adsabs/SciX_UAT_keywords huggingface dataset:
Ammonia Abundance Derived from Juno MWR and VLA Observations of Jupiter

The vertical distribution of trace gases in planetary atmospheres can be obtained with observations of the atmosphere's thermal emission. Inverting radio observations to recover the atmospheric structure, however, is nontrivial, and the solutions are degenerate. We propose a modeling framework to prescribe a vertical distribution of trace gases that combines a thermochemical equilibrium model with a vertical temperature structure and compare these results to models where ammonia can vary between predefined pressure nodes. We compare these model to nadir brightness temperatures and limb-darkening parameters, together with their uncertainties, which we reduced from the raw Juno Microwave Radiometer (MWR) data set. We then apply this framework to MWR observations during Juno's first years of operation (perijove passes 1-12) and to longitudinally averaged latitude scans taken with the upgraded Very Large Array. We use the model to constrain the distribution of ammonia between -60° and 60° latitude and down to 100 bars. We constrain the ammonia abundance to be ${340.5}_{-21.2}^{+34.8}$ ppm ( ${2.66}_{-0.17}^{+0.27}\times $ solar abundance) and find a depletion of ammonia down to a depth of ~20 bars, which supports the existence of processes that deplete the atmosphere below the ammonia and water cloud layers. At the equator we find an increase of ammonia with altitude, while the zones and belts in the midlatitudes can be traced down to levels where the atmosphere is well mixed. The latitudinal variation in the ammonia abundance appears to be opposite to that shown at higher altitudes, which supports the existence of a stacked-cell circulation model.

Keywords: planetary atmospheres; atmospheric composition; radio astronomy
A Catalog of Nearby Accelerating Star Candidates in Gaia DR3

We describe a new catalog of accelerating star candidates with Gaia G ≤ 17.5 mag and distances d ≤ 100 pc. Designated as the Gaia Nearby Accelerating Star Catalog (GNASC), it contains 29,684 members identified using a supervised machine-learning algorithm trained on the Hipparcos-Gaia Catalog of Accelerations (HGCA), Gaia Data Release 2, and Gaia Early Data Release 3. We take advantage of the difference in observation timelines between the two Gaia catalogs and information about the quality of the astrometric modeling based on the premise that acceleration will correlate with astrometric uncertainties. Catalog membership is based on whether constant proper motion over three decades can be ruled out at high confidence (greater than 99.9%). Test data suggest that catalog members each have a 68% likelihood of true astrometric acceleration; subsets of the catalog perform even better, with the likelihood exceeding 85%. We compare the GNASC with Gaia Data Release 3 and its table of stars for which acceleration is detected at high confidence based on precise astrometric fits. Our catalog, derived without this information, captures over 96% of the sources in the table that meet our selection criteria. In addition, the GNASC contains bright, nearby candidates that were not in the original Hipparcos survey, including members of known binary systems as well as stars with companions yet to be identified. It thus extends the HGCA and demonstrates the potential of the machine-learning approach for discovering hidden partners of nearby stars in future astrometric surveys.

Keywords: binary stars; substellar companion stars; multiple stars
Clustering of Intermittent Magnetic and Flow Structures near Parker Solar Probe's First Perihelion—A Partial-variance-of-increments Analysis

During the Parker Solar Probe's (PSP) first perihelion pass, the spacecraft reached within a heliocentric distance of ∼37 R⊙ and observed numerous magnetic and flow structures characterized by sharp gradients. To better understand these intermittent structures in the young solar wind, an important property to examine is their degree of correlation in time and space. To this end, we use the well-tested partial variance of increments (PVI) technique to identify intermittent events in FIELDS and SWEAP observations of magnetic and proton-velocity fields (respectively) during PSP's first solar encounter, when the spacecraft was within 0.25 au from the Sun. We then examine distributions of waiting times (WT) between events with varying separation and PVI thresholds. We find power-law distributions for WT shorter than a characteristic scale comparable to the correlation time of the fluctuations, suggesting a high degree of correlation that may originate in a clustering process. WT longer than this characteristic time are better described by an exponential, suggesting a random memory-less Poisson process at play. These findings are consistent with near-Earth observations of solar wind turbulence. The present study complements the one by Dudok de Wit et al., which focuses on WT between observed "switchbacks" in the radial magnetic field.

