Sazuna/UAT_keywords huggingface dataset:
JWST Reveals CO Ice, Concentrated CO<SUB>2</SUB> Deposits, and Evidence for Carbonates Potentially Sourced from Ariel's Interior. The Uranian moon Ariel exhibits a diversity of geologically young landforms, with a surface composition rich in CO2 ice. The origin of CO2 and other species, however, remains uncertain. We report observations of Ariel's leading and trailing hemispheres, collected with NIRSpec (2.87–5.10 μm) on the James Webb Space Telescope. These data shed new light on Ariel's spectral properties, revealing a double-lobed CO2 ice scattering peak centered near 4.20 and 4.25 μm, with the 4.25 μm lobe possibly representing the largest CO2 Fresnel peak yet observed in the solar system. A prominent 4.38 μm 13CO2 ice feature is also present, as is a 4.90 μm band that results from 12CO2 ice. The spectra reveal a 4.67 μm 12CO ice band and a broad 4.02 μm band that might result from carbonate minerals. The data confirm that features associated with CO2 and CO are notably stronger on Ariel's trailing hemisphere compared to its leading hemisphere. We compared the detected CO2 features to synthetic spectra of CO2 ice and mixtures of CO2 with CO, H2O, and amorphous carbon, finding that CO2 could be concentrated in deposits thicker than ∼10 mm on Ariel's trailing hemisphere. Comparison to laboratory data indicates that CO is likely mixed with CO2. The evidence for thick CO2 ice deposits and the possible presence of carbonates on both hemispheres suggests that some carbon oxides could be sourced from Ariel's interior, with their surface distributions modified by charged particle bombardment, sublimation, and seasonal migration of CO and CO2 from high to low latitudes.

Keywords: Uranian satellites, Surface processes, Ice spectroscopy, Surface composition, Carbon dioxide, James Webb Space Telescope, Surface ices
Discovery of an Extremely r-process-enhanced Thin-disk Star with [Eu/H] = +0.78. Highly r-process-enhanced (RPE) stars are rare and usually metal poor ([Fe/H] &lt; ‑1.0), and they mainly populate the Milky Way halo and dwarf galaxies. This study presents the discovery of a relatively bright (V = 12.72), highly RPE (r-II) star ([Eu/Fe] = +1.32, [Ba/Eu] = ‑0.95), LAMOST J020623.21+494127.9. This star was selected from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope medium-resolution (R ∼ 7500) spectroscopic survey; follow-up high-resolution (R ∼ 25,000) observations were conducted with the High Optical Resolution Spectrograph installed on the Gran Telescopio Canarias. The stellar parameters (T eff = 4130 K,  logg  = 1.52, [Fe/H] = ‑0.54, ξ = 1.80 km s‑1) have been inferred taking into account nonlocal thermodynamic equilibrium effects. The abundances of [Ce/Fe], [Pr/Fe], and [Nd/Fe] are +0.19, +0.65, and +0.64, respectively, relatively low compared to the Solar r-process pattern normalized to Eu. This star has a high metallicity ([Fe/H] = ‑0.54) compared to most other highly RPE stars and has the highest measured abundance ratio of Eu to H ([Eu/H] = +0.78). It is classified as a thin-disk star based on its kinematics and does not appear to belong to any known stream or dwarf galaxy.

Keywords: Fundamental parameters of stars, Stellar abundances, Chemically peculiar stars
Analyses of Johannes Kepler's Sunspot Drawings in 1607: A Revised Scenario for the Solar Cycles in the Early 17th Century. Telescopic sunspot observations began in 1610 and captured subsequent solar cycles. In combination with proxy reconstructions on an annual scale, these data sets indicate a gradual transition between regular solar cycles and the Maunder Minimum. The telescopic sunspot observations missed the beginning of the first telescopic solar cycle (Solar Cycle ‑13), leaving room for considerable uncertainty as to its temporal evolution. Before these early telescopic observations, however, Kepler made solar observations using camerae obscurae and recorded a sunspot group in three solar drawings in 1607. Here, we make use of Kepler's sunspot drawings and descriptive texts to identify his observational sites and time stamps. We have deprojected his sunspot drawings and compared the reported positions with our calculations of the inclination of the solar equator as seen from these sites at that time. These results locate the reported sunspot group near the solar equator eastward from the central meridian. This contrasts with telescopic sunspot drawings from the 1610s that show sunspot groups in the higher heliographic latitudes. Therefore, what Kepler saw was probably a sunspot group from Solar Cycle ‑14, rather than one from Solar Cycle ‑13. These records allow us to place the beginning of Solar Cycle ‑13 between 1607 and 1610. In comparison with the 14C-based solar-cycle reconstructions, our result supports regular solar-cycle durations around the 1610s, rather than any suggested extreme extensions of the solar-cycle duration(s) around the 1610s.

