adsabs/SciX_UAT_keywords huggingface dataset:
The Steward Observatory LEO Satellite Photometric Survey

The Steward Observatory LEO Satellite Photometric Survey is a comprehensive observational survey to characterize the apparent brightness of the Starlink and OneWeb low Earth orbit satellites and evaluate the potential impact on astronomy. We report the results of over 16,000 independent measurements of nearly 2800 individual satellites. In addition to photometry, we also measured the astrometric position of each satellite and evaluated the accuracy of predicting satellite position with the available two-line element sets. The apparent brightness of a satellite seen in the sky is not constant and depends on the Sun-satellite-observer geometry. To capture this, we designed the survey to create an all-geometries set of measurements to fully characterize the brightness of each population of satellites as seen in the sky. We visualize the data with sky-plots that show the correlation of apparent brightness with on-sky position and relative Sun-satellite-observer geometry. The sky-plots show where in the sky the satellites are brightest. In addition to visual magnitudes, we also present two new metrics: the expected photon flux and the effective albedo. The expected photon flux metric assesses the potential impact on astronomy sensors by predicting the flux for a satellite trail in an image from a theoretical 1 m class telescope and sensor. The effective albedo metric assesses where a satellite is more reflective than baseline, which ties to the physical structure of the satellite and indicates the potential for brightness-reducing design changes. We intend to use this methodology and resulting data to inform the astronomy community about satellite brightness. Observing programs use a variety of telescopes and instruments and look at different parts of the sky. With the expected photon flux metric and a complete all-sky characterization of satellite brightness, observers can evaluate the potential impacts to their projects and possibly avoid the worst effects.

Keywords: artificial satellites; photometry; astrometry; astronomical site protection; ground-based astronomy; astronomical instrumentation
The Mass-loss History of the Red Hypergiant VY CMa

Imaging and spectroscopy of the knots, clumps, and extended arcs in the complex ejecta of VY CMa confirm a record of high mass-loss events over the past few hundred years. Hubble Space Telescope/Space Telescope Imaging Spectrograph spectroscopy of numerous small knots close to the star allow us to measure their radial velocities from the strong K emission and determine their separate motions, spatial orientations, and time since ejecta. Their ages concentrate around 70, 120, 200, and 250 yr ago. A K emission knot only 50 mas from the star ejected as recently as 1985-1995 may coincide with an H2O maser. Comparison with VY CMa's historic light curve from 1800 to the present shows several knots with ejection times that correspond with extended periods of variability and deep minima. The similarity of this correspondence in VY CMa with the remarkable recent dimming of Betelgeuse and an outflow of gas is apparent. The evidence for similar outflows from the surface of a more typical red supergiant suggests that discrete ejections are more common and surface or convective activity is a major source of mass loss for red supergiants. * Based on observations made with the NASA/ESA Hubble Space Telescope which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Keywords: circumstellar matter; massive stars; red supergiant stars; stellar mass loss
Study of Spectral State Transitions in Black Hole Binaries

The aim of our work is to study the origin of the spectral transitions of transient black hole binaries. In this work, we find signatures of spectral state transition (hard to soft state) while studying the radiative shock for the accretion flow. The gradient of the energy dissipation curve shows a sudden break for certain critical flow parameters when the post-shock dissipation is maximum. This particular feature is common to all spins, and the transitions are well observed. We have identified all the critical flow parameters for different black hole spins. With the dissipation, the inner edge of the disk or the geometry of the post-shock corona reduces progressively and attains a minimum for maximum dissipation. The spin enhances the maximum dissipation further. Using the exact general relativistic framework, we therefore systematically study the various dynamical properties of radiative/dissipative shocks in accretion flows to understand the observed phenomena, namely, the variation of the hard intensity emitted from the evolving Comptonizing medium, the spectral transitions, and their entanglement with the inner edge of the disk, etc. The results presented here might be useful in finding the variation of the hardness ratio and could be a first step to procuring the "q" diagram theoretically.