Keywords: interplanetary turbulence; solar wind; interplanetary discontinuities; solar corona; magnetohydrodynamics
Disks of Stars in the Galactic Center Triggered by Tidal Disruption Events

In addition to a supermassive black hole (SMBH), the central parsec of the Milky Way hosts over 100 massive, high-velocity young stars whose existence, and organization of a subset of them in one, or possibly two, misaligned disks, is puzzling. Due to a combination of low medium density and strong tidal forces in the vicinity of Sgr A*, stars are not expected to form. Here we propose a novel scenario for their in situ formation: a jetted tidal disruption event (TDE) from an older wandering star triggers an episode of positive feedback of star formation in the plane perpendicular to the jet, as demonstrated via numerical simulations in the context of jet-induced feedback in galactic outflows. An overpressured cocoon surrounding the jet shock-compresses clumps to densities high enough to resist the SMBH tidal field. The TDE rate of 10-5-10-4 yr-1 per galaxy, out of which a few percent of events are jetted, implies a jetted TDE event per galaxy to occur every few million years. This timescale is interestingly of the same order of the age of the disk stars. The mass function predicted by our mechanism is top heavy. Additionally, since TDEs are isotropic, our model predicts a random orientation for the disk of stars with respect to the plane of the galaxy and, due to the relatively high TDE rate, can account for multiple disks of stars with uncorrelated orientations.

Keywords: supermassive black holes; tidal disruption; star formation
Distributed YSOs in the Perseus Molecular Cloud from the Gaia and LAMOST Surveys

Identifying the young optically visible population in a star-forming region is essential for fully understanding the star formation event. In this paper, we identify 211 candidate members of the Perseus molecular cloud based on Gaia astrometry. We use LAMOST spectra to confirm that 51 of these candidates are new members, bringing the total census of known members to 856. The newly confirmed members are less extincted than previously known members. Two new stellar aggregates are identified in our updated census. With the updated member list, we obtain a statistically significant distance gradient of 4.84 pc deg-1 from west to east. Distances and extinction corrected color-magnitude diagrams indicate that NGC 1333 is significantly younger than IC 348 and the remaining cloud regions. The disk fraction in NGC 1333 is higher than elsewhere, consistent with its youngest age. The star formation scenario in the Perseus molecular cloud is investigated and the bulk motion of the distributed population is consistent with the cloud being swept away by the Per-Tau Shell.

Keywords: pre-main sequence stars; spectroscopy; statistical parallax; hertzsprung russell diagram; two-color diagrams; star forming regions; proper motions
Remnant Black Hole Kicks and Implications for Hierarchical Mergers

When binary black holes merge in dense star clusters, their remnants can pair up with other black holes in the cluster, forming heavier and heavier black holes in a process called hierarchical merger. The most important condition for hierarchical merger to occur is that remnants formed by mergers are retained by the host star cluster. Using the publicly available gravitational-wave event database, we infer the magnitudes of kick velocities imparted to the remnant black holes due to anisotropic emission of gravitational waves and use that to quantify the retention probability of each event as a function of the escape speed of the star cluster. Among the second gravitational-wave transient catalog (GWTC-2) events, GW190814 provides the tightest constraint on the kick magnitude with ${V}_{\mathrm{kick}}={74}_{-7}^{+10}$ km s-1 at the 90% credible level. We find that star clusters with escape speeds of 200 km s-1 can retain about 50% of the events in the GWTC-2. Using the escape speed distributions of nuclear star clusters and globular clusters, we find that ~17 (2) remnants of GWTC-2 may be retained by the host star cluster if all GWTC-2 events occurred in nuclear (globular) clusters. Our study demonstrates the importance of folding in kick velocity inferences in future studies of hierarchical mergers.

