Sazuna/UAT_keywords huggingface dataset:
Implications of Evaporative Cooling by H<SUB>2</SUB> for 1I/'Oumuamua. The first interstellar object observed in our solar system, 1I/'Oumuamua, exhibited several peculiar properties, including extreme elongation and nongravitational acceleration. Bergner &amp; Seligman (hereafter BS23) proposed that evaporation of trapped H2 created by cosmic rays can explain the nongravitational acceleration. However, their modeling of the thermal structure of 1I/'Oumuamua ignored the crucial cooling effect of evaporating H2. By taking into account the cooling by H2 evaporation, we show that the surface temperature of H2-water ice is a factor of 9 lower than the case without evaporative cooling. As a result, the thermal speed of outgassing H2 is decreased by a factor of 3. Our one-dimensional thermal modeling that takes into account evaporative cooling for two chosen values of thermal conductivity of κ = 0.01 and 0.1 WK-1 m-1 shows that the water ice volume available for H2 sublimation at T &gt; 30 K would be reduced by a factor of 9 and 5 compared to the results of BS23, not enabling enough hydrogen to propel 1I/'Oumuamua.

Keywords: Ice physics, Astronomical object identification, Ocean planets, Interstellar objects
A Model for Confined Solar Eruptions Including External Reconnection. The violent disruption of the coronal magnetic field is often observed to be restricted to the low corona, appearing as a confined eruption. The possible causes of the confinement remain elusive. Here, we model the eruption of a magnetic flux rope in a quadrupolar active region, with the parameters set such that magnetic X-lines exist both below and above the rope. This facilitates the onset of magnetic reconnection in either place but with partly opposing effects on the eruption. The lower reconnection initially adds poloidal flux to the rope, increasing the upward hoop force and supporting the rise of the rope. However, when the flux of the magnetic side lobes enters the lower reconnection, the flux rope is found to separate from the reconnection site and the flux accumulation ceases. At the same time, the upper reconnection begins to reduce the poloidal flux of the rope, decreasing its hoop force; eventually this cuts the rope completely. The relative weight of the two reconnection processes is varied in the model, and it is found that their combined effect and the tension force of the overlying field confine the eruption if the flux ratio of the outer to the inner polarities exceeds a threshold, which is ~1.3 for our Cartesian box and chosen parameters. We hence propose that external reconnection between an erupting flux rope and overlying flux can play a vital role in confining eruptions.

Keywords: Magnetohydrodynamics, Solar flares, Solar coronal mass ejections, Solar magnetic reconnection
Rejuvenating Star Formation Activity in an Early-type Dwarf Galaxy, LEDA 1915372, with Accreted H I Gas. We report a rare astrophysical phenomenon, in which an early-type dwarf galaxy (dE), LEDA 1915372, is accreting gas from a nearby star-forming dwarf galaxy, MRK 0689, and is rejuvenating star formation activity at the center. Both LEDA 1915372 and MRK 0689 have similar brightness of M  r  = -16.99 and -16.78 mag, respectively. They are located in a small group environment, separated by a sky-projected distance of 20.27 kpc (up to 70 kpc in three dimension), and have a relative line-of-sight radial velocity of 6 km s-1. The observation of 21 cm emission with the Giant Metrewave Radio Telescope provides strong evidence of interaction between the pair of dwarf galaxies in terms of neutral hydrogen (HI) morphology and kinematics. In particular, the HI map reveals that the two galaxies are clearly connected by a gas bridge, and the gas components of both LEDA 1915372 and MRK 0689 share a common direction of rotation. We also find that the HI emission peak deviates from LEDA 1915372 toward its optical blue plume, suggesting a tidal origin of ongoing central star formation. Our findings provide a new path to the formation of blue-cored dEs.

