adsabs/SciX_UAT_keywords huggingface dataset:
Visit Nearby Halo Substructures Using LAMOST DR9 MRS Data

Based on the LAMOST DR9 Medium Resolution Spectra (MRS) catalog, combined with astrometries from Gaia DR3, we conducted an investigation into the substructures in the stellar halo to obtain their chemical and kinematic information. We employed the HDBSCAN algorithm in the (L z , E, L xy ) space for clustering and utilized Mahalanobis distance to merge the clustering results. Ultimately, within the LAMOST DR9 MRS catalog, we identified members of Gaia–Sausage–Enceladus (GSE), Helmi streams, and the high-α disk and in situ halo. Additionally, there are three clusters that cannot be correlated with known substructures. Based on their angular momentum (L z ) characteristics, we have tentatively named two of them High-L z -Cluster-1 (HLC-1) and High-L z -Cluster-2 (HLC-2), both exhibiting high angular momentum (L z ) features. The third cluster, owing to its extremely low L z , is termed the Low-L z -Cluster. Then detailed analysis about those substructures are executed including member stars' identification and kinematic and chemical distribution. The resulting GSE member stars exhibit a well-defined metallicity distribution function with its peak at [Fe/H] ∼ ‑1.2, consistent with previous findings, and we found there appear to be some differences in the distribution on the V total–r gal plane between GSE and its included Splash component. Regarding Helmi streams, in the [Mg/Fe]–[Fe/H] plane we detected potential traces of the α-knee phenomenon at [Fe/H] ∼ ‑1.53. Finally, we tentatively provide the possible origin for the HLC-1 and HLC-2.

Keywords: galaxy kinematics; galaxy structure; galaxy stellar halos; galaxy dynamics
Mach and Froude Numbers on Mars

Mars atmospheric global circulation models exhibit transonic jet streaks during northern winter, which motivates this study of the Mach number, Ma (the ratio of flow speed to the speed of sound), and Froude number, Fr (the ratio of flow speed to the speed of buoyancy waves), as a function of season and location. Two global reanalyses spanning Mars Years (MY) 24 to 32 are used as input, EMARS and OpenMARS. The study's vertical coordinate is potential temperature, θ, ranging from θ = 400 to 1100 K (from z ≈ 32 to 66 km); the floor is set to the lowest level that avoids intersecting mountains. Area-weighted global means and standard deviations and 5 yr temporal means using the complete years MY 25, 26, 29, 30, and 31 are compared. EMARS and OpenMARS show general agreement below θ = 700 K (z ≈ 53 km), where the observational constraints are strongest, but can vary significantly at higher levels. Both reanalyses contain transonic jet streaks in every northern winter sampled. The Fr signal is roughly twice the Ma number signal, as expected where the temperature lapse rate is small compared to the dry adiabatic lapse rate. Mach numbers are similar in both reanalyses but show larger year-to-year variability in OpenMARS. Maps of standard deviations indicate a depression between the main peaks in Tharsis and higher variability in Mare Boreum than Mare Australe. The main conclusion is that the atmosphere of Mars routinely operates in the compressible regime (0.3 < Ma < 0.8), unlike Earth. Aspects of all flow-speed meteorology are discussed.

Keywords: mars; planetary atmospheres; jets
Near-ultraviolet Transmission Spectroscopy of HD 209458b: Evidence of Ionized Iron Beyond the Planetary Roche Lobe

The inflated transiting hot Jupiter HD 209458b is one of the best studied objects since the beginning of exoplanet characterization. Transmission observations of this system between the mid-infrared and the far-ultraviolet have revealed the signature of atomic, molecular, and possibly aerosol species in the lower atmosphere of the planet, as well as escaping hydrogen and metals in the upper atmosphere. From a re-analysis of near-ultraviolet transmission observations of HD 209458b we detect ionized iron (Fe+) absorption in a 100 Å-wide range around 2370 Å, lying beyond the planetary Roche lobe. However, we do not detect absorption of equally strong Fe+ lines expected to be around 2600 Å. Further, we find no evidence for absorption by neutral magnesium (Mg), ionized magnesium (Mg+), nor neutral iron (Fe). These results avoid the conflict with theoretical models previously found by Vidal-Madjar et al., which detected Mg but did not detect Mg+ from this same data set. Our results indicate that hydrodynamic escape is strong enough to carry atoms as heavy as iron beyond the planetary Roche lobe, even for planets less irradiated than the extreme ultra-hot Jupiters such as WASP-12 b and KELT-9 b. The detection of iron and nondetection of magnesium in the upper atmosphere of HD 209458b can be explained by a model in which the lower atmosphere forms (hence, sequesters) primarily magnesium-bearing condensates, rather than iron condensates. This is suggested by current microphysical models. The inextricable synergy between upper- and lower-atmosphere properties highlights the value of combining observations that probe both regions.