Keywords: Solar cycle, Sunspot groups, Sunspots, Maunder minimum, Solar-terrestrial interactions, Sunspot cycle
Cosmology from One Galaxy in a Void?. Understanding galaxy properties may be the key to unlocking some of the most intriguing mysteries of modern cosmology. Recent work relied on machine learning to extract cosmological constraints on Ωm using only one galaxy. But if this is true, how should we select the galaxy to use for cosmology inference? In this Letter, we consider selecting a galaxy that lies in cosmic voids, the underdense regions of the cosmic web, and compare the constraints obtained with the ones obtained when randomly selecting a galaxy in the whole sample. We use the IllustrisTNG galaxy catalog from the Cosmology and Astrophysics with MachinE Learning Simulations (CAMELS) project and the VIDE void finder to identify galaxies inside voids. We show that void galaxies provide stronger constraints on Ωm compared to randomly selected galaxies. This result suggests that the distinctive characteristics of void galaxies may provide a cleaner and more effective environment for extracting cosmological information.

Keywords: Cosmology, Voids, Galaxy properties, Astrostatistics
A Timing View of the Additional High-energy Spectral Component Discovered in the Black Hole Candidate Swift J1727.8-1613. We present an energy-dependent analysis for the type-C quasiperiodic oscillations (QPOs) observed in the black hole X-ray binary Swift J1727.8–1613 using Insight-HXMT observations. We find that the QPO fractional rms at energies above 40 keV is significantly higher than that below 20 keV. This is the first report of a high energy (HE) rms excess in the rms spectrum of a black hole X-ray binary. In the high energy band, an extra hard component is observed in addition to the standard thermal Comptonization component at a similar energy band. The value of the QPO HE rms excess is not only correlated with the disk parameters and the photon index of the standard Comptonization component but also exhibits a moderate positive correlation with the flux of the additional hard spectral component. No features in the QPO phase-lag spectra are seen corresponding to the additional hard component. We propose that the additional hard component in the spectrum may originate from jet emission and the associated QPO HE rms excess can be explained by the precession of the jet base.

Keywords: Low-mass x-ray binary stars, Accretion, Stellar mass black holes, Astrophysical black holes
Observation of Gravitational Waves from the Coalescence of a 2.5─4.5 M <SUB>⊙</SUB> Compact Object and a Neutron Star. We report the observation of a coalescing compact binary with component masses 2.5─4.5 M ⊙ and 1.2─2.0 M ⊙ (all measurements quoted at the 90% credible level). The gravitational-wave signal GW230529_181500 was observed during the fourth observing run of the LIGO─Virgo─KAGRA detector network on 2023 May 29 by the LIGO Livingston observatory. The primary component of the source has a mass less than 5 M ⊙ at 99% credibility. We cannot definitively determine from gravitational-wave data alone whether either component of the source is a neutron star or a black hole. However, given existing estimates of the maximum neutron star mass, we find the most probable interpretation of the source to be the coalescence of a neutron star with a black hole that has a mass between the most massive neutron stars and the least massive black holes observed in the Galaxy. We provisionally estimate a merger rate density of  55−47+127Gpc−3yr−1  for compact binary coalescences with properties similar to the source of GW230529_181500; assuming that the source is a neutron star─black hole merger, GW230529_181500-like sources may make up the majority of neutron star─black hole coalescences. The discovery of this system implies an increase in the expected rate of neutron star─black hole mergers with electromagnetic counterparts and provides further evidence for compact objects existing within the purported lower mass gap.

