Sazuna/UAT_keywords huggingface dataset:
Entrapment in CO<SUB>2</SUB> and H<SUB>2</SUB>O Ices: Impact of Ice Matrix Thickness. The volatile inventories of planets depend on the precise partitioning of different volatiles between the gas and solid phases across the planet birth disk. For the case of hyper-volatiles (e.g., CO, N2, and noble gases), the partitioning also depends on how efficiently they are trapped into less volatile ice matrices. The thicknesses of these ice matrices can range from a few molecular layers to macroscopic bodies, and in this study we explore how entrapment efficiency depends on the ice thickness between tens of nanometers and a few micrometers (∼50–3000 monolayers, ML). We carry out a series of temperature-programmed desorption (TPD) experiments on H2O:CO and CO2:CO mixtures with 5:1 and 15:1 matrix-to-CO mixing ratios. Entrapment efficiencies range from 41% to 64%, with higher entrapment efficiencies for the more dilute ices. Surprisingly, we find no significant difference in entrapment across the studied ice thicknesses for either H2O or CO2 ice matrices. Complementary TPD experiments with the additional hyper-volatiles N2 and Ar see a similar trend with ice thickness. We speculate that these results may be due to surface topography such as cracks that lead to hyper-volatile escape from deep ice layers. In either case, these experiments show that entrapment in microscopic ices is relatively insensitive to ice thickness (above ∼50 ML). In protoplanetary disks we therefore expect efficient entrapment in icy grains of a range of grain sizes.

Keywords: Molecular data, Chemical abundances, Astrochemistry, Planetary system formation, Protoplanetary disks, Planet formation
A Closer Look at the Extended Edge-on Low-surface Brightness Galaxies. To understand the origin of extended disks of low-surface brightness (LSB) galaxies, we studied in detail four such systems with large disks seen edge on. Two of them are edge-on giant LSB galaxies (gLSBGs) recently identified by our team. The edge-on orientation of these systems boosts their surface brightnesses that provided an opportunity to characterize stellar populations spectroscopically and yielded the first such measurements for edge-on gLSBGs. We collected deep images of one galaxy using the 1.4 m Milanković Telescope, which we combined with the archival Subaru Hyper Suprime-Cam and DESI Legacy Surveys data available for the three other systems, and measured the structural parameters of the disks. We acquired deep long-slit spectra with the Russian 6 m telescope and the 10 m Keck II telescope and estimated stellar population properties in the high-surface brightness and LSB regions as well as the gas-phase metallicity distribution. The gas metallicity gradients are shallow to flat in the range between 0 and ‑0.03 dex per exponential disk scale length, which is consistent with the extrapolation of the gradient–scale length relation for smaller disk galaxies. Our estimates of stellar velocity dispersion in the LSB disks as well as the relative thickness of the disks indicate the dynamical overheating. Our observations favor mergers as the essential stage in the formation scenario for massive LSB galaxies.

Keywords: Galaxy formation, Galaxy physics, Galaxy rotation, Galaxy evolution
Angular Momentum Loss during Stable Mass Transfer onto a Compact Object: The Effect of Mass Loss via Accretion Disk Winds. We use an analytic framework to calculate the evolution of binary orbits under a physically motivated model that accounts for angular momentum loss associated with winds from an accretion disk around the compact-objected accretor. Our prescription considers wind mass ejection from the surface of an accretion disk, accounting for a radial mass-loss dependence across the disk surface. We compare this to the standard prescription of angular momentum loss associated with isotropic mass loss from the vicinity of the accretor. The angular momentum loss from a disk wind is always larger. For mass ratios, q, between 2 and 10, angular momentum loss via a disk wind can be ≃3–40 times greater than the standard prescription. For the majority of mass ratios and disk properties, accounting for the disk wind can result in considerably smaller orbital separations compared to the standard formalism, the differences being ≃60% depending on how long the effect is integrated for. We conclude that it is important to consider the effects of angular momentum loss from a disk wind when evolving binary orbits.