Keywords: exoplanet atmospheres; transmission spectroscopy; radiative transfer
Bayesian Synthesis of Astrometric Wobble and Total Light Curves in Close Binary Supermassive Black Holes

We test the potential of Bayesian synthesis of upcoming multi-instrument data to extract orbital parameters and individual light curves of close binary supermassive black holes (CB-SMBH) with subparsec separations. Next-generation interferometers, will make possible the observation of astrometric wobbles in CB-SMBH. Combining them with periodic variable time-domain data from surveys like the Vera C. Rubin Legacy Survey of Space and Time, allows for more information on CB-SMBH candidates compared to standalone observational methods. Our method reliably determines binary parameters and component fluxes from binary total flux across long-term, intermediate, and short-term binary dynamics and observational configurations, assuming 10 annual observations, even in short period "q-accrete" objects. Expected CB-SMBH astrometric wobbles constructed from binary dynamical parameters might serve in refining observational strategies for CB-SMBH. Combination of inferred mass ratio, light curves of binary components, and observed photocenter wobbles can be a proxy for the activity states of CB-SMBH components.

Keywords: active galactic nuclei; supermassive black holes; astronomical instrumentation; sky surveys; astrostatistics techniques
Modeling the Chemical Enrichment History of the Bulge Fossil Fragment Terzan 5

Terzan 5 is a heavily obscured stellar system located in the inner Galaxy. It has been postulated to be a stellar relic, a bulge fossil fragment witnessing the complex history of the assembly of the Milky Way bulge. In this paper, we follow the chemical enrichment of a set of putative progenitors of Terzan 5 to assess whether the chemical properties of this cluster fit within a formation scenario in which it is the remnant of a primordial building block of the bulge. We can explain the metallicity distribution function and the runs of different element-to-iron abundance ratios as functions of [Fe/H] derived from optical-infrared spectroscopy of giant stars in Terzan 5 by assuming that the cluster experienced two major star formation bursts separated by a long quiescent phase. We further predict that the most metal-rich stars in Terzan 5 are moderately He-enhanced, and we predict a large spread of He abundances in the cluster, Y ≃ 0.26-0.335. We conclude that current observations fit within a formation scenario in which Terzan 5 originated from a pristine or slightly metal-enriched gas clump about one order of magnitude more massive than its present-day mass. Losses of gas and stars played a major role in shaping Terzan 5 the way we see it now. The iron content of the youngest stellar population is better explained if the white dwarfs that give rise to type Ia supernovae (the main Fe factories) sink toward the cluster center, rather than being stripped by the strong tidal forces exerted by the Milky Way in the outer regions.

Keywords: galactic bulge; galactic archaeology; galaxy chemical evolution; star clusters; stellar abundances
A Multiwavelength Look at the GJ 9827 System: No Evidence of Extended Atmospheres in GJ 9827b and d from HST and CARMENES Data

GJ 9827 is a bright star hosting a planetary system with three transiting planets. As a multiplanet system with planets that sprawl within the boundaries of the radius gap between terrestrial and gaseous planets, GJ 9827 is an optimal target to study the evolution of the atmospheres of close-in planets with a common evolutionary history and their dependence from stellar irradiation. Here we report on the Hubble Space Telescope (HST) and CARMENES transit observations of GJ 9827 planets b and d. We performed a stellar and ISM characterization from the ultraviolet HST spectra, obtaining fluxes for Lyα and Mg II of F(Lyα) = (5.42 ${}_{-0.75}^{+0.96}$ ) × 10-13 erg cm-2 s-1 and F(MgII) = (5.64 ± 0.24) × 10-14 erg cm-2 s-1. We also investigated a possible absorption signature in Lyα in the atmosphere of GJ 9827b during a transit event from HST spectra, as well as Hα and He I signature for the atmosphere of GJ 9827b and d from CARMENES spectra. We found no evidence of an extended atmosphere in either of the planets. This result is also supported by our analytical estimations of mass loss based on the measured radiation fields for all three planets of this system, which led to a mass-loss rate of 0.4, 0.3, and 0.1 planetary masses per Gyr for GJ 9827b, c, and d, respectively. These values indicate that the planets could have lost their volatiles quickly in their evolution and probably do not retain an atmosphere at the current stage.