Keywords: Neutron stars, Gravitational wave detectors, Stellar mass black holes, Gravitational wave sources, Gravitational wave astronomy
Radio Signature of the Strong Compression between a Streamer and a Coronal Hole Boundary. We present evidence of the first detection of the radio signature at metric wavelengths of the strong compression between a helmet streamer (HS) and the boundary of a coronal hole (CH) using radio observations from the Callisto MEXICO-LANCE and ALASKA-HAARP systems and white-light observations obtained by the STEREO-A/COR1-COR2 coronagraphs. The event occurred very close to the Sun (∼3.4 solar radii) and produced an intense and unusually broad drifting radio feature at metric wavelengths after a downward-drifting band of emission related to a metric Type II radio burst. The compression is caused by the interaction between an expanding structure (coronal mass ejection/shock) and the HS against the CH boundary. Observations in white light show a sharp compressive feature that propagates radially outward, while STEREO-A/EUVI images show loop oscillations at the same position angle, indicating that the interaction occurs across a range of heights. The loop oscillations cease when the compressive front loses its sharp boundary. This transition indicates a reduction of the density compression at the front and the cessation of the radio emission.

Keywords: Solar coronal mass ejection shocks, Radio bursts, Solar radio emission, Solar coronal mass ejections, Solar coronal holes, Solar coronal streamers
Evaluation of Scale-dependent Kurtosis with HelioSwarm. Plasma turbulence involves complex, nonlinear interactions of electromagnetic fields and charged particles across multiple scales. Studying these phenomena in space plasmas, like the solar wind, is facilitated by the intrinsic scale separations and the availability of in situ spacecraft observations. However, the single-point or single-scale configurations of current spacecraft limit our understanding of many properties of the turbulent solar wind. To overcome these limitations, multipoint measurements spanning a range of characteristic scales are essential. This Letter prepares for the enhanced measurement capabilities of upcoming multispacecraft missions by demonstrating that higher-order statistics, specifically kurtosis, as a baseline for intermittency can be accurately measured. Using synthetic turbulent fields with adjustable intermittency levels, we achieve scale separations analogous to those in the solar wind and apply these techniques to the planned trajectories of the HelioSwarm mission. This approach promises significant advancements in our understanding of plasma turbulence.

Keywords: Interplanetary turbulence, Solar wind, Theoretical techniques
Injection Process of Pickup Ion Acceleration at an Oblique Heliospheric Termination Shock. The injection process of pickup ion acceleration at a heliospheric termination shock is investigated. Using two-dimensional fully kinetic particle-in-cell simulation, accelerated pickup ions are self-consistently reproduced by tracking long time evolution of shocks with an unprecedentedly large system size in the shock normal direction. Reflected pickup ions drive upstream large-amplitude waves through resonant instabilities. Convection of the large-amplitude waves causes shock surface reformation and alters the downstream electromagnetic structure. A part of pickup ions are accelerated to tens of upstream flow energy in the timescale of ∼100 times inverse ion gyrofrequency. The initial acceleration occurs through the shock surfing acceleration (SSA) mechanism followed by the shock drift acceleration mechanism. Large electrostatic potential accompanied by the upstream waves enables the SSA to occur.

Keywords: Heliosphere
Enhanced Efficiency of Solar Wind Electron Interaction with Whistlers Caused by Switchback-related Magnetic Dips. Through test particle simulations based on solar wind observations by the Parker Solar Probe (PSP) mission, we demonstrate that a magnetic gradient can significantly enhance the efficiency of scattering and energization of the strahl electrons by quasi-parallel whistlers, through the phase trapping effect due to the gyrosurfing mechanism. We identify quasi-linear and nonlinear regimes of these interactions for different combinations of wave amplitude (B  w /B 0) and the strength of the magnetic field gradient with magnetic field depletion level (B  h /B 0) as a proxy. Nonlinear effects are observed for B  w /B 0 ≳ 10−3 and B  h /B 0 ≳ 0.1. We estimated the extending of the resonant energy range due to the wave and the magnetic field gradient interplay and demonstrated that these mechanisms result in the broadening of the strahl electron pitch-angle distribution typically observed in situ. The combination of parallel whistlers collocated with a magnetic gradient is frequently observed by PSP in magnetic dips at the edges of magnetic switchbacks. Our results indicate that these mechanisms may be highly relevant for pitch-angle scattering of the strahl electrons and regulating the heat flux near the Sun at heliocentric distances of 30─45 R  S . Specifically, core and halo electrons may experience a 10% increase in their initial energy, and the majority of strahl electrons may be scattered (by an average of 30°) into the hot and trapped plasma inside magnetic dips.

