Sazuna/UAT_keywords huggingface dataset:
OGLE-2011-BLG-0462: An Isolated Stellar-mass Black Hole Confirmed Using New HST Astrometry and Updated Photometry. The long-duration Galactic-bulge microlensing event OGLE-2011-BLG-0462 produced relativistic astrometric deflections of the source star, which we measured using Hubble Space Telescope (HST) observations taken at eight epochs over ∼6 yr. Analysis of the microlensing light curve and astrometry led our group (followed by other independent groups) to conclude that the lens is an isolated stellar-mass black hole (BH)—the first and only one unambiguously discovered to date. There have now been three additional epochs of HST observations, increasing the astrometric time baseline to 11 yr. Additionally, the ground-based OGLE data have been updated. We have reanalyzed the data, including the new HST astrometry, and photometry obtained with 16 different telescopes. The source lies only   from a bright neighbor, making it crucial to perform precise subtraction of its point-spread function (PSF) in the astrometric measurements of the source. Moreover, we show that it is essential to perform a separate PSF subtraction for each individual HST frame as part of the reductions. Our final solution yields a lens mass of 7.15 ± 0.83 M⊙. Combined with the lack of detected light from the lens at late HST epochs, the BH nature of the lens is conclusively verified. The BH lies at a distance of 1.52 ± 0.15 kpc, and it is moving with a space velocity of 51.1 ± 7.5 km s‑1 relative to the stars in the neighborhood. We compare our results with those of other studies and discuss reasons for the differences. We also searched for binary companions of the BH at a range of separations, but found no evidence for any.

Keywords: Space astrometry, Black holes
Magnetically Assisted Vorticity Production in Decaying Acoustic Turbulence. We study vorticity production in isothermal, subsonic, acoustic (nonvortical), and decaying turbulence due to the presence of magnetic fields. Using three-dimensional numerical simulations, we find that the resulting kinetic energy cascade follows the ordinary Kolmogorov phenomenology involving a constant spectral energy flux. The nondimensional prefactor for acoustic turbulence is larger than the standard Kolmogorov constant due to the inefficient dissipation of kinetic energy. We also find that the Lorentz force can drive vortical motions even when the initial field is uniform by converting a fraction of the acoustic energy into vortical energy. This conversion is shown to be quadratic in the magnetic field strength and linear in the acoustic flow speed. By contrast, the direct production of vortical motions by a non-force-free magnetic field is linear in the field strength. Our results suggest that magnetic fields play a crucial role in vorticity production in cosmological flows, particularly in scenarios where significant acoustic turbulence is prevalent. We also discuss the implications of our findings for the early Universe, where magnetic fields may convert acoustic turbulence generated during cosmological phase transitions into vortical turbulence.

Keywords: Magnetic fields
Chaotic Behavior of Trapped Cosmic Rays. Recent experimental results on the arrival direction of high-energy cosmic rays have motivated studies to understand their propagating environment. The observed anisotropy is shaped by interstellar and local magnetic fields. In coherent magnetic structures, such as the heliosphere, or due to magnetohydrodynamic turbulence, magnetic mirroring can temporarily trap particles, leading to chaotic behavior. In this work, we develop a new method to characterize cosmic rays' chaotic behavior in magnetic systems using finite-time Lyapunov exponents. This quantity determines the degree of chaos and adapts to transitory behavior. We study particle trajectories in an axial-symmetric magnetic bottle to highlight mirroring effects. By introducing time-dependent magnetic perturbations, we study how temporal variations affect chaotic behavior. We tailor our model to the heliosphere; however, it can represent diverse magnetic configurations exhibiting mirroring phenomena. Our results have three key implications. (1) Theoretical: We find a correlation between the finite-time Lyapunov exponent and the particle escape time from the system, which follows a power law that persists even under additional perturbations. This power law may reveal intrinsic system characteristics, offering insight into propagation dynamics beyond simple diffusion. (2) Simulation: Chaotic effects play a role in cosmic-ray simulations and can influence the resulting anisotropy maps. (3) Observational: Arrival maps display areas where the chaotic properties vary significantly; these changes can be the basis for time variability in the anisotropy maps. This work lays the framework for studying the effects of magnetic mirroring of cosmic rays within the heliosphere and the role of temporal variability in the observed anisotropy.