Keywords: exoplanet atmospheres; exoplanet astronomy; stellar chromospheres; ultraviolet sources
Radiative Transfer Modeling of an SN 1987A Light Echo-AT 2019xis

We use a Monte Carlo radiative transfer model (MCRTM) to simulate the UBVRI light curves, images, and linear polarization of a light echo from supernova SN 1987A in the Large Magellanic Cloud (LMC) using various dust cloud shapes, sizes, and optical properties. We compare the theoretical simulations to the observations of AT 2019xis, a light echo detected at a large angular distance (4'05) from SN 1987A. We estimate the size and optical thickness of the dust cloud based on the simulation results and the observations of the Optical Gravitational Lensing Experiment (OGLE-IV) Transient Detection System (OTDS) I-band light curve. The mass of the dust cloud is calculated using the estimated size, optical thickness, and extinction coefficient. If the dust cloud is assumed to correspond to a gas-to-dust ratio of 300, the total mass of the dust cloud is approximately 7.8-9.3 M⊙. Based on these theoretical models, we show that the morphological shapes of the light echoes in the wavelength range of or shorter than the U band to be very different from those in the longer wavelength bands, and the difference carries important information on the early UV radiation of SN 1987A.

Keywords: interstellar dust; interstellar scattering; interstellar clouds; core-collapse supernovae; radiative transfer simulations; type ii supernovae
TOI-4562b: A Highly Eccentric Temperate Jupiter Analog Orbiting a Young Field Star

We report the discovery of TOI-4562b (TIC-349576261), a Jovian planet orbiting a young F7V-type star, younger than the Praesepe/Hyades clusters (<700 Myr). This planet stands out because of its unusually long orbital period for transiting planets with known masses (P orb = 225.11781 ${}_{-0.00022}^{+0.00025}$ days) and because it has a substantial eccentricity (e = 0.76 ${}_{-0.02}^{+0.02}$ ). The location of TOI-4562 near the southern continuous viewing zone of TESS allowed observations throughout 25 sectors, enabling an unambiguous period measurement from TESS alone. Alongside the four available TESS transits, we performed follow-up photometry using the South African Astronomical Observatory node of the Las Cumbres Observatory and spectroscopy with the CHIRON spectrograph on the 1.5 m SMARTS telescope. We measure a radius of ${1.118}_{+0.013}^{-0.014}$ R J and a mass of 2.30 ${}_{-0.47}^{+0.48}$ M J for TOI-4562b. The radius of the planet is consistent with contraction models describing the early evolution of the size of giant planets. We detect tentative transit timing variations at the ~20 minutes level from five transit events, favoring the presence of a companion that could explain the dynamical history of this system if confirmed by future follow-up observations. With its current orbital configuration, tidal timescales are too long for TOI-4562b to become a hot Jupiter via high-eccentricity migration though it is not excluded that interactions with the possible companion could modify TOI-4562b's eccentricity and trigger circularization. The characterization of more such young systems is essential to set constraints on models describing giant-planet evolution.

Keywords: exoplanets; exoplanet migration; young stellar objects; extrasolar gaseous giant planets; elliptical orbits; stellar activity; transit timing variation method
Synchrotron Intensity and Polarization Gradients: Tools to Obtain the Magnetization Level in a Turbulent Medium

Synchrotron intensity and polarization gradients (SIG and SPG), proposed by Lazarian et al. and Lazarian & Yuen, present a new way to recover the mean magnetic field direction in the plane of the sky. To measure the magnetization level, Lazarian et al. suggested that the methods used in the context of the "Velocity Gradient Technique" could also be used on the SIG and SPG contexts. In this work we test the two proposed methods, named "top-base" and the circular standard deviation, "S," to obtain the level of magnetization from synchrotron emission. In order to test the methods, we generate synthetic observations from magnetohydrodynamic computer simulations, with Alfvénic Mach numbers, MA ∈ [0.2,1.7]. Using a Bayesian analysis we find that the circular standard deviations for the SIG and SPG methods are able to recover the magnetization for cases with signal-to-noise ratio ≳5. We found that for weak Faraday depolarization and different angles between the magnetic field direction and the line of sight the magnetization level can still be estimated.

