckle imaging of resolved Q+EBs during an eclipse can clarify which speckle-resolved Q+EB subsystem is associated with a particular set of TESS eclipses.

Keywords: Multiple stars, Binary stars, Light curves, Stellar dynamics, Photometry, Speckle interferometry, Eclipsing binary stars
The Draco Dwarf Spheroidal Galaxy in the First Year of Dark Energy Spectroscopic Instrument Data. We investigate the spatial distribution, kinematics, and metallicity of stars in the Draco dwarf spheroidal galaxy using data from the Dark Energy Spectroscopic Instrument (DESI). We identify 155 high-probability members of Draco using line-of-sight velocity and metallicity information derived from DESI spectroscopy along with Gaia Data Release 3 proper motions. We find a mean line-of-sight velocity of −290.62 ± 0.80 km s−1 with dispersion =  9.57−0.62+0.66  km s−1 and mean metallicity [Fe/H] = −2.10 ± 0.04, consistent with previous results. We also find that Draco has a steep metallicity gradient within the half-light radius, and a metallicity gradient that flattens beyond the half-light radius. We identify eight high-probability members outside the King tidal radius, four of which we identify for the first time. These extratidal stars are not preferentially aligned along the orbit of Draco. We compute an average surface brightness of 34.02 mag  arcsec−2  within an elliptical annulus from the King tidal radius of 48 .' 1─81'.

Keywords: Draco dwarf galaxy, Local Group, Dwarf galaxies, Galaxy evolution
Hybrid Strategy for Coordinated Interstellar Signaling: Linking the Galactic Center and Extragalactic Bursts. The search for extraterrestrial intelligence (SETI) is largely limited by the vastness of the signaling parameter space. The concurrent signaling scheme offers a framework in which civilizations can coordinate their transmission and reception by referring to a common astrophysical event. Building on this idea, I propose a hybrid strategy that combines the Galactic center as a spatial reference with an extragalactic burst as a temporal marker. If such a scheme is indeed employed, the sky area to be surveyed in SETI could be reduced by more than 2 orders of magnitude, based solely on existing astronomical data. I examine records of three types of extragalactic bursts (supernovae, neutron star mergers, and gamma-ray bursts, GRBs) to identify suitable temporal markers. Among them, GRB 221009A is particularly notable due to its high fluence and favorable sky location.

Keywords: Search for extraterrestrial intelligence, Astrobiology
Impact of Multimessenger Spectral Modeling on Blazar─Neutrino Associations. Blazars are interesting source candidates for astrophysical neutrino emission. Multimessenger leptohadronic models based on proton─photon (pγ) interactions result in predictions for the neutrino spectra ("pγ spectra"), which are typically strongly peaked at PeV energies. In contrast, statistical analyses looking to associate blazars and high-energy neutrinos often assume a power-law spectral shape, putting the emphasis at lower energies. We aim to examine the impact of such spectral modeling assumptions on the associations of neutrinos with blazars. We use hierarchical_nu, a Bayesian framework for point-source searches, and incorporate the theoretical predictions for neutrino spectra through a dedicated spectral model and priors on the relevant parameters. Our spectral model is based on recent predictions for a selection of intermediate and high synchrotron peaked blazars that have been found to be spatially close to high-energy events detected by IceCube. We apply our model to the 10 yr of publicly available muon track IceCube data aimed at point-source searches, focusing on the Northern Hemisphere. Out of 29 source candidates, we find five sources, including TXS 0506+056, that have an association probability Passoc &gt; 0.5 to at least one event. The pγ spectra typically lead to a lower overall number of associated events compared to the power-law case, but retain or even enhance strong associations to high-energy events. Our results demonstrate that including more information from theoretical predictions can allow for more interpretable source─neutrino connections.