Keywords: gravitational waves; astrophysical black holes; high energy astrophysics; star clusters
ZWCL 1856.8: A Rare Double Radio Relic System Captured within NuSTAR and Chandra Field of View

Observations of galaxy cluster mergers provide insights on the particle acceleration and heating mechanisms taking place within the intracluster medium. Mergers form shocks that propagate through the plasma, which result in shock/cold fronts in the X-ray, and radio halos and/or relics in the radio regime. The connection between these tracers and the mechanisms driving non-thermal processes, such as inverse Compton, are not well understood. ZWCL 1856.8 is one of the few known double radio relic systems that originate from nearly head-on collisions observed close to the plane of the sky. For the first time, we study NuSTAR and Chandra observations of this system, which contains both relics within their field of view. The spectro-imaging analyses results of the system suggest weak shock fronts with ${ \mathcal M }$ numbers within 2σ of the radio-derived values, and provide evidence of inverse Compton emission at both relic sites. Our findings have great uncertainties due to the shallow exposure times available. Deeper NuSTAR and Chandra data are crucial for studying the connection of the radio and X-ray emission features and for constraining the thermal versus non-thermal emission contributions in this system. We also present methods and approaches on how to investigate X-ray properties of double relic systems by taking full advantage of the complementary properties of NuSTAR and Chandra missions.

Keywords: galaxy clusters; high energy astrophysics; non-thermal radiation sources; shocks
The Optical Two- and Three-dimensional Fundamental Plane Correlations for Nearly 180 Gamma-Ray Burst Afterglows with Swift/UVOT, RATIR, and the Subaru Telescope

Gamma-ray bursts (GRBs) are fascinating events due to their panchromatic nature. We study optical plateaus in GRB afterglows via an extended search into archival data. We comprehensively analyze all published GRBs with known redshifts and optical plateaus observed by many ground-based telescopes (e.g., Subaru Telescope, RATIR) around the world and several space-based observatories such as the Neil Gehrels Swift Observatory. We fit 500 optical light curves, showing the existence of the plateau in 179 cases. This sample is 75% larger than the previous one, and it is the largest compilation so far of optical plateaus. We discover the 3D fundamental plane relation at optical wavelengths using this sample. This correlation is between the rest-frame time at the end of the plateau emission, ${T}_{\mathrm{opt}}^{* }$ , its optical luminosity, L opt, and the peak in the optical prompt emission, L peak,opt, thus resembling the three-dimensional (3D) X-ray fundamental plane (the so-called 3D Dainotti relation). We correct our sample for redshift evolution and selection effects, discovering that this correlation is indeed intrinsic to GRB physics. We investigate the rest-frame end-time distributions in X-rays and optical ( ${T}_{\mathrm{opt}}^{* }$ , ${T}_{{\rm{X}}}^{* }$ ), and conclude that the plateau is achromatic only when selection biases are not considered. We also investigate if the 3D optical correlation may be a new discriminant between optical GRB classes and find that there is no significant separation between the classes compared to the Gold sample plane after correcting for evolution.

Keywords: gamma-ray bursts
The GMRT High Resolution Southern Sky Survey for Pulsars and Transients. VI. Discovery of Nulling, Localization, and Timing of PSR J1244-4708

Many pulsars in the known population exhibit nulling, which is characterized by a sudden cessation and subsequent restoration of radio emission. In this work, we present the localization, timing, and emission properties of a pulsar discovered by the GMRT High Resolution Southern Sky survey: J1244-4708. Moreover, we find that this pulsar shows nulling, with a nulling fraction close to 60%. A quasiperiodicity is also seen in the nulling from this pulsar with two timescales. We demonstrate the broadband nature of nulling in this pulsar using simultaneous observations in band-3 (300-500 MHz) and band-4 (550-750 MHz) with the upgraded GMRT. We also present a comparison of the efficiency of various search approaches such as single pulse search, fast folding algorithm (FFA)-based search, and fast Fourier transform-based search to search for nulling pulsars. We demonstrated that the FFA search is advantageous for detecting extreme nulling pulsars, which is also confirmed with multiple epochs of observations for the nulling pulsars using the GMRT.

