Sazuna/UAT_keywords huggingface dataset:
Where are the Water Worlds?: Self-consistent Models of Water-rich Exoplanet Atmospheres. It remains to be ascertained whether sub-Neptune exoplanets primarily possess hydrogen-rich atmospheres or whether a population of H2O-rich water worlds lurks in their midst. Addressing this question requires improved modeling of water-rich exoplanetary atmospheres, both to predict and interpret spectroscopic observations and to serve as upper boundary conditions on interior structure calculations. Here, we present new models of hydrogen-helium-water atmospheres with water abundances ranging from solar to 100% water vapor. We improve upon previous models of high-water-content atmospheres by incorporating updated prescriptions for water self-broadening and a nonideal gas equation of state. Our model grid (https://umd.box.com/v/water-worlds) includes temperature–pressure profiles in radiative-convective equilibrium, along with their associated transmission and thermal emission spectra. We find that our model updates primarily act at high pressures, significantly impacting bottom-of-atmosphere temperatures, with implications for the accuracy of interior structure calculations. Upper-atmosphere conditions and spectroscopic observables are less impacted by our model updates, and we find that, under most conditions, retrieval codes built for hot Jupiters should also perform well on water-rich planets. We additionally quantify the observational degeneracies among both thermal emission and transmission spectra. We recover standard degeneracies with clouds and mean molecular weight for transmission spectra, and we find thermal emission spectra to be more readily distinguishable from one another in the water-poor (i.e., near-solar) regime.

Keywords: Exoplanets, Exoplanet astronomy, Radiative transfer, Mini Neptunes, Exoplanet atmospheres
Constraints on the Cosmological Parameters with Three-Parameter Correlation of Gamma-Ray Bursts. As one of the most energetic and brightest events, gamma-ray bursts (GRBs) can be treated as a promising probe of the high-redshift universe. Similar to type Ia supernovae, GRBs with the same physical origin could be treated as standard candles. We select GRB samples with the same physical origin, which are divided into two groups. The first group consists of 31 GRBs with a plateau phase feature of a constant luminosity followed by a decay index of about -2 in the X-ray afterglow light curves, and the second group has 50 GRBs with a shallow decay phase in the optical light curves. For the selected GRB samples, we confirm that there is a tight correlation between the plateau luminosity L 0, the end time of plateau t  b , and the isotropic energy release E  γ,iso. We also find that the L 0-t  b  - E  γ,iso correlation is insensitive to the cosmological parameters and that no valid limitations on the cosmological parameters can be obtained using this correlation. We explore a new three-parameter correlation L 0, t  b , and the spectral peak energy in the rest-frame E  p,i  (L 0-t  b -E  p,i ), and find that this correlation can be used as a standard candle to constrain the cosmological parameters. By employing the optical sample only, we find the constraints of ${{\rm{\Omega }}}_{m}={0.697}_{-0.278}^{+0.402}(1\sigma )$ for a flat ΛCDM model. For the non-flat ΛCDM model, the best-fitting results are ${{\rm{\Omega }}}_{m}={0.713}_{-0.278}^{+0.346}$ , ${{\rm{\Omega }}}_{{\rm{\Lambda }}}={0.981}_{-0.580}^{+0.379}(1\sigma )$ . For the combination of the X-ray and optical samples, we find ${{\rm{\Omega }}}_{m}={0.313}_{-0.125}^{+0.179}(1\sigma )$ for a flat ΛCDM model, and ${{\rm{\Omega }}}_{m}={0.344}_{-0.112}^{+0.176}$ , ${{\rm{\Omega }}}_{{\rm{\Lambda }}}={0.770}_{-0.416}^{+0.366}(1\sigma )$ for a non-flat ΛCDM model.