Keywords: Dwarf galaxies, Early-type galaxies, Galaxy interactions
Discovery and Timing Analysis of New Pulsars in Globular Cluster NGC 5024: New Observations from FAST. The most distant globular cluster (GC) with known pulsars is NGC 5024 (M53). In this paper, we report the discovery of a new binary millisecond pulsar, PSR J1312+1810E (M53E), and present the new timing solutions for M53B-E based on 22 observations from the Five-hundred-meter Aperture Spherical radio Telescope (FAST). These discoveries and timing work benefit from FAST's high sensitivity. We find that M53C is the only isolated millisecond pulsar known in this distant GC, with a spin period of 12.53 ms and spin period derivative of 5.26 × 10-20 s s-1. Our results reveal orbital periods of 47.7, 5.8, and 2.4 days for M53B, D, and E, respectively. The companions, with masses of 0.25, 0.27, and 0.18 M ⊙, respectively, are likely to be white dwarf stars; if they are extended objects, they do not eclipse the pulsars. We find no X-ray counterparts for these millisecond pulsars in archival Chandra images in the band of 0.3-8 keV. The characteristics of this pulsar population are similar to the population of millisecond pulsars in the Galactic disk, as expected from the low stellar density of M53.

Keywords: Globular star clusters, Radio telescopes, Binary pulsars, Millisecond pulsars
Evidence for Ubiquitous Carbon Grain Destruction in Hot Protostellar Envelopes. Earth is deficient in carbon and nitrogen by up to ~4 orders of magnitude compared with the Sun. Destruction of (carbon- and nitrogen-rich) refractory organics in the high-temperature planet-forming regions could explain this deficiency. Assuming a refractory cometary composition for these grains, their destruction enhances nitrogen-containing, oxygen-poor molecules in the hot gas (≳300 K) after the initial formation and sublimation of these molecules from oxygen-rich ices in the warm gas (~150 K). Using observations of 37 high-mass protostars with the Atacama Large Millimeter/submillimeter Array, we find that oxygen-containing molecules (CH3OH and HNCO) systematically show no enhancement in their hot component. In contrast, nitrogen-containing, oxygen-poor molecules (CH3CN and C2H3CN) systematically show an enhancement of a factor ~5 in their hot component, pointing to additional production of these molecules in the hot gas. Assuming only thermal excitation conditions, we interpret these results as a signature of destruction of refractory organics, consistent with the cometary composition. This destruction implies a higher C/O and N/O in the hot gas than the warm gas, while the exact values of these ratios depend on the fraction of grains that are effectively destroyed. This fraction can be found by future chemical models that constrain C/O and N/O from the abundances of minor carbon, nitrogen, and oxygen carriers presented here.

Keywords: Protostars, Interferometry, Chemical abundances, Astrochemistry
Implications of Atmospheric Nondetections for Trappist-1 Inner Planets on Atmospheric Retention Prospects for Outer Planets. JWST secondary eclipse observations of Trappist-1b seemingly disfavor atmospheres &gt;~1 bar since heat redistribution is expected to yield dayside emission temperature below the ~500 K observed. Given the similar densities of Trappist-1 planets, and the theoretical potential for atmospheric erosion around late M dwarfs, this observation might be assumed to imply substantial atmospheres are also unlikely for the outer planets. However, the processes governing atmosphere erosion and replenishment are fundamentally different for inner and outer planets. Here, an atmosphere-interior evolution model is used to show that an airless Trappist-1b (and c) only weakly constrains stellar evolution, and that the odds of outer planets e and f retaining substantial atmospheres remain largely unchanged. This is true even if the initial volatile inventories of planets in the Trappist-1 system are highly correlated. The reason for this result is that b and c sit unambiguously interior to the runaway greenhouse limit, and so have potentially experienced ~8 Gyr of X-ray and extreme ultraviolet-driven hydrodynamic escape; complete atmospheric erosion in this environment only weakly constrains stellar evolution and escape parameterizations. In contrast, e and f reside within the habitable zone, and likely experienced a comparatively short steam atmosphere during Trappist-1's pre-main sequence, and consequently complete atmospheric erosion remains unlikely across a broad swath of parameter space (e and f retain atmospheres in ~98% of model runs). Naturally, it is still possible that all Trappist-1 planets formed volatile-poor and are all airless today. But the airlessness of b (and c) does not require this, and as such, JWST transit spectroscopy of e and f remains the best near-term opportunity to characterize the atmospheres of habitable zone terrestrial planets.