Keywords: radio pulsars; observational astronomy; astronomical techniques
The New Magnetar SGR J1830-0645 in Outburst

The detection of a short hard X-ray burst and an associated bright soft X-ray source by the Swift satellite in 2020 October heralded a new magnetar in outburst, SGR J1830-0645. Pulsations at a period of ∼10.4 s were detected in prompt follow-up X-ray observations. We present here the analysis of the Swift/Burst Alert Telescope burst, of XMM-Newton and the Nuclear Spectroscopic Telescope Array observations performed at the outburst peak, and of a Swift/X-ray Telescope monitoring campaign over the subsequent month. The burst was single-peaked, lasted ∼6 ms, and released a fluence of ≈5 × 10-9 erg cm-2 (15-50 keV). The spectrum of the X-ray source at the outburst peak was well described by an absorbed double-blackbody model plus a power-law component detectable up to ∼25 keV. The unabsorbed X-ray flux decreased from ∼5 × 10-11 to ∼2.5 × 10-11 erg cm-2 s-1 one month later (0.3-10 keV). Based on our timing analysis, we estimate a dipolar magnetic field ≈5.5 × 1014 G at pole, a spin-down luminosity ≈2.4 × 1032 erg s-1, and a characteristic age ≈24 kyr. The spin modulation pattern appears highly pulsed in the soft X-ray band, and becomes smoother at higher energies. Several short X-ray bursts were detected during our campaign. No evidence for periodic or single-pulse emission was found at radio frequencies in observations performed with the Sardinia Radio Telescope and Parkes. According to magneto-thermal evolutionary models, the real age of SGR J1830-0645 is close to the characteristic age, and the dipolar magnetic field at birth was slightly larger, ∼1015 G.

Keywords: magnetars; pulsars; x-ray transient sources; x-ray bursts; magnetic fields; x-ray point sources
Line Formation of Raman-scattered He II λ 4851 in an Expanding Spherical H I Shell in Young Planetary Nebulae

We investigate line formation of Raman-scattered He II at 4851 Å in an expanding neutral, spherical shell that surrounds a point-like He II source located at the center. A new grid-based Monte Carlo code is used to take into consideration the H I density variation along each photon path. In the case of a monochromatic He II emission source, the resultant line profiles are characterized by an asymmetric double-peak structure with a tertiary peak and a significant red tail that may extend to the line centers of He IIλ4859 and Hβ. The peak separation corresponds to the expansion velocity, which we consider is in the range 20-40 km s-1 in this work. Tertiary red peaks are formed as a result of multiple Rayleigh reflections at the inner surface of a hollow, spherical shell of H I. Due to a sharp increase of scattering cross section near resonance, the overall Raman conversion efficiency is significantly enhanced as the expansion speed increases. In the case of a He II line source with a Gaussian line profile with an FWHM of 30-70 km s-1, we obtain distorted redward profiles that are due to the increasing redward cross section of H I. A simple application to the young planetary nebula IC 5117 is consistent with a neutral shell expanding with a speed ∼30 km s-1.

Keywords: planetary nebulae; radiative transfer; stellar mass loss
Gap Opening and Inner Disk Structure in the Strongly Accreting Transition Disk of DM Tau

Large inner dust gaps in transition disks are frequently posited as evidence of giant planets sculpting gas and dust in the disk, or the opening of a gap by photoevaporative winds. Although the former hypothesis is strongly supported by the observations of planets and deep depletions in gas within the gap in some disks, many T Tauri stars hosting transition disks accrete at rates typical for an undepleted disk, raising the question of how gap opening occurs in these objects. We thus present an analysis of the structure of the transition disk around the T Tauri star DM Tau, which is strongly accreting (~10-8.3 M ⊙ yr-1) and turbulent (α = 0.078 ± 0.02). Using the Dust And LInes thermochemical code, we fit disk models to simultaneously reproduce the accretion rate, high level of turbulence, the gas traced by ALMA Band 6 observations of 12CO, 13CO, and C18O J = 2-1 lines, and the observed dust emission from the millimeter continuum and spectral energy distribution. We find a shallow depletion in gas surface density of ~10 relative to the outer disk and a gas-rich inner disk that is consistent with the observations. The planet mass of <1 M Jup implied by the gap depth is in tension with predictions for dust trapping in a highly viscous disk, which requires a more massive planet of ~10 M Jup. Photoevaporative models including a dead zone can qualitatively reproduce some features of the DM Tau disk, but still struggle to explain the high accretion rates and the observed millimeter-continuum flux.