Keywords: Magnetars, Gamma-ray bursters, Cosmological parameters
Gas Sources from the Coma and Nucleus of Comet 46P/Wirtanen Observed Using ALMA. Gas-phase molecules in cometary atmospheres (comae) originate primarily from (1) outgassing by the nucleus, (2) sublimation of icy grains in the near-nucleus coma, and (3) coma (photo)chemical processes. However, the majority of cometary gases observed at radio wavelengths have yet to be mapped, so their production/release mechanisms remain uncertain. Here we present observations of six molecular species toward comet 46P/Wirtanen, obtained using the Atacama Large Millimeter/submillimeter Array during the comet's unusually close (~0.1 au) approach to Earth in 2018 December. Interferometric maps of HCN, CH3OH, CH3CN, H2CO, CS, and HNC were obtained at an unprecedented sky-projected spatial resolution of up to 25 km, enabling the nucleus and coma sources of these molecules to be accurately quantified. The HCN, CH3OH, and CH3CN spatial distributions are consistent with production by direct outgassing from (or very close to) the nucleus, with a significant proportion of the observed CH3OH originating from sublimation of icy grains in the near-nucleus coma (at a scale length L  p  = 36 ± 7 km). On the other hand, H2CO, CS, and HNC originate primarily from distributed coma sources (with L  p  values in the range 550-16,000 km), the identities of which remain to be established. The HCN, CH3OH, and HNC abundances in 46P are consistent with the average values previously observed in comets, whereas the H2CO, CH3CN, and CS abundances are relatively low.

Keywords: Interstellar molecules, High resolution spectroscopy, Short period comets, Molecular spectroscopy, Millimeter-wave spectroscopy, Radiative transfer, Radio interferometry, Comet volatiles
On Secular Gravitational Instability in Vertically Stratified Disks. Secular gravitational instability (GI) is one promising mechanism for explaining planetesimal formation. Previous studies of secular GI utilized a razor-thin disk model and derived the growth condition in terms of vertically integrated physical values such as dust-to-gas surface density ratio. However, in weakly turbulent disks where secular GI can operate, a dust disk can be orders of magnitude thinner than a gas disk, and analyses treating the vertical structures are necessary to clarify the interplay of the midplane dust motion and the upper gas motion. In this work, we perform vertically global linear analyses of secular GI with a vertical domain size of a few gas scale heights. We find that dust grains accumulate radially around the midplane while gas circulates over the whole vertical region. We obtain well-converged growth rates when the outer gas boundary is above two gas scale heights. The growth rates are underestimated if we assume the upper gas to be steady and regard it just as the source of external pressure to the dusty lower layer. Therefore, treating the upper gas motion is important even when the dust disk is much thinner than the gas disk. Conducting a parameter survey, we represent the growth condition in terms of the Toomre Q value for dust and dust-to-gas surface density ratio. The critical dust disk mass for secular GI is ~10-4 M * for a dust-to-gas surface density ratio of 0.01, a Stokes number of 0.1, and a radial dust diffusivity of 10-4 c s H, where c s is the gas sound speed, and H is the gas scale height.

Keywords: Astrophysical fluid dynamics, Protoplanetary disks, Hydrodynamics
Probing the Origin of Changing-look Quasar Transitions with Chandra. Extremely variable quasars can also show strong changes in broad-line emission strength and are known as changing-look quasars (CLQs). To study the CLQ transition mechanism, we present a pilot sample of CLQs with X-ray observations in both the bright and faint states. From a sample of quasars with bright-state archival SDSS spectra and (Chandra or XMM-Newton) X-ray data, we identified five new CLQs via optical spectroscopic follow-up and then obtained new target-of-opportunity X-ray observations with Chandra. No strong absorption is detected in either the bright- or the faint-state X-ray spectra. The intrinsic X-ray flux generally changes along with the optical variability, and the X-ray power-law slope becomes harder in the faint state. Large-amplitude mid-infrared variability is detected in all five CLQs, and it echoes the variability in the optical with a time lag expected from the light-crossing time of the dusty torus for CLQs with robust lag measurements. The changing-obscuration model is not consistent with the observed X-ray spectra and spectral energy distribution changes seen in these CLQs. It is highly likely that the observed changes are due to the changing accretion rate of the supermassive black hole, so the multiwavelength emission varies accordingly, with promising analogies to the accretion states of X-ray binaries.