Keywords: Neutron stars, X-ray binary stars, Black holes, Interacting binary stars, Gravitational wave sources, Roche lobe overflow
MOSEL Survey: Spatially Offset Lyman-continuum Emission in a New Emitter at z = 3.088 Can Explain the Low Number Density of Observed LyC Leakers. We present the discovery of a unique Lyman-continuum (LyC) emitter at z = 3.088. The LyC emission was detected using the Hubble Space Telescope WFC3/UVIS F336W filter, covering a rest-frame wavelength range of 760─900 Å. The peak signal-to-noise ratio of LyC emission is 3.9 in an r = 0.″24 aperture and is spatially offset by 0.″29 ± 0.″04 (∼2.2 ± 0.3 kpc) from the peak of rest-UV emission (F606W). By combining imaging and spectroscopic data from the James Webb Space Telescope (JWST) JADES, FRESCO, and JEMS surveys, along with VLT/MUSE data from the MXDF survey, we estimate that the probability of random alignment with an interloper galaxy causing the LyC emission is less than 6 × 10−5. The interstellar medium (ISM) conditions in the galaxy are similar to those in other LyC emitters at high redshift ( 12+log(O/H)=7.79−0.05+0.06 ,  logU=−3.27−0.12+0.14 , O32 = 0.63 ± 0.03), although the single-peaked Lyα profile and lack of rest-UV emission lines suggest an optically thick ISM. Our observations indicate that LyC photons are leaking through a narrow cone of optically thin neutral ISM, most likely created by a past merger (as evidenced by medium-band F210M and F182M images). Using the constraints on escape fraction from individual leakers and a simple model, we estimate that the opening half-angle of ionization cones can be as small as 16° (2% ionized fraction) to reproduce some of the theoretical constraints on the average escape fraction for galaxies. The narrow opening angle required can explain the low number density of confirmed LyC leakers.

Keywords: Lyman-alpha galaxies, High-redshift galaxies, Galaxy evolution, Emission line galaxies
Brightening and Fading in the Youngest Galactic Supernova Remnant G1.9+0.3: 13 Years of Monitoring with the Chandra X-Ray Observatory. We report 13 years of Chandra monitoring of the youngest Galactic supernova remnant G1.9+0.3, the only remnant known to be increasing in brightness. We confirm the spatially integrated rate of flux increase of (1.2 ± 0.2)% yr‑1 (1–7 keV), but find large spatial variations, from ‑3% yr‑1 to +7% yr‑1, over length scales as small as 10″ or smaller. We observe relatively little change in spectral slope, though one region shows significant hardening as it brightens by 1% yr‑1. Such rates of change can be accommodated by any of several explanations, including steady blast-wave evolution, expansion or compression of discrete plasma blobs, magnetic turbulence, or variations in magnetic-field aspect angle. Our results do not constrain the mean magnetic-field strength, but a self-consistent picture can be produced in which the maximum particle energies are limited by the remnant age (applying both to electrons and to ions) to about 20 TeV, and the remnant-averaged magnetic-field strength is about 30 μG. The deceleration parameter m (average shock radius varying as t  m ) is about 0.7, consistent with estimates from overall expansion dynamics and confirming an explosion date of about 1900 CE. Shock-efficiency factors ϵ  e  and ϵ  B  (fractions of shock energy in relativistic electrons and magnetic field) are 0.003 and 0.0002 in this picture. However, the large range of rates of brightness change indicates that such a global model is oversimplified. Temporal variations of photon index, expected to be small but measurable with longer time baselines, can discriminate among possible models.

Keywords: Supernova remnants, Cosmic ray sources, X-ray sources
Solar Orbiter Observations of Proton and Alpha Particle Kinetic Signatures Related to the Presence of Switchbacks in the Inner Heliosphere: A Case Study. We investigate how ions, namely protons and alpha particles, kinetically react to the presence of strong deflections in the magnetic field, the so-called switchbacks, in the first stream of slow Alfvénic wind observed by Solar Orbiter at the heliocentric distance of 0.64 au. We focus on an isolated, large-scale switchback, and we study in detail ion kinetic properties. Beyond the expected correlation between the magnetic deflection and ion velocity related to the Alfvénic nature of the switchbacks, we find that, within the switchback, proton and alpha particle densities increase, suggesting ongoing wave activity. Very interestingly, we observe a clear correlation between the magnetic deflection and alpha particle temperature, while no correlation has been found with proton temperature. This is an indication of a possible role played by switchbacks in preferentially heating heavy ions. Our results suggest that the presence of switchbacks can induce a deformation of the proton velocity distribution function, while the preferential heating of alpha particles could be due to a denser secondary beam and a smaller relative drift speed between the beam and core.