Keywords: Exoplanet astronomy, Habitable planets, Exoplanets
Templates for Fitting Photometry of Ultra-high-redshift Galaxies. Recent data from the James Webb Space Telescope allow a first glimpse of galaxies at z ≳ 11. The most successful tool for identifying ultra-high-redshift candidates and inferring their properties is photometric template fitting. However, current methods rely on templates derived from much lower-redshift conditions, including stellar populations older than the age of the Universe at z &gt; 12, a stellar initial mass function that is physically disallowed at z &gt; 6, and weaker emission lines than currently observed at z &gt; 7.5. Here, two sets of synthetic templates, optimized for the expected astrophysics of galaxies at 8 &lt; z &lt; 12 and z &gt; 12, are developed and used to fit three galaxies at z &gt; 12 from the SMACS0723 field. Using these improved templates, quantitative estimates are produced of the bias in inferred properties from JWST observations at z &gt; 8 due to these effects. The best-fit redshifts are similar to those found with previous template sets, but the inferred stellar masses drop by as much as 1-1.6 dex, such that stellar masses are no longer seemingly inconsistent with ΛCDM. The two new template sets are released in formats compatible with EAZY and LEPHARE.

Keywords: Initial mass function, Stellar populations, Astronomical techniques, Galaxy photometry, Photometry, High-redshift galaxies
Resolving Galactic-scale Obscuration of X-Ray AGNs at z ≳ 1 with COSMOS-Web. A large fraction of the accreting supermassive black hole population is shrouded by copious amounts of gas and dust, particularly in the distant (z ≳ 1) universe. While much of the obscuration is attributed to a parsec-scale torus, there is a known contribution from the larger-scale host galaxy. Using JWST/NIRCam imaging from the COSMOS-Web survey, we probe the galaxy-wide dust distribution in X-ray selected active galactic nuclei (AGNs) up to z ~ 2. Here, we focus on a sample of three AGNs with their host galaxies exhibiting prominent dust lanes, potentially due to their edge-on alignment. These represent 27% (3 out of 11 with early NIRCam data) of the heavily obscured (N H &gt; 1023 cm-2) AGN population. With limited signs of a central AGN in the optical and near-infrared, the NIRCam images are used to produce reddening maps E(B - V) of the host galaxies. We compare the mean central value of E(B - V) to the X-ray obscuring column density along the line of sight to the AGN (N H ~ 1023-23.5 cm-2). We find that the extinction due to the host galaxy is present (0.6 ≲ E(B - V) ≲ 0.9; 1.9 ≲ A  V  ≲ 2.8) and significantly contributes to the X-ray obscuration at a level of N H ~ 1022.5 cm-2 assuming an SMC gas-to-dust ratio that amounts to ≲30% of the total obscuring column density. These early results, including three additional cases from CEERS, demonstrate the ability to resolve such dust structures with JWST and separate the different circumnuclear and galaxy-scale obscuring structures.

Keywords: AGN host galaxies, Infrared astronomy, X-ray active galactic nuclei, Galactic and extragalactic astronomy
Turbulence-supported Massive Star Envelopes. The outer envelopes of massive (M ≳ 10 M ⊙) stars exhibit large increases in opacities from forests of lines and ionization transitions (particularly from iron and helium) that trigger near-surface convection zones. One-dimensional (1D) models predict density inversions and supersonic motions that must be resolved with computationally intensive three-dimensional (3D) radiation hydrodynamic (RHD) modeling. Only in the last decade have computational tools advanced to the point where ab initio 3D models of these turbulent envelopes can be calculated, enabling us to present five 3D RHD ATHENA++ models (four previously published and one new 13 M ⊙ model). When convective motions are subsonic, we find excellent agreement between 3D and 1D velocity magnitudes, stellar structure, and photospheric quantities. However, when convective velocities approach the sound speed, hydrostatic balance fails as the turbulent pressure can account for 80% of the force balance. As predicted by Henyey, we show that this additional pressure support leads to a modified temperature gradient, which reduces the superadiabaticity where convection is occurring. In addition, all five models display significant overshooting from the convection in the Fe convection zone. As a result, the turbulent velocities at the surface are indicative of those in the Fe zone. There are no confined convection zones as seen in 1D models. In particular, helium convection zones seen in 1D models are significantly modified. Stochastic low-frequency brightness variability is also present in the 13 M ⊙ model with comparable amplitude and characteristic frequency to observed stars.