Keywords: Accretion, Variable radiation sources, Quasars, Active galactic nuclei, Catalogs
Multiple Stellar Populations in Metal-poor Globular Clusters with JWST: A NIRCam View of M92. Recent work on metal-intermediate globular clusters (GCs) with [Fe/H] = -1.5 and -0.75 has illustrated the theoretical behavior of multiple populations in photometric diagrams obtained with the JWST. These results are confirmed by observations of multiple populations among the M dwarfs of 47 Tucanae. Here we explore multiple populations in metal-poor GCs with [Fe/H] = -2.3. We take advantage of synthetic spectra and isochrones that account for the chemical composition of multiple populations to identify photometric diagrams that separate the distinct stellar populations of GCs. We derive high-precision photometry and proper motion for main-sequence (MS) stars in the metal-poor GC M92 from JWST and Hubble Space Telescope images. We identify a first-generation (1G) and two main groups of second-generation (2GA and 2GB) stars and investigate their kinematics and chemical composition. We find isotropic motions with no differences among the distinct populations. The comparison between the observed colors of the M92 stars and the colors derived by synthetic spectra reveals that the helium abundances of 2GA and 2GB stars are higher than those of the 1G by ΔY ~ 0.01 and 0.04, respectively. The m F090W versus m F090W - m F277W color-magnitude diagram shows that below the knee MS stars exhibit a wide color broadening due to multiple populations. We constrain the amount of oxygen variation needed to reproduce the observed MS width, which is consistent with results on red giant branch stars. We conclude that multiple populations with masses of ~0.1-0.8 M ⊙ share similar chemical compositions.

Keywords: Globular star clusters, Population II stars, Stellar abundances, Photometry
Orbital Period Variations in HT Cas: Evidence for Additional Angular Momentum Loss and a High-eccentricity Giant Planet. We present a timing study of the short-period eclipsing cataclysmic variable (CV) HT Cas. Based on new eclipse times derived from our photometric monitoring and archival optical data, combined with historical timings, spanning ~42 yr, we detect a secular decrease in the orbital period at a rate of $\dot{P}=-1.32\times {10}^{-12}\,{\mathrm{ss}}^{-1}$ and a cyclic period wiggle with an amplitude of 79.3 s and a period of 30.28 yr. We find that neither gravitational radiation nor magnetic braking can explain the observed decrease rate, suggesting the presence of additional angular momentum loss (AML). The empirical consequential AML (eCAML) model developed by Schreiber et al. can well match the observed orbital decay in HT Cas, and the physical mechanism for eCAML is most likely attributable to the frictional AML following nova eruptions. As for the cyclic variation, the best explanation is the influence of an unseen companion in orbit around the binary. The derived orbital parameters reveal that the hypothetical third body could be a giant planet with mass of M 3 ≃ 14M Jup that is moving on a highly eccentric orbit (e = 0.82). Taken together the results of the present study suggest that HT Cas is a unique triple system containing a high-eccentricity giant planet and it has the potential to become an ideal laboratory in which to test models of CV evolution.

Keywords: Close binary stars, Cataclysmic variable stars, Eclipsing binary stars, Dwarf novae
On the Effects of Local Environment on Active Galactic Nucleus (AGN) in the Horizon Run 5 Simulation. We use the Horizon Run 5 cosmological simulation to study the effect of galaxy intrinsic properties and the local environment on active galactic nuclei (AGNs) characterized by their threshold of the accretion rate. We select galaxies in the stellar mass range ${10}^{9.5}\leqslant {M}_{* }^{}/{M}_{\odot }^{}\leqslant {10}^{10.5}$ in the snapshot at redshift z = 0.625. Among various intrinsic properties, we find that the star formation rate of the host galaxy is most correlated to the AGN activity. To quantify the environment, we use background galaxy number density (large-scale environment) and distance and morphological type of the nearest neighbors (small-scale environment), and study their relative effects on the AGN properties. We find that, compared to the background density, the nearest neighbor environment is the dominant quantity determining the bolometric luminosity, star formation rate, and kinematic properties of AGNs and better dictates the gas mass of the host galaxy. We show that the cold gas content in the host galaxies is crucial in triggering AGN activity. However, when the nearest neighbor environment effects start to act at the neighbor distance of less than about half the virial radius of the neighbor, the neighbor environmental effects are the most dominant factor for quasar activity.