Keywords: High energy astrophysics, Heliosphere, Solar wind, Cosmic ray astronomy, Galactic cosmic rays, Magnetic fields, Cosmic rays
Kinetic-hybrid Simulations of Counterpropagating Ion Cyclotron Waves and Proton Scattering in the Near-Sun Solar Wind. Ion cyclotron waves (ICWs) are prevalent in the near-Sun solar wind and play a significant role in the nonadiabatic heating of plasma. Recent observations from the Parker Solar Probe have revealed the simultaneous presence of antisunward and sunward ICWs in the vicinity of the Alfvén surface. However, single-satellite observations cannot effectively trace the generation and evolution of these observed waves. To address this limitation, we employ kinetic-hybrid simulations to replicate the generation and evolution of counterpropagating ICWs under typical plasma conditions in the near-Sun solar wind. Following the linear growth phase, the simulated waves exhibit amplitude and polarization characteristics that closely match the observations. Additionally, our simulation illustrates proton scattering induced by the counterpropagating waves. These results underscore the significance of locally generated ICWs in influencing solar wind ion dynamics.

Keywords: Space plasmas, Solar wind, Plasma physics
Comparison of Coronal Hole and Quiet-Sun Chromosphere Using IRIS Mg II h and k Observations of Polar Off-limb Regions. Solar quiet regions are divided into coronal hole regions (CH) and quiet-Sun regions (QS). The global magnetic field in CH is considered open to interplanetary space, while that in QS is closed. To constrain the solar atmosphere and solar wind model, we statistically compared CH and QS in the chromosphere by quantitatively analyzing all available high-resolution spectral data sets of polar off-limb regions taken from the entire catalog of the Interface Region Imaging Spectrograph (IRIS) satellite. We extracted the characteristic quantities from the Mg II h and k line profiles and compared the dependence of those quantities on the height from the photospheric limb. The main findings are as follows. First, the integrated intensities in the Mg II k line show a steeper decrease with height in QS while they remain bright at higher altitudes in CH. Second, the unsigned line-of-sight velocities in the Mg II k line generally increase with height in both regions, although the unsigned velocities increase with height more strongly in QS than in CH. Third, the Mg II k line widths increase just above the limb and then decrease with height in both CH and QS, but are overall larger for CH than for QS, especially at the lower altitudes. Finally, we found the ratio of the Mg II k and h lines to show a two-step increase with height in both regions. The results suggest the spicules are higher in CH, and the CH chromosphere exhibits faster motions than the QS.

Keywords: Solar spicules, Solar ultraviolet emission, Quiet solar chromosphere, Spectroscopy
Multiwavelength Study of a Hyperluminous X-Ray Source near NGC 6099: A Strong IMBH Candidate. We report on the intriguing properties of a variable X-ray source projected at the outskirts of the elliptical galaxy NGC 6099 (d ≈ 139 Mpc). If truly located near NGC 6099, this is a hyperluminous X-ray source that reached an X-ray luminosity LX ≈ a few times 1042 erg s‑1 in 2012 February (XMM-Newton data), about 50–100 times brighter than in 2009 May (Chandra) and 2023 August (XMM-Newton). The X-ray spectrum was soft at all three epochs, with a thermal component at kT ≈ 0.2 keV and a power-law photon index &gt;3. Such properties make it a strong candidate for an intermediate-mass black hole (IMBH). We also discovered a point-like, blue optical counterpart (mg,Vega ≈ 24.7 mag, Mg,Vega ≈ ‑11.2 mag), from images taken by the Canada–France–Hawaii Telescope and later confirmed with Hubble Space Telescope observations. The optical continuum can be modeled as stellar emission from a compact star cluster or an X-ray-irradiated accretion disk, consistent with the IMBH scenario. We discuss alternative explanations for the nature of this system. A possible scenario is tidal stripping of an orbiting star, with repeated X-ray outbursts every few years. An alternative possibility is that the thermal X-ray emission seen in 2009 was from shocked gas in the self-intersecting tidal stream during the rising phase of a tidal disruption event, while the 2012 and 2023 emissions were from the fully formed accretion disk.