Keywords: Solar wind
Discovery of a Barium Blue Straggler Star in M67 and "Sighting" of Its White Dwarf Companion. We report the discovery of a barium blue straggler star (BSS) in M67, exhibiting enhancements in slow neutron-capture (s-)process elements. Spectroscopic analysis of two BSSs (WOCS 9005 &amp; WOCS 1020) and four stars located near the main-sequence turn-off using GALAH spectra, showed that WOCS 9005 has a significantly high abundance of the s-process elements ([Ba/Fe] = 0.75 ± 0.08, [Y/Fe] = 1.09 ± 0.07, and [La/Fe] = 0.65 ± 0.06). The BSS (WOCS 9005) is a spectroscopic binary with a known period, eccentricity, and a suspected white dwarf (WD) companion with a kinematic mass of 0.5 M ⊙. The first "sighting" of the WD in this barium BSS is achieved through multiwavelength spectral energy distribution (SED) with the crucial far-UV data from the UVIT/AstroSat. The parameters of the hot and cool companions are derived using binary fits of the SED using two combinations of models, yielding a WD with T eff in the range 9750–15,250 K. Considering the kinematic mass limit, the cooling age of the WD is estimated as ∼60 Myr. The observed enhancements are attributed to a mass transfer (MT) from a companion asymptotic giant branch star, now a WD. We estimate the accreted mass to be 0.15 M ⊙, through wind accretion, which increased the envelope mass from 0.45 M ⊙. The detection of chemical enhancement, as well as the sighting of WD in this system, have been possible due to the recent MT in this binary, as suggested by the young WD. * This is paper XV of the UVIT Open Cluster Study (UOCS).

Keywords: White dwarf stars, Spectroscopic binary stars, Blue straggler stars, Spectral energy distribution, Open star clusters, Barium stars, S-process
Direct Observational Evidence of Multi-epoch Massive Star Formation in G24.47+0.49. Using new continuum and molecular line data from the Atacama Large Millimeter/submillimeter Array Three-millimeter Observations of Massive Star-forming Regions (ATOMS) survey and archival Very Large Array, 4.86 GHz data, we present direct observational evidence of hierarchical triggering relating three epochs of massive star formation in a ringlike H II region, G24.47+0.49. We find from radio flux analysis that it is excited by a massive star(s) of spectral type O8.5V–O8V from the first epoch of star formation. The swept-up ionized ring structure shows evidence of secondary collapse, and within this ring, a burst of massive star formation is observed in different evolutionary phases, which constitutes the second epoch. ATOMS spectral line (e.g., HCO+(1–0)) observations reveal an outer concentric molecular gas ring expanding at a velocity of ∼9 km s‑1, constituting the direct and unambiguous detection of an expanding molecular ring. It harbors twelve dense molecular cores with surface mass density greater than 0.05 g cm‑2, a threshold typical of massive star formation. Half of them are found to be subvirial and thus in gravitational collapse making them the third epoch of potential massive star-forming sites.

Keywords: Star forming regions, Star formation, Interstellar medium
Modeling Time-variable Elemental Abundances in Coronal Loop Simulations. Numerous recent X-ray observations of coronal loops in both active regions and solar flares have shown clearly that elemental abundances vary with time. Over the course of a flare, they have been found to move from coronal values toward photospheric values near the flare peak, before slowly returning to coronal values during the gradual phase. Coronal loop models typically assume that the elemental abundances are fixed, however. In this work, we introduce a time-variable abundance factor into the 0D ebtel++ code that models the changes due to chromospheric evaporation in order to understand how this affects coronal loop cooling. We find that for strong heating events (≳1 erg s‑1 cm‑3), the abundances quickly tend towards photospheric values. For smaller heating rates, the abundances fall somewhere between coronal and photospheric values, causing the loop to cool more quickly than the time-fixed photospheric cases (typical flare simulations) and more slowly than time-fixed coronal cases (typical AR simulations). This suggests heating rates in quiescent AR loops no larger than ≈0.1 erg s‑1 cm‑3 to be consistent with recent measurements of abundance factors f ≳ 2.