Keywords: protoplanetary disks; planetary system formation; stellar accretion disks; star formation; planet formation; astrochemistry; planetary-disk interactions; millimeter astronomy
The Science Case for Spacecraft Exploration of the Uranian Satellites: Candidate Ocean Worlds in an Ice Giant System

The 27 satellites of Uranus are enigmatic, with dark surfaces coated by material that could be rich in organics. Voyager 2 imaged the southern hemispheres of Uranus's five largest "classical" moons-Miranda, Ariel, Umbriel, Titania, and Oberon, as well as the largest ring moon, Puck-but their northern hemispheres were largely unobservable at the time of the flyby and were not imaged. Additionally, no spatially resolved data sets exist for the other 21 known moons, and their surface properties are essentially unknown. Because Voyager 2 was not equipped with a near-infrared mapping spectrometer, our knowledge of the Uranian moons' surface compositions, and the processes that modify them, is limited to disk-integrated data sets collected by ground- and space-based telescopes. Nevertheless, images collected by the Imaging Science System on Voyager 2 and reflectance spectra collected by telescope facilities indicate that the five classical moons are candidate ocean worlds that might currently have, or had, liquid subsurface layers beneath their icy surfaces. To determine whether these moons are ocean worlds, and to investigate Uranus's ring moons and irregular satellites, close-up observations and measurements made by instruments on board a Uranus orbiter are needed.

Keywords: uranian satellites; planetary surfaces; planetary structure; surface composition
Galaxy Quenching with Mass Growth History of Galaxy Groups and Clusters: The Importance of Post-processing

We investigate the fraction of quenched satellite galaxies in host galaxy groups and clusters using TNG300 in the IllustrisTNG cosmological magnetohydrodynamical simulations. The simulations show that most satellites are quenched after they fall into their final hosts, and that post-processing is a more dominant mechanism of galaxy quenching than pre-processing. We find that the fraction of quenched satellites at z = 0 increases with host mass, which implies that more massive hosts have higher quenching efficiency because they have more massive groups infalling. Furthermore, we find that hosts that have many early-infall satellites show a higher fraction of quenched satellites at z = 0 than those that have many late-infall satellites, which results in a scatter of the quenched fraction of satellites in a given mass range of hosts at z = 0. Our results highlight the significance of the mass of hosts and the different infall times of satellites in understanding galaxy quenching.

Keywords: galaxy quenching; galaxy evolution; galaxy clusters; galaxy groups; red sequence galaxies; astronomical simulations
Spectroscopy of the Proposed White Dwarf Pulsar ASASSN-V J205543.90+240033.5

We obtained spectra of ASASSN-V J205543.90+240033.5 (J2055), a system that shows photometric variations similar to the white dwarf (WD) pulsar AR Scorpii. Our spectra display a continuum rising steeply toward the blue as well as an array of emission lines. Resolved Balmer and Paschen lines are seen with Hα and Hβ having central absorption features. The strongest lines are unresolved C II, C III, and N III as well as doubly ionized helium. The spectra are similar to that of YY Hya, and suggest that J2055 is a post-common envelope binary consisting of a hot compact star irradiating the face of a secondary of unknown spectral type. Velocity variations detected from the emission lines confirm the binary nature of J2055. The origin of the 10 minutes photometric variation remains uncertain.

Keywords: variable stars; close binary stars; common envelope evolution; white dwarf stars