Keywords: Bayesian statistics, High energy astrophysics, Neutrino astronomy, Astrostatistics, Hierarchical models, Astronomical methods
Diffusion Coefficients of WIND/STICS Protons from Diffusive Shock Acceleration with Finite Escape Boundaries. Heliospheric suprathermal ions include inner-source pickup ions, cometary ions, solar energetic particles, and suprathermal tail particles. Despite exhaustive observation and formalisms, their role in interplanetary shock acceleration has yet to be ascertained. Their role becomes ambiguous with observed departures from idealized, one-dimensional diffusive shock acceleration (DSA) theory, comprising an infinitesimally thin shock with escape at infinity. Applying a spatial free-escape boundary (FEB), a one-dimensional configuration is retained, yet the ion velocity distribution becomes expressible as a function of the spatial diffusion coefficient. The coefficient and its energy dependence serve to characterize magnetic irregularities, signatures from shock obliquity, and acceleration scales. Thus, study of proton diffusion coefficients in interplanetary shocks may elucidate the relative prevalence of DSA and more microscopic processes, and the applicability of frameworks such as quasilinear theory (QLT). Here, proton velocity distribution functions (VDFs) from the WIND Suprathermal Ion Composition Spectrometer (WIND/STICS) are studied, with energies per charge of 6.2─223.1 keV/e, for two shocks having quasi-parallel and quasi-perpendicular orientations. The VDFs are then averaged over the STICS field of view and expressed as a function of distance from the shock, and fit to the exponential in position from convection/diffusion with the FEB. The energy dependence of diffusion coefficients, and the relative importance of acceleration mechanisms, are then examined. The coefficients are power laws in proton energy, more proper to QLT than to DSA under classical scattering, although behavior is variously described by both regimes. The quasi-perpendicular shock yields a negative power-law slope downstream, an effect suggesting both convergence of mechanisms and the model's shortcomings.

Keywords: Interplanetary shocks
Accretion Flow Properties of Swift J1727.8─1613 during Its Rising Phase of the Discovery Outburst: Estimation of Mass from Spectrotemporal Study. The rising phase of the 2023─24 outburst of the recently discovered bright transient black hole candidate Swift J1727.8─1613 was monitored by Insight-HXMT. We study the evolution of hard-band (4─150 keV) and soft-band (2─4 keV) photon count rates, the hardness ratio (HR), quasiperiodic oscillation (QPO) frequencies, and spectral features using daily observations from the HXMT/LE, ME, and HE instruments between 2023 August 25 and October 5. The QPO frequency is found to be strongly correlated with the soft-band X-ray count rates and spectral photon indices. In contrast, a strong anticorrelation is observed between HR and QPO frequency, as well as between HR and photon index. Based on the evolution of the temporal and spectral properties, the rising phase of the outburst is subdivided into six parts. The evolution of the QPOs in parts 1─5 is fitted with the propagating oscillatory shock solution to understand the nature of the evolution from a physical perspective. An inward-propagating shock with weakening strength (except in part 4) is observed during the period of our study. The probable mass of the source is estimated to be 13.5 ± 1.9 M⊙ using the QPO frequency (ν)─photon index (Γ) scaling method.

Keywords: Accretion, Black hole physics, X-ray binary stars, X-ray transient sources, Shocks
Self-Consistent Heating of the Magnetically Closed Solar Corona: Generation of Nanoflares, Thermodynamic Response of the Plasma and Observational Signatures. The energy that heats the magnetically closed solar corona originates in the complex motions of the massive photosphere. Turbulent photospheric convection slowly displaces the footpoints of coronal field lines, causing them to become twisted and tangled. Magnetic stresses gradually build until reaching a breaking point when the field reconnects and releases a sudden burst of energy. We simulate this basic picture of nanoflares using a high-fidelity, three-dimensional, multistranded magnetohydrodynamic simulation that starts with a fully stratified atmosphere. This simulation includes the effects of field-aligned thermal conduction and optically thin radiation and uses the state-of-the-art Transition Region Adaptive Conduction (TRAC) method to capture the response of the plasma to the nanoflare heating. We find that our physical model supports a unified explanation for both the diffuse emission observed in active regions and the bright coronal loops. Specifically, our results suggest that the diffuse emission originates from spatially and temporally uncorrelated nanoflares, whereas coherent clusters of nanoflares—nanoflare storms—are responsible for the formation of bright coronal loops. Quantitative comparisons between the simulated emission and observed characteristics of coronal loops show that key observed properties—such as loop widths, lifetimes, and cross sections—are reasonably well reproduced by the model. The idea that avalanche spread naturally leads to circular cross sections in coronal loops is strongly supported. Our results also suggest that phase differences in heating and cooling events across neighboring magnetic flux strands are a plausible explanation for the anomalous cross-field motions of coronal loops that were recently reported in high-resolution observations.