Keywords: Accretion, Intermediate-mass black holes, Ultraluminous x-ray sources, X-ray binary stars
JWST-IPA: Chemical Inventory and Spatial Mapping of Ices in the Protostar HOPS 370—Evidence for an Opacity Hole and Thermal Processing of Ices. The composition of protoplanetary disks, and hence the initial conditions of planet formation, may be strongly influenced by the infall and thermal processing of material during the protostellar phase. The composition of dust and ice in protostellar envelopes, shaped by energetic processes driven by the protostar, serves as the fundamental building material for planets and complex organic molecules. As part of the JWST General Observers program, "Investigating Protostellar Accretion," we observed an intermediate-mass protostar HOPS 370 (OMC2-FIR3) using NIRSpec integral field unit and Mid-Infrared Instrument medium-resolution spectroscopy. This study presents the gas and ice phase chemical inventory revealed with the JWST in the spectral range of ∼2.9–28 μm and explores the spatial variation of volatile ice species in the protostellar envelope. We find evidence for the thermal processing of ice species throughout the inner envelope. We present the first high-spatial resolution (∼80 au) maps of key volatile ice species H2O, CO2, 13CO2, CO, and OCN‑, which reveal a highly structured and inhomogeneous density distribution of the protostellar envelope, with a deficiency of ice column density that coincides with the jet/outflow shocked knots. Further, we observe high relative crystallinity of H2O ice around the shocked knot seen in the H2 and OH wind/outflow, which can be explained by a lack of outer colder material in the envelope along the line of sight due to the irregular structure of the envelope. These observations show clear evidence of thermal processing of the ices in the inner envelope, close to the outflow cavity walls, heated by the luminous protostar.

Keywords: Stellar jets, Astrochemistry, James Webb Space Telescope, Star formation, Protostars
Inferring Jet Structure and Viewing Angles of Gamma-Ray Burst Jets from Early Rising Optical Afterglows. We present the first systematic investigation of off-axis jets in gamma-ray bursts based on rising optical afterglows. As a pilot study, we selected eight well-observed bright optical afterglows and performed a Bayesian inference using two different jet models: a Gaussian-structured jet and a homogeneous top-hat jet. Assuming an adiabatic evolution of the fireball through a constant-density ambient medium, we derived the key afterglow parameters: viewing angle (θv), jet opening angle (θj for top-hat jets) or characteristic angle (θc for Gaussian jets), ambient medium number density n0, and ϵB measuring the downstream magnetic field strength. The inferred viewing angles of the sample range from 0.4° to 9.7°. Our results identify delayed optical peaks (occurring hundreds to thousands of seconds postburst) and low luminosity as key signatures of misaligned jets, with slow rises to peak suggesting structured jets. We further observe a correlation between the rest-frame peak time and the degree of misalignment in optical light curves. A larger sample size is required to confirm this.

Keywords: Gamma-ray bursts
Multiwavelength Evidence for Two New Candidate Transitional Millisecond Pulsars in the Subluminous Disk State: 4FGL J0639.1-8009 and 4FGL J1824.2+1231. We report the discovery of two new Galactic accreting compact objects consistent with the respective positions of the unassociated Fermi-LAT γ-ray sources 4FGL J0639.1-8009 and 4FGL J1824.2+1231. A combination of new and archival X-ray data from Chandra, XMM-Newton, Swift/XRT, and eROSITA reveals a variable X-ray source in each γ-ray error ellipse. Both candidate counterparts show power-law spectra with photon indices Γ ∼ 1.7–1.9. Optical follow-up photometry and spectroscopy show rapid high-amplitude variability unrelated to orbital motion and persistent accretion disk spectra for both objects. We demonstrate that the properties of these X-ray/optical sources are at odds with the known phenomenology of accreting white dwarfs, but are consistent with the observed properties of the subluminous disk state of transitional millisecond pulsars. This brings the census of confirmed or candidate transitional millisecond pulsars in the Galactic field to nine. We show this potentially represents ≲10% of the total population of transitional millisecond pulsars within 8 kpc.