Keywords: Stellar physics, Stellar structures, Stellar surfaces, Stellar convective zones
Periodic Radio Emission from the T8 Dwarf WISE J062309.94-045624.6. We present the detection of rotationally modulated, circularly polarized radio emission from the T8 brown dwarf WISE J062309.94-045624.6 between 0.9 and 2.0 GHz. We detected this high-proper-motion ultracool dwarf with the Australian SKA Pathfinder in 1.36 GHz imaging data from the Rapid ASKAP Continuum Survey. We observed WISE J062309.94-045624.6 to have a time and frequency averaged Stokes I flux density of 4.17 ± 0.41 mJy beam-1, with an absolute circular polarization fraction of 66.3% ± 9.0%, and calculated a specific radio luminosity of L  ν  ~ 1014.8 erg s-1 Hz-1. In follow-up observations with the Australian Telescope Compact Array and MeerKAT we identified a multipeaked pulse structure, used dynamic spectra to place a lower limit of B &gt; 0.71 kG on the dwarf's magnetic field, and measured a P = 1.912 ± 0.005 hr periodicity, which we concluded to be due to rotational modulation. The luminosity and period we measured are comparable to those of other ultracool dwarfs observed at radio wavelengths. This implies that future megahertz to gigahertz surveys, with increased cadence and improved sensitivity, are likely to detect similar or later-type dwarfs. Our detection of WISE J062309.94-045624.6 makes this dwarf the coolest and latest-type star observed to produce radio emission.

Keywords: Brown dwarfs, Radio astronomy, Magnetospheric radio emissions, T dwarfs
When the Stars Align: A 5σ Concordance of Planetary Nebulae Major Axes in the Center of Our Galaxy. We report observations of a remarkable major axes alignment nearly parallel to the Galactic plane of 5σ significance for a subset of bulge "planetary nebulae" (PNe) that host, or are inferred to host, short-period binaries. Nearly all are bipolar. It is solely this specific PN population that accounts for the much weaker statistical alignments previously reported for the more general bulge PNe. It is clear evidence of a persistent, organized process acting on a measurable parameter at the heart of our galaxy over perhaps cosmologically significant periods of time for this very particular PN sample. Stable magnetic fields are currently the only plausible mechanism that could affect multiple binary star orbits as revealed by the observed major axes orientations of their eventual PNe. Examples are fed into the current bulge PN population at a rate determined by their formation history and mass range of their binary stellar progenitors.

Keywords: Planetary nebulae nuclei, Emission nebulae, Binary stars, Planetary nebulae
Evidence for a Black Hole Spin-Orbit Misalignment in the X-Ray Binary Cyg X-1. Recently, the accretion geometry of the black hole X-ray binary Cyg X-1 was probed with the X-ray polarization. The position angle of the X-ray-emitting flow was found to be aligned with the position angle of the radio jet in the plane of the sky. At the same time, the observed high polarization degree could be obtained only for a high inclination of the X-ray-emitting flow, indicating a misalignment between the binary axis and the black hole spin. The jet, in turn, is believed to be directed by the spin axis; hence, a similar misalignment is expected between the jet and binary axes. We test this hypothesis using very long (up to about 26 yr) multiband radio observations. We find a misalignment of 20°-30°. However, contrary to the earlier expectations, the jet and binary viewing angles are found to be similar, while the misalignment is seen between the position angles of the jet and the binary axis on the plane of the sky. Furthermore, the presence of the misalignment calls into question our understanding of the evolution of this binary system.

Keywords: Galactic radio sources, Relativistic jets, High mass x-ray binary stars, X-ray sources
ALMA Reveals a Stable Rotating Gas Disk in a Paradoxical Low-mass, Ultradusty Galaxy at z = 4.274. We report ALMA detections of [C II] and a dust continuum in Az9, a multiply imaged galaxy behind the Frontier Field cluster MACS J0717.5+3745. The bright [C II] emission line provides a spectroscopic redshift of z = 4.274. This strongly lensed (μ = 7 ± 1) galaxy has an intrinsic stellar mass of only 2 × 109 M ⊙ and a total star formation rate of 26 M ⊙ yr-1 (~80% of which is dust-obscured). Using public magnification maps, we reconstruct the [C II] emission in the source plane to reveal a stable, rotation-dominated disk with V/σ = 5.3, which is &gt;2× higher than predicted from simulations for similarly high-redshift, low-mass galaxies. In the source plane, the [C II] disk has a half-light radius of 1.8 kpc and, along with the dust, is spatially offset from the peak of the stellar light by 1.4 kpc. Az9 is not deficient in [C II]; L [C II]/L IR = 0.0027, consistent with local and high-redshift normal star-forming galaxies. While dust-obscured star formation is expected to dominate in higher-mass galaxies, such a large reservoir of dust and gas in a lower-mass disk galaxy 1.4 Gyr after the Big Bang challenges our picture of early galaxy evolution. Furthermore, the prevalence of such low-mass dusty galaxies has important implications for the selection of the highest-redshift dropout galaxies with JWST. As one of the lowest stellar mass galaxies at z &gt; 4 to be detected in a dust continuum and [C II], Az9 is an excellent laboratory in which to study early dust enrichment in the interstellar medium.