Keywords: relativistic fluid dynamics; general relativity; accretion; shocks; astrophysical black holes
Gravitomagnetic Interaction of a Kerr Black Hole with a Magnetic Field as the Source of the Jetted GeV Radiation of Gamma-Ray Bursts

We show that the gravitomagnetic interaction of a Kerr black hole (BH) with a surrounding magnetic field induces an electric field that accelerates charged particles to ultra-relativistic energies in the vicinity of the BH. Along the BH rotation axis, these electrons/protons can reach energies of even thousands of petaelectronvolts, so stellar-mass BHs in long gamma-ray bursts (GRBs) and supermassive BHs in active galactic nuclei can contribute to the ultrahigh-energy cosmic rays thorough this mechanism. At off-axis latitudes, the particles accelerate to energies of hundreds of gigaelectronvolts and emit synchrotron radiation at gigaelectronvolt energies. This process occurs within 60° around the BH rotation axis, and due to the equatorial symmetry, it forms a double-cone emission. We outline the theoretical framework describing these acceleration and radiation processes, how they extract the rotational energy of the Kerr BH and the consequences for the astrophysics of GRBs.

Keywords: black hole physics; gamma-ray bursts; active galactic nuclei; ultra-high-energy cosmic radiation
Turbulent Origins of Particle Intensity Dropout in Gradual Solar Energetic Particle Events During Solar Cycle 23

Dropout is a low-energy particle phenomenon in which the particle intensity drops sharply and then rises rapidly during an impulsive or gradual solar energetic particle (SEP) event. We investigated dropouts in gradual SEP events during solar cycle 23, in which we identified 77 dropout periods with an average duration of approximately 1 hr. During most of the dropout periods, we observe large angles between the mean magnetic field and the solar wind velocity, implying that the slab turbulent component dominates. We therefore explore the origin of particle intensity dropout in slab turbulent environments. At a wave frequency of 1 Hz in the spacecraft frame, we observed a significant positive correlation between the turbulent power spectral density (PSD) and its spectral index, both in the ion dissipation range. As the input PSD decreases, the correlation can amplify the reduction factor for pitch-angle scatterings, quickly suppressing particle scattering through the 90° pitch angle. Hence, particle dropout may occur due to lack of spatial diffusion of particles.

Keywords: interplanetary turbulence; solar energetic particles; solar magnetic fields; solar particle emission; solar wind
Probabilistic Detection of Spectral Line Components

Resolved kinematical information, such as from molecular gas in star-forming regions, is obtained from spectral line observations. However, these observations often contain multiple line-of-sight components, making estimates harder to obtain and interpret. We present a fully automatic method that determines the number of components along the line of sight, or the spectral multiplicity, through Bayesian model selection. The underlying open-source framework, based on nested sampling and conventional spectral line modeling, is tested using the large area ammonia maps of NGC 1333 in the Perseus molecular cloud obtained by the Green Bank Ammonia Survey (GAS). Compared to classic approaches, the presented method constrains velocities and velocity dispersions in a larger area. In addition, we find that the velocity dispersion distribution among multiple components did not change substantially from that of a single-fit component analysis of the GAS data. These results showcase the power and relative ease of the fitting and model selection method, which makes it a unique tool to extract maximum information from complex spectral data.

Keywords: computational methods; star forming regions
Observation of Vertically Ejected Plumes Generated by the Impact of Hollow Projectiles at Various Velocities

Recently, impact experiments in space have been conducted in planetary exploration using hollow or internally structured projectiles. In laboratory experiments using hollow projectiles to investigate the differences in crater and ejecta from the case of solid projectiles, a plume perpendicular to the target surface has been observed, which has not been seen in conventional cratering experiments using solid projectiles. In this study, we conducted crater-formation experiments using hollow resin projectiles to understand the mechanism through which vertical plumes form in the case of hollow projectiles. We examined the generation of a vertical plume as a function of the impact velocity, v imp. We found that (i) no vertical plume occurs at v imp < 200 m s-1, (ii) the cases with or without a vertical plume are mixed at 200 < v imp < 350 m s-1, (iii) no vertical plume occurs at 350 < v imp < 800 m s-1, and (iv) a vertical plume occurs at 2 < v imp < 3 km s-1. We qualitatively discussed the generation mechanism of the vertical plume using the results of recovered projectiles. Depending on v imp, an empty hole in which there is no projectile materials can be opened along the central axis, resulting in the generation of a vertical plume.