Keywords: AGN host galaxies, Galaxy encounters, Galaxy interactions, Galaxy environments
Fine Structures of Radio Bursts from Flare Star AD Leo with FAST Observations. Radio bursts from nearby active M-dwarfs have been frequently reported and extensively studied in solar or planetary paradigms. Whereas, their substructures or fine structures remain rarely explored despite their potential significance in diagnosing the plasma and magnetic field properties of the star. Such studies in the past have been limited by the sensitivity of radio telescopes. Here we report the inspiring results from the high time-resolution observations of a known flare star AD Leo with the Five-hundred-meter Aperture Spherical radio Telescope. We detected many radio bursts in the 2 days of observations with fine structures in the form of numerous millisecond-scale sub-bursts. Sub-bursts on the first day display stripe-like shapes with nearly uniform frequency drift rates, which are possibly stellar analogs to Jovian S-bursts. Sub-bursts on the second day, however, reveal a different blob-like shape with random occurrence patterns and are akin to solar radio spikes. The new observational results suggest that the intense emission from AD Leo is driven by electron cyclotron maser instability, which may be related to stellar flares or interactions with a planetary companion.

Keywords: Stellar magnetic fields, Flare stars, Radio bursts, Stellar flares, Star-planet interactions
B-fields and Dust in Interstellar Filaments Using Dust Polarization (BALLAD-POL). I. The Massive Filament G11.11-0.12 Observed by SOFIA/HAWC+. We report the first measurement of polarized thermal dust emission toward the entire infrared dark cloud G11.11-0.12 taken by the polarimeter SOFIA/HAWC+ at 214 μm. The obtained magnetic fields (B-fields) from the polarized emission of the early-stage and massive filament tend to be perpendicular to its spine. We produce a map of B-field strengths for the center region of the filament. The strengths vary in the range of 100-600 μG and are strongest along the filament's spine. The central region is sub-Alfvénic and mostly subcritical, meaning that B-fields dominate over turbulence and are strong enough to resist gravitational collapse. The alignment and properties of dust grains in the filament are studied using radiative torque (RAT) theory. We find the decrease of polarization degree P with emission intensity I, i.e., depolarization effect, of the form P ∝ I -α  with α ~ 0.8-0.9, implying a significant loss of grain alignment in the filament's spine. The depolarization can be explained by the decrease in RAT alignment efficiency toward the denser regions with weaker radiation field, which cannot be explained by B-field tangling. We study the effect of the enhanced magnetic relaxation by embedded iron inclusions on RAT alignment and find that the high polarization fraction P ~ 20%-30% in the outer layer of the filament is potential evidence for the magnetically enhanced RAT alignment mechanism. This is the first time this effect is evaluated in a filament. Based on the polarization fraction and RAT alignment theory, we also find evidence for grain growth in the filament.

Keywords: Interstellar dust, Interstellar filaments, Star forming regions, Far infrared astronomy, Interstellar magnetic fields, Star formation, Interstellar medium
Reanalysis of the X-Ray-burst-associated FRB 200428 with Insight-HXMT Observations. A double-peak X-ray burst from the Galactic magnetar SGR J1935+2154 was discovered to be associated with the two radio pulses of FRB 200428 separated by 28.97 ± 0.02 ms. Precise measurements of the timing and spectral properties of the X-ray bursts are helpful for understanding the physical origin of fast radio bursts. In this paper, we have reconstructed some information about the hard X-ray events, which were lost because the High Energy X-ray Telescope (HE) on board the Insight-HXMT mission was saturated by this extremely bright burst, and used the information to improve the temporal and spectral analyses of the X-ray burst. The arrival times of the two X-ray peaks by fitting the new Insight-HXMT/HE lightcurve with multi-Gaussian profiles are 2.77 ± 0.45 ms and 34.30 ± 0.56 ms after the first peak of FRB 200428, respectively, while these two parameters are 2.57 ± 0.52 ms and 32.5 ± 1.4 ms if the fitting profile is a fast-rise and exponential decay function. The spectrum of the two X-ray peaks could be described by a cutoff power law with cutoff energy ~60 keV and photon index ~1.4; the latter is softer than the result obtained in Li et al. when the two X-ray peaks appeared.