Keywords: Magnetohydrodynamics, Solar magnetic reconnection, Solar extreme ultraviolet emission, Solar coronal loops, Solar coronal heating, Solar active regions, Solar magnetic fields, Solar corona
Far-ultraviolet Emission Line Investigation of Flares on AU Mic. The role of nonthermal proton energy transportation during solar and stellar flares is largely unknown; a better understanding of this physical process will allow us to rectify longstanding deficiencies in flare models. One way to detect the presence of nonthermal protons during flares is through the Orrall─Zirker (OZ) effect, proposed by F. Q. Orrall &amp; J. B. Zirker, whereby an enhanced red wing appears in hydrogen emission lines (e.g., Lyman-α at 1215.67 Å). We analyze archival Hubble Space Telescope/Cosmic Origins Spectrograph G130M (1060─1360 Å) observations of the young M dwarf AU Microscopii (AU Mic) to search for evidence of the OZ effect during the impulsive phase of six stellar flares with  Eflare≍1030−31  erg. While we found nondetections of the OZ effect, we note there is a pronounced blue enhancement in several C II and C III emission lines during one of the high-energy flares. We propose that either filament eruptions or chromospheric evaporation could be the mechanism driving this observed blue enhancement. We compare the far-ultraviolet (FUV) spectra to one-dimensional radiative-hydrodynamic stellar flare models, which are unable to reproduce the blue enhancement and broadening in these cool flare lines. By completing a line-by-line analysis of the FUV spectrum of AU Mic, we provide further constraints on the physical mechanisms producing stellar flares on M dwarfs.

Keywords: Stellar chromospheres, Ultraviolet spectroscopy, Stellar activity, Stellar physics, Stellar flares
Luminous Late-time Radio Emission from Supernovae Interacting with Circumbinary Material. Numerous core-collapse supernovae (CCSNe) exhibit signatures of interaction with circumstellar material (CSM). Bright radio emission years after the supernova (SN) is one such indication of dense CSM at large distances from the star, which may be generated via binary interactions. In this work, we use forward modeling to study the radio emission produced by the interaction between the SN ejecta and CSM formed by nonconservative stable mass transfer from stripped-envelope stars in short-period binaries. The donors are among the likely progenitors of hydrogen-poor CCSNe that significantly expand 103─104 yr before core collapse, with companions that best represent low-mass compact objects. We identify that nonconservative stable mass transfer from lower-mass stripped stars can create a detached shell-like CSM, whereas for our higher-mass stars, the CSM is wind-like. In our models, mass-transfer rates of ∼10−4 M⊙ yr−1 lead to dense CSM extending to ∼1018 cm. The predicted radio emission is luminous at late times, reaching Lν ∼ 1026─1029 erg s−1Hz−1 at years to decades after core collapse, which is as bright as late-time radio emission observed for a sample of hydrogen-poor SNe. However, the light curves of events with early-time data show more complex behavior in the weeks to months after core collapse. We qualitatively demonstrate that similar early-time emission can manifest for a CSM that is accelerated to speeds of ∼103 km s−1 upon ejection, as well as for different viewing angles in the case of an asymmetric CSM distribution.

Keywords: Binary stars, High energy astrophysics, Core-collapse supernovae, Roche lobe overflow, Radio transient sources
Cosmic-ray Perpendicular Superdiffusion and Parallel Mirror Diffusion in a Partially Ionized and Turbulent Medium. Understanding cosmic-ray (CR) diffusion in a partially ionized medium is both crucial and challenging. In this study, we investigate CR perpendicular superdiffusion and parallel transport in turbulent, partially ionized media using high-resolution 3D two-fluid simulations that treat ions and neutrals separately. We examine the influence of neutral-ion decoupling and the associated damping of turbulence on CR propagation in both transonic and supersonic conditions. Our simulations demonstrate that neutral-ion decoupling significantly damps velocity and magnetic field fluctuations at small scales, producing spectral slopes steeper than those of Kolmogorov and Burgers scaling. In supersonic turbulence, large-scale shock motion is not subject to damping and generates small-scale density enhancements. Moreover, the damping of magnetic field fluctuations substantially decreases pitch-angle scattering, which, however, only slightly affects the CR parallel mean free path λ∥, due to the nonresonant mirror interactions of CRs. In the direction perpendicular to the mean magnetic field, we identify two regimes of the perpendicular superdiffusion of CRs: a diffusive regime (λ∥ &lt; Linj, where Linj is the turbulence injection scale) with perpendicular separation of CR proportional to t3/4 and a ballistic regime (λ∥ &gt; Linj) with perpendicular separation scaling as t3/2. At initially large pitch angles, the effects of magnetic mirroring—naturally arising in magnetohydrodynamic turbulence—become significant, enhancing the confinement of CRs and resulting in λ∥ &lt; Linj, despite the damping effect. These results imply that large-pitch-angle CRs can be well confined in the cold interstellar medium, such as molecular clouds.