Keywords: small solar system bodies; impact phenomena
Architecture of Three-planet Systems Predicted from the Observed Protoplanetary Disk of HL Tau

A number of protoplanetary disks (PPDs) observed with the Atacama Large Millimeter/submillimeter Array potentially provide direct examples of initial conditions for planetary systems. In particular, the HL Tau disk has been intensively studied, and its rings/gaps are conventionally interpreted to be a result of unseen massive planets embedded in the gaps. Based on this interpretation, we carried out N-body simulations to investigate the orbital evolution of planets within the PPD and after disk dispersal. Before disk dispersal, our N-body simulations include both migration and mass growth of the planet coupled with the evolution of the disk. By varying the disk parameters, we produce a variety of widely separated planetary systems consisting of three super-Jupiters at the end of disk dispersal. We found that the outer planet is more massive than the inner one, and the migration of the innermost planet is inefficient due to the accretion of outer planet(s). We also showed how the final configuration and the final planetary mass depend on disk parameters. The migration is found to be convergent, and no planet pair has a period ratio less than 2. After disk dispersal, we switch to purely gravitational N-body simulations and integrate the orbits up to 10 Gyr. Most simulated systems remain stable for at least 10 Gyr. We discuss the implications of our result in terms of the observed widely separated planetary systems HR 8799 and PDS 70.

Keywords: protoplanetary disks; planet formation
JWST/NIRSpec Measurements of Extremely Low Metallicities in High Equivalent Width Lyα Emitters

Deep Very Large Telescope/MUSE optical integral field spectroscopy has recently revealed an abundant population of ultra-faint galaxies (M UV ≈ -15; 0.01 L ⋆) at z = 2.9-6.7 due to their strong Lyα emission with no detectable continuum. The implied Lyα equivalent widths can be in excess of 100-200 Å, challenging existing models of normal star formation and indicating extremely young ages, small stellar masses, and a very low amount of metal enrichment. We use JWST/NIRSpec's microshutter array to follow up 45 of these galaxies (11 hr in G235M/F170LP and 7 hr in G395M/F290LP), as well as 45 lower-equivalent width Lyα emitters. Our spectroscopy covers the range 1.7-5.1 micron in order to target strong optical emission lines: Hα, [O III], Hβ, and [N II]. Individual measurements as well as stacks reveal line ratios consistent with a metal-poor nature (2%-40% Z ⊙, depending on the calibration). The galaxies with the highest equivalent widths of Lyα, in excess of 90 Å, have lower [N II]/Hα (1.9σ) and [O III]/Hβ (2.2σ) ratios than those with lower equivalent widths, implying lower gas-phase metallicities at a combined significance of 2.4σ. This implies a selection based on Lyα equivalent width is an efficient technique for identifying younger, less chemically enriched systems.

Keywords: galaxy abundances; high-redshift galaxies; galaxy evolution; galaxy chemical evolution
Front-row Seat of the Recent R Aqr Periastron Passage: X-Ray Multiepoch Spectral and Spatial Analysis

We report on the X-ray spectral and spatial evolution of the symbiotic star R Aqr. Through a multiepoch observational campaign performed with Chandra between 2017 and 2022, we study the X-ray emission of this binary system, composed of an evolved red giant star and a white dwarf (WD). This analysis is particularly timely as the WD approached the periastron in late 2018/early 2019; thus, mass transfer, jet emission, and outburst phenomena are to be expected. Through detailed spectral analysis, we detect a significant rise in the soft X-ray (0.5-2 keV) emission of R Aqr, likely linked to jet emission, followed by a decay toward the previous quiescent state. The hard X-ray emission (5-8 keV) is not immediately affected by the periastron passage; the hard component, after maintaining the same flux level between 2017 and 2021, rapidly decays after 2022. Possible explanations for this are a change in the reflection properties of the medium surrounding the binary, obscuration of the central region by material ejected during the periastron passage, or even the partial/complete destruction of the inner regions of the accretion disk surrounding the WD. In addition to this activity in the central region, extended emission is also detected, likely linked to a hot spot in a pre-outburst-emitted jet, which can be observed moving away from the system's central region.