Keywords: Magnetars, X-ray bursts, Radio transient sources
Full Velocities and Propagation Directions of Coronal Mass Ejections Inferred from Simultaneous Full-disk Imaging and Sun-as-a-star Spectroscopic Observations. Coronal mass ejections (CMEs) are violent ejections of magnetized plasma from the Sun that can trigger geomagnetic storms, endanger satellite operations, and destroy electrical infrastructures on the Earth. After systematically searching Sun-as-a-star spectra observed by the Extreme Ultraviolet Variability Experiment on board the Solar Dynamics Observatory (SDO) from 2010 May to 2022 May, we identified eight CMEs associated with flares and filament eruptions by analyzing the blue-wing asymmetry of the O III 52.58 nm line profiles. Combined with images simultaneously taken by the 30.4 nm channel of the Atmospheric Imaging Assembly on board SDO, the full velocity and propagation direction for each of the eight CMEs are derived. We find a strong correlation between geomagnetic indices (Kp and Dst) and the angle between the CME propagation direction and the Sun-Earth line, suggesting that Sun-as-a-star spectroscopic observations at extreme-ultraviolet wavelengths can potentially help to improve the prediction accuracy of the geoeffectiveness of CMEs. Moreover, an analysis of synthesized long-exposure Sun-as-a-star spectra implies that it is possible to detect CMEs from other stars through blue-wing asymmetries or blueshifts of spectral lines.

Keywords: Space weather, Stellar coronal mass ejections, Solar filament eruptions, Solar coronal mass ejections, Spectroscopy
High-resolution Observations of Plume Footpoints in a Solar Coronal Hole. Plumes are bright structures in coronal holes extending from the solar surface into the corona and are considered as a possible source of the solar wind. Plumes are thought to be rooted in strong unipolar photospheric flux patches (network/plage region). The magnetic activities at the base of plumes may play a crucial role in producing outflows and propagating disturbances (PDs). However, the role of photospheric/chromospheric activities (e.g., jets/spicules) at the base of plumes and their connection to PDs is poorly understood. Using high-resolution observations of a plume taken on 2020 July 23 with the 1.6 m Goode Solar Telescope (GST), Interface Region Imaging Spectrograph (IRIS), and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, we analyzed chromospheric/transition region activities at the base of the plume and their connection to outflows/PDs in the plume. The GST Visible Imaging Spectrometer images reveal repetitive spicules with blueshifted emission (pseudo-Doppler maps) at the plume's footpoint. In addition, the photospheric magnetograms provide evidence of mixed polarities at the base of the plume. The IRIS Mg II k Dopplergrams show strong blueshifted emission (~50 km s-1) and a high brightness temperature (Mg II k2 line) at the footpoint of the plume. The long-period PDs (P ≈ 20-25 minutes) along the plume (AIA 171 Å) match the periodicity of spicules in the chromospheric images, suggesting a close connection between the spicules and the PDs. We suggest that the interchange reconnection between the closed and open flux of the coronal bright point at the plume's footpoint is the most likely candidate to produce upflows and associated PDs along the plume.

Keywords: Solar coronal plumes
Impact of Changing Stellar and Planetary Magnetic Fields on (Exo)planetary Environments and Atmospheric Mass Loss. The magnetic activity of a star-which modulates the stellar wind outflow-shapes the immediate environments of orbiting (exo)planets and induces atmospheric loss, thereby impacting their habitability. We perform a detailed parameter space study using three-dimensional magnetohydrodynamic simulations to understand the effect of changing stellar wind magnetic field and planetary magnetic field strengths on planetary magnetospheric topology and atmospheric losses. It is observed that the relative strengths of stellar and planetary magnetic fields play a significant role in determining the steady-state magnetospheric configuration and atmospheric erosion. When the stellar field is strengthened or the planetary field is weakened, stellar magnetic field accumulation occurs at the dayside of the planet, forcing the magnetopause to shift closer to its surface. The magnetotail opens up, leading to the formation of Alfvén wings in the nightside wake region. We demonstrate how reconnection processes and wind conditions lead to the bifurcation of the magnetotail current sheet. With increasing stellar wind magnetic field strength, the dayside reconnection point approaches the planet, thereby enhancing mass loss. We establish an analytic equation relating the atmospheric mass-loss rates to stellar and planetary magnetic field strengths, which successfully explains the modeled behavior. Our results are relevant for understanding how the interplay of stellar and planetary magnetism influence (exo)planetary environments and their habitability in star-planet systems with differing relative magnetic field strengths or in a single star-planet system over the course of their evolution with age.

Keywords: Magnetohydrodynamics, Stellar winds, Star-planet interactions, Planetary magnetospheres, Exoplanet atmospheres, Exoplanet atmospheric structure