Keywords: Compact binary stars, Millisecond pulsars
How Low Can Q Go?. Gravitational instability plays a substantial role in the evolution of galaxies. Various schemes to include it in galaxy evolution models exist, generally assuming that the Toomre Q parameter is self-regulated to Qcrit, the critical Q dividing stable from unstable conditions in a linear stability analysis. This assumption is in tension with observational estimates of Q that find values far below any plausible value of Qcrit. While the observations are subject to some uncertainty, this tension can more easily be relieved on the theoretical side by relaxing the common assumption that Q ≥ Qcrit. Based on observations of both z ∼ 2 disks and local face-on galaxies, we estimate the effect of gravitational instability necessary to balance out every other physical process that affects Q. In particular, we find that the disk's response to low Q values can be described by simple functions that depend only on Q. These response functions allow galaxies to maintain Q values below Qcrit in equilibrium over a wide range of parameters. Extremely low values of Q are predicted when the gas surface density is ≳103 M⊙ pc‑2, the rotation curve provides minimal shear, the orbital time becomes long, and/or when the gas is much more unstable than the stellar component. We suggest that these response functions should be used in place of the Q ≥ Qcrit ansatz.

Keywords: Galaxy disks, Galaxies, Gravitational instability, Disk galaxies
Simulation of Binary-single Interactions in AGN Disk. I. Gas-enhanced Binary Orbital Hardening. Stellar-mass binary black hole (BBH) mergers within the accretion disks of active galactic nuclei may contribute to gravitational wave (GW) events detected by ground-based GW detectors. In particular, the interaction between a BBH and a single stellar-mass black hole (sBH), known as the binary-single interaction (BSI) process, can potentially lead to GW events with detectable nonzero eccentricity. Previous studies of the BSI process, which neglected the effects of gas, showed that BSIs contribute non-negligibly to GW events in a coplanar disk environment. In this work, we conduct a series of two-dimensional hydrodynamical and N-body simulations to explore the BSI in a gas environment by coupling REBOUND with Athena++. We perform 360 simulation runs, spanning parameters in disk surface density Σ0 and impact parameter b. We find that the gas-induced energy dissipation within the three-body system becomes significant if the encounter velocity between the sBHs is sufficiently large (≫cs). Our simulation results indicate that approximately half of the end states of the BSI are changed by gas. Furthermore, at higher gas density, the number of close encounters during the BSI process will increase, and the end-state BBHs tend to be more compact. Consequently, the presence of gas may shorten the GW merger timescale for end-state BBHs and increase the three-body merger rate.

Keywords: Gravitational interaction, Hydrodynamical simulations, Active galactic nuclei, Gravitational waves
Triple Evolution Pathways to Black Hole Low-mass X-Ray Binaries: Insights from V404 Cygni. A recent discovery shows that V404 Cygni, a prototypical black hole low-mass X-ray binary (BH-LMXB) is a hierarchical triple: the BH and donor star are orbited by a 1.2 M⊙ tertiary at a distance of at least 3500 au. Motivated by this system, we evolve a grid of ∼50,000 triple star systems, spanning a broad range of initial orbits. Our calculations employ MESA stellar evolution models, using POSYDON, and self-consistently track the effects of eccentric Kozai–Lidov (EKL) oscillations, mass loss, tides, and BH natal kicks. In our simulations, the progenitors of V404 Cygni-like systems have initial outer separations of 1000–10,000 au and inner separations of ∼100 au, such that they avoid Roche lobe overflow most of the time. Later on, EKL oscillations drive the inner binary to high eccentricities until tides shrink the orbit and mass transfer begins. Notably, such systems only form in simulations with very weak black hole natal kicks (≲5 km s‑1) because stronger kicks unbind the tertiaries. Our simulations also predict a population of BH-LMXB triples that form via the classical common-envelope channel, when the BH progenitor does overflow its Roche lobe. The formation rate for this channel is also higher in triples than in isolated binaries because early EKL oscillations cause inner binaries with a wider range of initial separations to enter and survive a common envelope. Our calculations demonstrate that at least some stellar BHs form with extremely weak kicks, and that triple evolution is a significant formation channel for BH-LMXBs.