Keywords: Interplanetary turbulence, Solar wind, Heliosphere
Analysis of Crab X-Ray Polarization Using Deeper Imaging X-Ray Polarimetry Explorer Observations. We present Crab X-ray polarization measurements using Imaging X-Ray Polarimetry Explorer (IXPE) data with a total exposure of 300 ks, three times more than the initial 2022 discovery paper. Polarization is detected in three times more pulsar phase bins, revealing an S-shaped +40° polarization angle sweep in the main pulse and &gt;1σ departures from the OPTIMA optical polarization in both pulses, suggesting different radiation mechanisms or sites for the polarized emission at the two wavebands. Our polarization map of the inner nebula reveals a toroidal magnetic field, as seen in prior IXPE analyses. Along the southern jet, the magnetic field orientation relative to the jet axis changes from perpendicular to parallel and the polarization degree decreases by ∼6%. These observations may be explained by kink instabilities along the jet or a collision with a dense, jet-deflecting medium at the tip. Using spectropolarimetric analysis, we find asymmetric polarization in the four quadrants of the inner nebula, as expected for a toroidal field geometry, and a spatial correlation between polarization degree and photon index.

Keywords: X-ray astronomy, Polarimetry, Pulsars, Pulsar wind nebulae
Mapping Multiphase Metals in Star-forming Galaxies: A Spatially Resolved UV+Optical Study of NGC 5253. We present a pioneering, spatially resolved, multiphase gas abundance study on the blue compact dwarf galaxy NGC 5253, targeting 10 star-forming (SF) clusters inside six far-UV (FUV) Hubble Space Telescope/Cosmic Origins Spectrograph (COS) pointings with cospatial optical Very Large Telescope/MUSE observations throughout the galaxy. The SF regions span a wide range of ages (1─15 Myr) and are distributed at different radii (50─230 pc). We performed a robust absorption-line profile fitting on the COS spectra, covering 1065─1430 Å in the FUV, allowing an accurate computation of neutral-gas abundances for 13 different ions sampling eight elements. These values were then compared with the ionized-gas abundances, measured using the direct method on MUSE integrated spectra inside analog COS apertures. Our multiphase, spatially resolved comparisons find abundances, which are lower in the neutral gas than the ionized gas by 0.22, 0.80, and 0.58 dex for log(O/H), log(N/H), and log(N/O), respectively. We modeled the chemical abundance distributions and evaluated correlations as a function of the radius and age. It was found that, while N, O, and N/O abundances decrease as a function of age in the ionized gas, they increase with age in the neutral gas. No strong correlations for N, O, or N/O were observed as a function of the radius. The N/O and N/H offsets between the phases were found to decrease with age, providing evidence that chemical enrichment happens differentially, first in the ionized-gas phase around 2─5 Myrs (due to N-rich Wolf─Rayet stars) and then mixing out into the cold neutral gas on longer timescales of 10─15 Myr.

Keywords: Starburst galaxies, Galaxy chemical evolution, Ultraviolet spectroscopy, Chemical enrichment, Galaxy abundances, Galaxy evolution, Interstellar medium
Periodic Coronal Rain Driven by Self-consistent Heating Process in a Radiative Magnetohydrodynamic Simulation. The periodic coronal rain and in-phase radiative intensity pulsations have been observed in multiple wavelengths in recent years. However, due to the lack of three-dimensional coronal magnetic fields and thermodynamic data in observations, it remains challenging to quantify the coronal heating rate that drives the mass cycles. In this work, based on the MURaM code, we conduct a three-dimensional radiative magnetohydrodynamic simulation spanning from the convective zone to the corona, where the solar atmosphere is heated self-consistently through dissipation resulting from magnetoconvection. For the first time, we model the periodic coronal rain in an active region. With a high spatial resolution, the simulation well resembles the observational features across different extreme-ultraviolet wavelengths. These include the realistic interweaving coronal loops, periodic coronal rain, and periodic intensity pulsations, with two periods of 3.0 hr and 3.7 hr identified within one loop system. Moreover, the simulation allows for a detailed three-dimensional depiction of coronal rain on small scales, revealing adjacent shower-like rain clumps ∼500 km in width and showcasing their multithermal internal structures. We further reveal that these periodic variations essentially reflect the cyclic energy evolution of the coronal loop under thermal nonequilibrium state. Importantly, as the driver of the mass circulation, the self-consistent coronal heating rate is considerably complex in time and space, with hour-level variations in 1 order of magnitude, minute-level bursts, and varying asymmetry reaching ten times between footpoints. This provides an instructive template for the ad hoc heating function and further enhances our understanding of the coronal heating process.