Keywords: Magnetohydrodynamics, Plasma astrophysics, Interstellar medium, Cosmic rays
oMEGACat. VII. Tracing Interstellar and Intracluster Medium of ω Centauri Using Sodium Absorptions. We investigate the foreground interstellar medium along the line of sight and intracluster medium of ω Centauri (ω Cen) by measuring the equivalent width of Na I D absorptions from MUSE observations. The large line-of-sight velocity difference between ω Cen and the foreground enables us to separate Na I D absorption contributed from atomic gas in the interstellar and intracluster medium. We find that small-scale substructures in the foreground Na I D distribution correlate with differential reddening derived from photometric methods. Using an empirical Na I D equivalent width-reddening relation, we determine an average reddening of E(B − V) = 0.153 ± 0.003 mag within the half-light radius of ω Cen. However, the Na I D-inferred differential reddening is significantly larger than photometric estimates. This is likely due to scatter in the Na I D-reddening relation. We find no evidence for intracluster atomic gas from spectra of horizontal branch stars, as there is no significant Na I D absorption at ω Cen's systemic velocity. Given this nondetection, we place the strongest upper limit to date on the intracluster atomic gas column density in ω Cen of ≲2.17 × 1018 cm−2. We also estimate the ionized gas density from pulsar dispersion measure variations, which exceed the atomic gas limit by ∼50 times. Nevertheless, the strong correlation between dispersion measure and foreground Na I D suggests that much or all of this ionized gas resides in the foreground. Given ongoing mass loss from bright giant stars, our findings imply that the intracluster gas accumulation timescale is short and gas removal in the cluster is likely not tied to stripping as ω Cen passes through the galactic disk.

Keywords: Globular star clusters, Interstellar line absorption, Galaxy nuclei, Interstellar medium, Star clusters
microJAX: A Differentiable Framework for Microlensing Modeling with GPU-accelerated Image-centered Ray Shooting. We introduce microJAX, the first fully differentiable implementation of the image-centered ray shooting algorithm for gravitational microlensing. Built on JAX and its XLA just-in-time compiler, microJAX exploits GPU parallelism while providing exact gradients through automatic differentiation. The current release supports binary- and triple-lens geometries, including limb-darkened extended-source effects, and delivers magnifications that remain differentiable for all model parameters. Benchmarks show that microJAX matches the accuracy of established packages and attains up to a factor of ∼5─6 speedup in the small-source, limb-darkened regime on an NVIDIA A100 GPU. Since the model is fully differentiable, it integrates seamlessly with probabilistic programming frameworks, enabling scalable Hamiltonian Monte Carlo and variational inference workflows. Although the present work focuses on standard microlensing magnification models, the modular architecture is designed to support upcoming implementations of microlensing higher-order effects, while remaining compatible with external likelihood frameworks that incorporate advanced noise models. microJAX thus provides a robust foundation for precise and large-scale surveys anticipated in the coming decade, including the Nancy Grace Roman Space Telescope, where scalable, physically self-consistent inference will be essential for maximizing scientific return.

Keywords: Gravitational microlensing, Triple lens microlensing, Binary lens microlensing
The Role of Spiral Arms in Galaxies. II. Similarities amid Diversity. The role of spiral arms in galaxies—whether they enhance star formation efficiency or primarily act as material gatherers—remains an open question. Observational studies have yielded ambiguous results, in part due to the choice of star formation rate (SFR) tracers and their inherent limitations. These limitations are addressed here by applying multiwavelength spectral energy distribution fitting to individual arm and interarm regions. We expand on our previous study of two galaxies to include six diverse galaxies, spanning over an order of magnitude in total stellar mass and factors of several in total SFR, for which spiral arms have been mapped. We find that the specific star formation rate (sSFR = SFR/Mstar) can be used as a proxy for the star formation efficiency (SFE = SFR/Mgas), since the two quantities are directly proportional to each other in our regions. In our analysis of both tracers (sSFR and SFE) no significant difference is found the between arm and interarm regions, except for one galaxy (NGC 1097), supporting the gatherer scenario.

Keywords: Spiral arms, Star formation, Spectral energy distribution, Spiral galaxies