Keywords: symbiotic binary stars; x-ray binary stars; stellar accretion disks
The DECam Ecliptic Exploration Project (DEEP). V. The Absolute Magnitude Distribution of the Cold Classical Kuiper Belt

The DECam Ecliptic Exploration Project (DEEP) is a deep survey of the trans-Neptunian solar system being carried out on the 4 m Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile using the Dark Energy Camera (DECam). By using a shift-and-stack technique to achieve a mean limiting magnitude of r ∼ 26.2, DEEP achieves an unprecedented combination of survey area and depth, enabling quantitative leaps forward in our understanding of the Kuiper Belt populations. This work reports results from an analysis of 20, 3 deg2 DECam fields along the invariable plane. We characterize the efficiency and false-positive rates for our moving-object detection pipeline, and use this information to construct a Bayesian signal probability for each detected source. This procedure allows us to treat all of our Kuiper Belt object (KBO) detections statistically, simultaneously accounting for efficiency and false positives. We detect approximately 2300 candidate sources with KBO-like motion with signal-to-noise ratios > 6.5. We use a subset of these objects to compute the luminosity function of the Kuiper Belt as a whole, as well as the cold classical (CC) population. We also investigate the absolute magnitude (H) distribution of the CCs, and find consistency with both an exponentially tapered power law, which is predicted by streaming instability models of planetesimal formation, and a rolling power law. Finally, we provide an updated mass estimate for the CC Kuiper Belt of ${M}_{{CC}}({H}_{r}\lt 12)\,=\,{0.0017}_{-0.0004}^{+0.0010}{M}_{\oplus }$ , assuming albedo p = 0.15 and density ρ = 1 g cm‑3.

Keywords: solar system; solar system astronomy; kuiper belt; small solar system bodies; planetary science
Deep Learning-based Fast Spectral Inversion of Hα and Ca II 8542 Line Spectra

A multilayer spectral inversion (MLSI) model has recently been proposed for inferring the physical parameters of plasmas in the solar chromosphere from strong absorption lines taken by the Fast Imaging Solar Spectrograph (FISS). We apply a deep neural network (DNN) technique in order to produce the MLSI outputs with reduced computational costs. We train the model using two absorption lines, Hα and Ca II 8542 Å, taken by FISS, and 13 physical parameters obtained from the application of MLSI to 49 raster scans (~2,000,000 spectra). We use a fully connected network with skip connections and multi-branch architecture to avoid the problem of vanishing gradients and to improve the model's performance. Our test shows that the DNN successfully reproduces the physical parameters for each line with high accuracy and a computing time of about 0.3-0.4 ms per line, which is about 250 times faster than the direct application of MLSI. We also confirm that the DNN reliably reproduces the temporal variations of the physical parameters generated by the MLSI inversion. By taking advantage of the high performance of the DNN, we plan to provide physical parameter maps for all the FISS observations, in order to understand the chromospheric plasma conditions in various solar features.

Keywords: solar chromosphere; neural networks; spectroscopy
The Star Formation Across Cosmic Time (SFACT) Survey. I. Survey Description and Early Results from a New Narrowband Emission-line Galaxy Survey

We introduce the Star Formation Across Cosmic Time (SFACT) survey. SFACT is a new narrowband survey for emission-line galaxies (ELGs) and QSOs being carried out using the wide-field imager on the WIYN 3.5 m telescope. Because of the superior depth and excellent image quality afforded by WIYN, we routinely detect ELGs to r = 25.0. Our survey observations are made using three custom narrowband filters centered on 6590 Å, 6950 Å, and 7460 Å. Due to the sensitivity of the survey, we are able to simultaneously detect sources via a number of different emission lines over a wide range of redshifts. The principal lines detected in SFACT are Hα (redshifts up to 0.144), [O III]λ5007 (redshifts up to 0.500), and [O II]λ3727 (redshifts up to 1.015). In this paper, we detail the properties of the survey as well as present initial results obtained by analyzing our three pilot-study fields. These fields have yielded a total of 533 ELG candidates in an area of 1.50 deg2 (surface density of 355 ELGs deg-2). Follow-up spectra for a subset of the ELG candidates are also presented. One of the key attributes of the SFACT survey is that the ELGs are detected in discrete redshift windows that will allow us to robustly quantify the properties of the star-forming and active galactic nucleus populations as a function of redshift to z = 1 and beyond. The planned acquisition of additional narrowband filters will allow us to expand our survey to substantially higher redshifts.