Keywords: Trinary stars, Binary stars, Black holes
Simultaneous Multiwavelength Observations of the Repeating Fast Radio Burst FRB 20190520B with Swift and FAST. Among several dozen known repeating fast radio bursts, those precisely localized offer the best opportunities to explore their multiwavelength counterparts, which are key to uncovering their origins. Here we report our X-ray, ultraviolet (UV), and optical observations with the Swift satellite of the repeating FRB 20190520B, in coordination with simultaneous radio observations with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Our aim was to detect potentially associated multiwavelength bursts and identify any persistent multiwavelength counterparts to the associated persistent radio source (PRS). While a total of 10 radio bursts were detected by FAST during the Swift observations, we detected no X-ray, UV, or optical bursts in accompany with the radio bursts. We obtained the energy upper limits (3σ) on any multwavelength bursts as follows: 5.03 × 1047 erg in the hard X-ray band (15–150 keV), 7.98 × 1045 erg in the soft X-ray band (0.3–10 keV), and 4.51 × 1044 erg in the U band (3465 Å), respectively. The energy ratio between soft X-ray (0.3–10 keV) and radio emission of the bursts is constrained as &lt;6 × 107, and the ratio between optical (U band) and radio as &lt;1.19 × 106. We detect no multiwavelength counterpart to the PRS. The 3σ luminosity upper limits are 1.04 × 1047 (15–150 keV), 8.81 × 1042 (0.3–10 keV), 9.26 × 1042 (UVW1), and 2.54 × 1042 erg s‑1 (U), respectively. We show that the PRS is much more radio-loud than representative pulsar wind nebulae, supernova remnants, extended jets of Galactic X-ray binaries, and ultraluminous X-ray sources, suggestive of boosted radio emission of the PRS.

Keywords: Transient sources, Radio transient sources
Neutron-capture Element Abundances of 491 Stars in Milky Way Dwarf Satellite Galaxies from Medium-resolution Spectra. The chemical compositions of evolved stars in Local Group dwarf spheroidal galaxies (dSphs) provide insight into the galaxy's past star formation and nucleosynthesis. Neutron-capture element abundances are especially interesting. In particular, s-process elements can provide a third chemical clock for resolving star formation histories in addition to core-collapse and Type Ia supernovae. Likewise, the primary sites of the r-process are still areas of extensive research. Until now, the number of stars with neutron-capture element abundances in dSphs has been limited by the need for stars bright enough for high-resolution spectroscopy. We present abundance measurements of the neutron-capture elements Sr, Y, Ba, and Eu with errors &lt;0.4 dex—as well as new measurements of Mg—in 491 stars in Sculptor, Fornax, Draco, Sextans, and Ursa Minor. The large number of stars in our sample is possible because we used medium-resolution spectra from the DEIMOS spectrograph, assembling the largest homogeneous set of neutron-capture abundances in dSphs to date. By utilizing the abundances of both s- and r-process elements, we find evidence of an s-process contribution at early times in Sculptor from our measurements of [Ba/Fe]. This is a potential signature of s-process nucleosynthesis in fast-rotating massive stars. By comparing our measurements of [Eu/Fe] with [Mg/Fe], we show the need for an r-process source that has a short delay time to enrich stars in the dSphs. Thus, neutron star mergers are likely not the sole source of r-process material in dSphs.

Keywords: Local Group, Nucleosynthesis, Galactic archaeology, Dwarf galaxies, R-process, Asymptotic giant branch stars, S-process
Behavior of the Lyα Damping Wings as a Function of Reionization Topology. The damping wing signatures in high-redshift quasars have proven instrumental in studying the epoch of reionization. With the upcoming Euclid mission set to discover many more quasars, it is crucial to explore what this new set of quasars might reveal not only about the reionization history, but also about its topology. The topology should influence the shape and variation of quasar-damping wing signals across sightlines. We use 21cmFAST to generate patchy reionization models in cosmological volumes with diverse astrophysical parameters for the ionizing sources. We examine the median and the sightline-to-sightline variation (ΔSW68) for an ensemble of damping wing signals. We find that the neutral fraction xH I, quasar lifetime tq, quasar host halo mass Mqso, and minimum dark-matter halo mass (that can support star formation)   significantly impact the median signal. Parameters tied to the reionization topology, like xH I and  , strongly affect ΔSW68, compared with tq. Our findings highlight that quasar damping wings are sensitive to  , a key variable linking reionization topology, history, and feedback processes. We also explore the convergence of damping wing signals and ionized bubble sizes with box size. We present a suite of models to assess the ability of future quasar samples to constrain astrophysical model parameters and the additional systematic uncertainty on the neutral fraction incurred when fixed to a single fiducial value.

Keywords: Reionization, Quasars, Intergalactic medium