Keywords: magnetohydrodynamics; interstellar synchrotron emission; interstellar medium; interstellar plasma
Early Results from GLASS-JWST. III. Galaxy Candidates at z 9-15

We present the results of a first search for galaxy candidates at z ~ 9-15 on deep seven-band NIRCam imaging acquired as part of the GLASS-James Webb Space Telescope (JWST) Early Release Science Program on a flanking field of the Frontier Fields cluster A2744. Candidates are selected via two different renditions of the Lyman-break technique, isolating objects at z ~ 9-11, and z ~ 9-15, respectively, supplemented by photometric redshifts obtained with two independent codes. We find five color-selected candidates at z > 9, plus one additional candidate with photometric redshift z phot ≥ 9. In particular, we identify two bright candidates at M UV ≃ -21 that are unambiguously placed at z ≃ 10.6 and z ≃ 12.2, respectively. The total number of galaxies discovered at z > 9 is in line with the predictions of a nonevolving luminosity function. The two bright ones at z > 10 are unexpected given the survey volume, although cosmic variance and small number statistics limits general conclusions. This first search demonstrates the unique power of JWST to discover galaxies at the high-redshift frontier. The candidates are ideal targets for spectroscopic follow-up in Cycle-2. *Based on observations collected with JWST under the ERS program ID 1324 (PI T. Treu).

Keywords: reionization
The Nature of Jets in Double-peaked Emission-line AGN in the KISSR Sample

Double-peaked emission-line AGN (DPAGN) have been regarded as binary black hole candidates. We present here results from parsec-scale radio observations with the Very Long Baseline Array (VLBA) of five DPAGN belonging to the KISSR sample of emission-line galaxies. This work concludes our pilot study of nine type 2 Seyfert and LINER DPAGN from the KISSR sample. In the nine sources, dual compact cores are only detected in the "offset AGN," KISSR 102. However, the overall incidence of jets in the eight sources that were detected with the VLBA is ≥60%. We find a difference in the "missing flux density" going from the Very Large Array to VLBA scales between Seyferts and LINERs, with LINERs showing less missing flux density on parsec-scales. Using the emission-line modeling code, MAPPINGS III, we find that the emission lines are likely to be influenced by jets in 5/9 sources. Jet-medium interaction is the likely cause of the emission-line splitting observed in the SDSS spectra of these sources. Jets in radio-quiet AGN are therefore energetically capable of influencing their parsec- and kpc-scale environments, which makes them agents of "radio AGN feedback" (similar to radio-loud AGN).

Keywords: seyfert galaxies
SN2019dge: A Helium-rich Ultra-stripped Envelope Supernova

We present observations of ZTF18abfcmjw (SN2019dge), a helium-rich supernova with a fast-evolving light curve indicating an extremely low ejecta mass (≈0.33 M⊙) and low kinetic energy (≈1.3 × 1050 erg). Early-time (<4 days after explosion) photometry reveals evidence of shock cooling from an extended helium-rich envelope of ∼0.1 M⊙ located ∼1.2 × 1013 cm from the progenitor. Early-time He II line emission and subsequent spectra show signatures of interaction with helium-rich circumstellar material, which extends from ≳5 × 1013 cm to ≳2 × 1016 cm. We interpret SN2019dge as a helium-rich supernova from an ultra-stripped progenitor, which originates from a close binary system consisting of a mass-losing helium star and a low-mass main-sequence star or a compact object (i.e., a white dwarf, a neutron star, or a black hole). We infer that the local volumetric birth rate of 19dge-like ultra-stripped SNe is in the range of 1400-8200 $\,{\mathrm{Gpc}}^{-3}\,{\mathrm{yr}}^{-1}$ (i.e., 2%-12% of core-collapse supernova rate). This can be compared to the observed coalescence rate of compact neutron star binaries that are not formed by dynamical capture.