Keywords: emission line galaxies; starburst galaxies; quasars; surveys; star formation; blue compact dwarf galaxies; dwarf galaxies; galaxy abundances; galaxy evolution; seyfert galaxies; spiral galaxies
Finite Temperature Description of Fermi Gases with In-medium Effective Mass

We investigate Fermi gases at finite temperature for which the in-medium effective mass may not be constant as a function of the density, the temperature, or the chemical potential. We suggest a formalism that separates the terms for which the mass is constant from the terms that explicitly treat the correction due to the in-medium effective mass. We employ the ensemble equivalence in infinite matter to treat these different terms. Our formalism is applied in nuclear matter and we show its goodness by comparing it to an exact treatment based on the numerical calculation of the Fermi integrals.

Keywords: nuclear physics
The Great Markarian 421 Flare of 2010 February: Multiwavelength Variability and Correlation Studies

We report on variability and correlation studies using multiwavelength observations of the blazar Mrk 421 during the month of 2010 February, when an extraordinary flare reaching a level of ∼27 Crab Units above 1 TeV was measured in very high energy (VHE) γ-rays with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) observatory. This is the highest flux state for Mrk 421 ever observed in VHE γ-rays. Data are analyzed from a coordinated campaign across multiple instruments, including VHE γ-ray (VERITAS, Major Atmospheric Gamma-ray Imaging Cherenkov), high-energy γ-ray (Fermi-LAT), X-ray (Swift, Rossi X-ray Timing Experiment, MAXI), optical (including the GASP-WEBT collaboration and polarization data), and radio (Metsähovi, Owens Valley Radio Observatory, University of Michigan Radio Astronomy Observatory). Light curves are produced spanning multiple days before and after the peak of the VHE flare, including over several flare "decline" epochs. The main flare statistics allow 2 minute time bins to be constructed in both the VHE and optical bands enabling a cross-correlation analysis that shows evidence for an optical lag of ∼25-55 minutes, the first time-lagged correlation between these bands reported on such short timescales. Limits on the Doppler factor (δ ≳ 33) and the size of the emission region ( ${\delta }^{-1}{R}_{B}\lesssim 3.8\times {10}^{13}\,{\rm{cm}}$ ) are obtained from the fast variability observed by VERITAS during the main flare. Analysis of 10 minute binned VHE and X-ray data over the decline epochs shows an extraordinary range of behavior in the flux-flux relationship, from linear to quadratic to lack of correlation to anticorrelation. Taken together, these detailed observations of an unprecedented flare seen in Mrk 421 are difficult to explain with the classic single-zone synchrotron self-Compton model.

Keywords: bl lacertae objects; blazars; high energy astrophysics; relativistic jets; markarian galaxies; gamma-ray astronomy; time domain astronomy
Sm and Gd Isotopic Shifts in Eucrites and Implications for Their Cosmic-Ray Exposure History

The isotopic compositions of Sm and Gd in eight eucrites-five from a desert, Dar al Gani (DaG) 380, DaG 391, DaG 411, DaG 443, and DaG 480, and three from nondesert areas, Juvinas, Millibillillie, and Stannern-were determined to understand the cosmic-ray exposure (CRE) history for each meteorite from the isotopic shifts of 149Sm-150Sm and 157Gd-158Gd caused by the neutron capture reactions induced by cosmic-ray irradiation. Seven of the eight samples, excepting DaG 443, show readily detectable isotopic shifts of Sm and Gd corresponding to neutron fluences in the range of (0.28-2.38) × 1015 neutrons cm-2. The degrees of Sm isotopic shifts for six of these seven eucrites can be consistently explained by the CRE age histogram of eucrites obtained in previous studies. Exceptionally, DaG 480 shows larger isotopic shifts of Sm than those expected from the CRE age histogram, suggesting a multiple-irradiation history, including irradiation on the parent body. However, there is no clear difference in the CRE conditions between DaG 480 and other eucrites from the parameter ɛ Sm/ɛ Gd to identify the difference in the thermalization degree of neutrons in association with the CRE conditions.

Keywords: asteroid surfaces; galactic cosmic rays; isotopic abundances