Keywords: Strong gravitational lensing, Galaxy kinematics, Spectral energy distribution, Galaxy evolution, Dust continuum emission, Luminous infrared galaxies
A Comprehensive Simulation of Solar Wind Formation from the Solar Interior: Significant Cross-field Energy Transport by Interchange Reconnection near the Sun. The physical connection between thermal convection in the solar interior and the solar wind remains unclear due to their significant scale separation. Using an extended version of the three-dimensional radiative magnetohydrodynamic code RAMENS, we perform the first comprehensive simulation of the solar wind formation, starting from the wave excitation and the small-scale dynamo below the photosphere. The simulation satisfies various observational constraints as a slow solar wind emanating from the coronal hole boundary. The magnetic energy is persistently released in the simulated corona, showing a hot upward flow at the interface between open and closed fields. To evaluate the energetic contributions from Alfvén wave and interchange reconnection, we develop a new method to quantify the cross-field energy transport in the simulated atmosphere. The measured energy transport from closed coronal loops to open field accounts for approximately half of the total. These findings suggest a significant role of the supergranular-scale interchange reconnection in solar wind formation.

Keywords: Supergranulation, Solar convective zone, Solar wind, Solar corona, Magnetic fields
The First JWST Spectral Energy Distribution of a Y Dwarf. We present the first JWST spectral energy distribution of a Y dwarf. This spectral energy distribution of the Y0 dwarf WISE J035934.06-540154.6 consists of low-resolution (λ/Δλ ~100) spectroscopy from 1-12 μm and three photometric points at 15, 18, and 21 μm. The spectrum exhibits numerous fundamental, overtone, and combination rotational-vibrational bands of H2O, CH4, CO, CO2, and NH3, including the previously unidentified ν 3 band of NH3 at 3 μm. Using a Rayleigh-Jeans tail to account for the flux emerging at wavelengths greater than 21 μm, we measure a bolometric luminosity of 1.523 ± 0.090 × 1020 W. We determine a semiempirical effective temperature estimate of ${467}_{-18}^{+16}$ K using the bolometric luminosity and evolutionary models to estimate a radius. Finally, we compare the spectrum and photometry to a grid of atmospheric models and find reasonably good agreement with a model having T eff = 450 K, log g = 3.25 [cm s-2], and [M/H] = -0.3. However, the low surface gravity implies an extremely low mass of 1 M Jup and a very young age of 20 Myr, the latter of which is inconsistent with simulations of volume-limited samples of cool brown dwarfs.

Keywords: Brown dwarfs, Stellar effective temperatures, Y dwarfs, Spectroscopy, Near infrared astronomy
Core-envelope Decoupling Drives Radial Shear Dynamos in Cool Stars. Differential rotation is thought to be responsible for the dynamo process in stars like our Sun, driving magnetic activity and starspots. We report that starspot measurements in the Praesepe open cluster are strongly enhanced only for stars that depart from standard models of rotational evolution. A decoupling of the spin-down history between the core and envelope explains both the activity and rotation anomalies: surface rotational evolution is stalled by interior angular momentum redistribution, and the resultant radial shears enhance starspot activity. These anomalies provide evidence for an evolving front of shear-enhanced activity affecting the magnetic and rotational evolution of cool stars and the high-energy environments of their planetary companions for hundreds of millions to billions of years on the main sequence.

Keywords: Starspots, Stellar magnetic fields, Stellar activity, Stellar rotation, Stellar evolution