Keywords: Solar coronal loops, The Sun, Solar coronal heating, Solar flares
Bumpy Superluminous Supernovae Powered by a Magnetar–Star Binary Engine. Wolf–Rayet stars in close binary systems can be tidally spun up by their companions, potentially leaving behind fast-spinning, highly magnetized neutron stars, known as "magnetars," after core collapse. These newborn magnetars can transfer rotational energy into heating and accelerating the ejecta, producing hydrogen-poor superluminous supernovae (SLSNe). In this Letter, we propose that the magnetar wind of the newborn magnetar could significantly evaporate its companion star, typically a main-sequence or helium star, if the binary system is not disrupted by the abrupt mass loss and supernova (SN) kick. The subsequent heating and acceleration of the evaporated star material along with the SN ejecta by the magnetar wind can produce a postpeak bump in the SLSN lightcurve. Our model can reproduce the primary peaks and postpeak bumps of four example observed multiband SLSN lightcurves, revealing that the mass of the evaporated material could be ∼0.4–0.6 M ⊙ if the material is hydrogen-rich. We propose that the magnetar could induce strongly enhanced evaporation from its companion star near the pericenter if the orbit of the post-SN binary is highly eccentric, ultimately generating multiple postpeak bumps in the SLSN lightcurves. This "magnetar–star binary engine" model may offer a possible explanation for the evolution of polarization, along with the origin and velocity broadening of late-time hydrogen or helium broad spectral features observed in some bumpy SLSNe. The diversity in the lightcurves and spectra of SLSNe may be attributed to the wide variety of companion stars and post-SN binary systems.

Keywords: Close binary stars, Magnetars, Light curves, Supernovae
The Relationship between Kinetic and Magnetic Helicity in Solar Active Regions. Using Helioseismic and Magnetic Imager/Solar Dynamics Observatory data, we search for a relationship between kinetic helicity and magnetic helicity in solar active regions (ARs) using a sample of 62 ARs from 2010 May to 2015 May. The sample includes 32 mature ARs and 30 emerging ARs. We calculate kinetic helicity in the interior in the depth range from 0.6 to 11.6 Mm, magnetic helicity in the corona, helicity flux across the photosphere, and the magnetic twist and magnetic writhe of the ARs at the photosphere. From these data, relationships are found between magnetic helicity, helicity flux, and magnetic twist. However, magnetic writhe appears not to be related to the other magnetic quantities. No relationship is found between the kinetic helicity and any magnetic quantity. In particular, no relationship is found between the kinetic helicity and any of the following: magnetic helicity, magnetic helicity flux, magnetic twist, or magnetic writhe. These results suggest that (1) the magnetic helicity in the corona above ARs is mainly derived from the magnetic twist, and (2) the flow dynamics in the region from 0.6 to 11.6 Mm below the photosphere is not the primary source for the generation of magnetic helicity in ARs.

Keywords: Solar active region magnetic fields, Solar dynamo, Solar photosphere, Solar interior
The Plasma Pressure Contribution from Low-energy (0.05–2 keV) Energetic Neutral Atoms in the Heliosheath. Energetic neutral atoms (ENAs) from the heliosphere are a unique means to remotely image the boundary regions of our heliosphere. The Interstellar Boundary Explorer (IBEX) has been very successful in measuring these ENAs since 2008 at energies from tens of eV to 6 keV. The main question raised by one solar cycle of IBEX-Lo observations at 0.05–2 keV is the strong and ubiquitous underestimation of several model predictions compared with actually measured ENA intensities at energies between 100 and 500 eV. This study converts the observed ENA intensities into plasma pressures for different sky directions and considers the implications for our understanding of the heliosheath and the source of the observed ENAs.

Keywords: Heliosheath, Space plasmas, Heliosphere
Collisionless Shock in a Relativistically Hot Unmagnetized Electron–Positron Plasma. In this work, we investigate collisionless shocks propagating in a relativistically hot unmagnetized electron–positron plasma. We estimate the dissipation fraction at shocks in the relativistically hot plasma, showing that it is sufficiently large to explain the observation of gamma-ray bursts even when the shock is not highly relativistic. It is shown by two-dimensional particle-in-cell simulations that magnetic fields are generated around the shock front by the Weibel instability, as in the cold upstream plasma. However, in contrast to the cold upstream plasma, no particles are accelerated at the shock in the simulation time of  t=3600ωp‑1 . The decay of the magnetic field in the downstream region is slower for slower shock velocities in the hot plasma cases. Applying the slow decay of the downstream magnetic field, we propose a model that generates magnetic fields in the large downstream region, which is required from the standard model of the gamma-ray burst afterglow.

Keywords: Gamma-ray bursts, High energy astrophysics, Plasma physics, Plasma astrophysics, Shocks