Keywords: Radiative magnetohydrodynamics, Solar extreme ultraviolet emission, Solar coronal loops, Solar convective zone, Solar coronal heating, Solar active regions, Solar corona, Solar magnetic fields
Not-so-little Red Dots: Two Massive and Dusty Starbursts at z ∼ 5─7 Pushing the Limits of Star Formation Discovered by JWST in the COSMOS-Web Survey. We present the properties of two candidate massive (M ⋆ ∼ 1011 M ⊙) and dusty (A v &gt; 2.5 mag) galaxies at z = 5─7 in the first 0.28 deg2 of the COSMOS-Web survey. One object is spectroscopically confirmed at z spec = 5.051, while the other has a robust z phot = 6.7 ± 0.3. Thanks to their extremely red colors (F277W─F444W ∼ 1.7 mag), these galaxies satisfy the nominal color selection for the widely studied "little red dot" (LRD) population with the exception of their spatially resolved morphologies. The morphology of our targets allows us to conclude that their red continuum is dominated by highly obscured stellar emission and not by reddened nuclear activity. Using a variety of spectral energy distribution fitting tools and star formation histories, we estimate the stellar masses to be  log(M⋆)=11.32−0.15+0.07M⊙  and  log(M⋆)=11.2−0.2+0.1M⊙ , respectively, with a red continuum emission dominated by a recent episode of star formation. We then compare their number density to the halo mass function to infer stellar baryon fractions of ϵ ⋆ ∼ 0.25 and ϵ ⋆ ∼ 0.5. Both are significantly higher than what is commonly observed in lower-z galaxies or more dust-obscured galaxies at similar redshifts. With very bright ultra-high-z Lyman-Break Galaxies and some non-AGN-dominated LRDs, such "extended" LRDs represent another population that may require very efficient star formation at early times.

Keywords: Galaxy formation, Star formation, Galaxy evolution, High-redshift galaxies, Galaxies
Neglected Silicon Dioxide Polymorphs as Clouds in Substellar Atmospheres. Direct mid-infrared signatures of silicate clouds in substellar atmospheres were first detected in Spitzer observations of brown dwarfs, although their existence was previously inferred from near-infrared spectra. With JWST's Mid-Infrared Instrument, we can now more deeply probe silicate features from 8 to 10 μm, exploring specific particle composition, size, and structure. Recent characterization efforts have led to the identification of silica (silicon dioxide, SiO2) cloud features in brown dwarfs and giant exoplanets. Previous modeling, motivated by chemical equilibrium, has primarily focused on magnesium silicates (forsterite, enstatite), crystalline quartz, and amorphous silica to match observations. Here, we explore the previously neglected possibility that other crystalline structures of silica, i.e., polymorphs, may be more likely to form at the pressure and temperature conditions of substellar upper atmospheres. We evaluate JWST's diagnostic potential for these polymorphs and find that existing published transmission data are only able to conclusively distinguish tridymite, but future higher signal-to-noise ratio transmission observations, directly imaged planet observations, and brown dwarf observations may be able to disentangle all four of the silica polymorphs. We ultimately propose that accounting for the distinct opacities arising from the possible crystalline structure of cloud materials may act as a powerful, observable diagnostic tracer of atmospheric conditions, where particle crystallinity records the history of the atmospheric regions through which clouds formed and evolved. Finally, we highlight that high-fidelity, accurate laboratory measurements of silica polymorphs are critically needed to draw meaningful conclusions about the identities and structures of clouds in substellar atmospheres.