Keywords: supernovae; core-collapse supernovae; neutron stars; surveys
Distinct Thermal Emission from GRB 190109A

The gamma-ray bursts (GRBs) with distinct thermal components are rarely detected, especially in cases with thermal components throughout the prompt phase. Recently, Fermi/GBM, Swift/BAT, and Swift/XRT detected the special long-duration GRB 190109A, which has four pulses in the prompt gamma-ray emission, i.e, Pulse I (-4 to 20 s), Pulse II (20-50 s), Pulse III (50-90 s), and Pulse IV (90-120 s). GRB 190109A exhibits a very hard low-energy index (α ~ 1) in the Band function relative to the typical GRBs (α ~ - 1). In the whole burst prompt emission, we find distinct thermal emissions in the time-resolved spectra throughout four pulses. The blackbody (BB) temperature kT varies from 24.7 to 8.2 keV for Pulse I to Pulse IV. We also obtain the relation of F ∝ kT -0.40 for the early phase (Pulse I) and F ∝ kT 3.33±0.76 for the late phase (Pulses II-IV), respectively. The significant deviation of the kT - F relation in the early epochs from that in the late epochs likely suggests that the BB spectra origin of the early phase (Pulse I) may have disparate physical processes from those of the late phase (Pulses II-IV). For instance, it may be the transition from cocoon surroundings by a jet to the photosphere of the matter-dominated jet. A jet break is found in the late X-ray afterglow, which is in keeping with the standard external shock afterglow model in the interstellar medium circumburst.

Keywords: gamma-ray bursts
Propagating Uncertainties in the SALT3 Model-training Process to Cosmological Constraints

Type Ia supernovae (SNe Ia) are standardizable candles that must be modeled empirically to yield cosmological constraints. To understand the robustness of this modeling to variations in the model-training procedure, we build an end-to-end pipeline to test the recently developed SALT3 model. We explore the consequences of removing pre-2000s low-z or poorly calibrated U-band data, adjusting the amount and fidelity of SN Ia spectra, and using a model-independent framework to simulate the training data. We find that the SALT3 model surfaces are improved by having additional spectra and U-band data, and can be shifted by ~5% if host-galaxy contamination is not sufficiently removed from SN spectra. We find that resulting measurements of w are consistent to within 2.5% for all of the training variants explored in this work, with the largest shifts coming from variants that add color-dependent calibration offsets or host-galaxy contamination to the training spectra and those that remove pre-2000s low-z data. These results demonstrate that the SALT3 model-training procedure is largely robust to reasonable variations in the training data, but that additional attention must be paid to the treatment of spectroscopic data in the training process. We also find that the training procedure is sensitive to the color distributions of the input data-the resulting w measurement can be biased by ~2% if the color distribution is not sufficiently wide. Future low-z data, particularly u-band observations and high signal-to-noise ratio SN Ia spectra, will help to significantly improve SN Ia modeling in the coming years.

Keywords: type ia supernovae; cosmology
Statistical Distribution Function of Orbital Spacings in Planetary Systems

The minimum orbital separation of planets in long-stable planetary systems is often modeled as a step function, parameterized with a single value ${{\rm{\Delta }}}_{\min }$ (measured in mutual Hill radius of the two neighboring planets). Systems with smaller separations are considered unstable, and planet pairs with greater separations are considered stable. Here we report that a log-normal distribution function for ${{\rm{\Delta }}}_{\min }$ , rather than a single threshold value, provides a more accurate model. From our suite of simulated planetary systems, the parameters of the best-fit log-normal distribution are μ = 1.97 ± 0.02 and σ = 0.40 ± 0.02, such that the mean, median, and mode of ${{\rm{\Delta }}}_{\min }$ are 7.77, 7.17, and 6.11, respectively. This result is consistent with previous estimates for ${{\rm{\Delta }}}_{\min }$ threshold values in the range ~5-8. We find a modest dependence of the distribution of ${{\rm{\Delta }}}_{\min }$ on multiplicity within the system, as well as on planetary mass ratios of the closest planet pair. The overall distribution of nearest-neighbor planetary orbital spacings (measured in the mutual Hill radii and denoted simply as Δ) in long-term stable systems is also well fit with a log-normal distribution, with parameters μ = 3.14 ± 0.03 and σ = 0.76 ± 0.02. In simulations of sets of many planets initially packed very close together, we find that the orbital spacings of long-term stable systems is statistically similar to that in the observed Kepler sample of exoplanetary systems, indicating a strong role of sculpting of planetary architectures by dynamical instabilities.

Keywords: exoplanet systems; exoplanet dynamics