Keywords: Silicate grains, Theoretical models, Atmospheric clouds, Laboratory astrophysics, L dwarfs, Planetary mineralogy, Transmission spectroscopy, James Webb Space Telescope, Spectroscopy, Atmospheric dynamics, Exoplanet atmospheres
The Distribution of Planet Radius in Kepler Multiplanet Systems Depends on Gap Complexity. The distribution of small planet radius (&lt;4 R ⊕) is an indicator of the underlying processes governing planet formation and evolution. We investigate the correlation between the radius distribution of exoplanets in Kepler multiplanet systems and the system-level complexity in orbital period spacing. Utilizing a sample of 234 planetary systems with three or more candidate planets orbiting FGK main-sequence stars, we measure the gap complexity (C) to characterize the regularity of planetary spacing and compare it with other measures of period spacing and spacing uniformity. We find that systems with higher gap complexity exhibit a distinct radius distribution compared to systems with lower gap complexity. Specifically, we find that the radius valley, which separates super-Earths and sub-Neptunes, is more pronounced in systems with lower gap complexity (C &lt; 0.165). Planets in high-complexity systems (C &gt; 0.35) exhibit a lower frequency of sub-Earths (2.5 times less) and sub-Neptunes (1.3 times less) and a higher frequency of super-Earths (1.4 times more) than planets in low-complexity systems. This may suggest that planetary systems with more irregular spacings are more likely to undergo dynamic interactions that influence planet scattering, composition, and atmospheric retention. The gap complexity metric proves to be a valuable tool in linking the orbital configurations of planets to their physical characteristics.

Keywords: Planetary system formation, Exoplanet systems, Exoplanets
Time Evolution Images of the Hypergiant RW Cephei during the Rebrightening Phase Following the Great Dimming. Stars with initial masses larger than 8 M ⊙ undergo substantial mass loss through mechanisms that remain elusive. Unraveling the origins of this mass loss is important for comprehending the evolutionary path of these stars, the type of supernova explosion, and whether they become neutron stars or black hole remnants. In 2022 December, RW Cep experienced the Great Dimming in its visible brightness, presenting a unique opportunity to understand mass-loss mechanisms. Our previous observations of RW Cep from the CHARA Array, taken during the dimming phase, show a compelling asymmetry in the star images, with a darker zone on the west side of the star indicating the presence of dust in front of the star in our line of sight. Here, we present multiepoch observations from CHARA while the star rebrightened in 2023. We created images using three image reconstruction methods and an analytical model fit. Comparisons of images acquired during the dimming and rebrightening phases reveal remarkable differences. Specifically, the west side of RW Cep, initially obscured during the dimming phase, reappeared during the subsequent rebrightening phase, and the measured angular diameter became larger by 8%. We also observed image changes from epoch to epoch while the star is brightening, indicating the time evolution of dust in front of the star. We suggest that the dimming of RW Cep was a result of a recent surface mass ejection event, generating a dust cloud that partially obstructed the stellar photosphere.

Keywords: Yellow hypergiant stars, Stellar radii, Stellar mass loss, Long period variable stars, Late-type supergiant stars, Hypergiant stars
New 511 keV Line Data Provide Strongest sub-GeV Dark Matter Constraints. We explore the 511 keV emission associated with sub-GeV dark matter (DM) particles that can produce electron─positron pairs and form positronium after thermalizing. We use ∼16 yr of data from the Spectrometer on INTEGRAL to constrain DM properties, including the full positron propagation and losses, and the suppression of free electron density away from the Galactic plane. We show that the predicted longitude and latitude profiles vary significantly for different DM masses, unlike previous assumptions, and obtain the strongest limits on sub-GeV DM (from the MeV to a few GeV) so far, excluding cross sections down to &lt;σ v&gt; ≲ 10−32 cm3 s−1 for m  χ  ∼ 1 MeV and &lt;σ v&gt; ≲ 10−26 cm3 s−1 for m  χ  ∼ 5 GeV and lifetimes up to τ ≳ 1029 s for m  χ  ∼ 1 MeV and τ ≳ 1027 s for m  χ  ∼ 5 GeV for the typical Navarro─Frenk─White DM profile. Our derived limits are robust within a factor of a few due to systematic uncertainties.

Keywords: Milky Way dark matter halo, Cosmic ray astronomy, Particle astrophysics