adsabs/SciX_UAT_keywords huggingface dataset:
Early TeV Photons of GRB 221009A Were Absorbed by the Prompt MeV Photons

GRB 221009A produced the highest flux of gigaelectronvolt-teraelectronvolt (GeV-TeV) photons ever observed, allowing the construction of a detailed TeV light curve. We focus on explaining the noticeable dip in the light curve around 2-5 s after the onset of TeV emission. We propose that megaelectronvolt (MeV) photons from the prompt emission annihilate with TeV photons from the afterglow, producing an optical depth that obscures the TeV emission during this period. We develop a two-zone model accounting for the angles of MeV photons that can successfully reproduce the time delay between MeV and TeV photons, the peak optical depth over 3, and the rapid decline in optical depth. Our model supports MeV-TeV annihilation as the cause of the dip and provides reasonable constraints on the emission region parameters.

Keywords: gamma-ray bursts; high energy astrophysics; relativistic jets
Expanding-box Quasilinear Model of the Solar Wind

The expanding-box model of the solar wind has been adopted in the literature within the context of magnetohydrodynamics, hybrid, and full particle-in-cell simulations to investigate the dynamic evolution of the solar wind. The present paper extends such a method to the framework of self-consistent quasilinear kinetic theory. It is shown that the expanding-box quasilinear methodology is largely equivalent to the inhomogeneous steady-state quasilinear model discussed earlier in the literature, but a distinction regarding the description of wave dynamics between the two approaches is also found. The expanding-box quasilinear formalism is further extended to include the effects of a spiraling solar-wind magnetic field as well as collisional age effects. The present finding shows that the expanding-box quasilinear approach and the steady-state global-kinetic models may be employed interchangeably in order to address other more complex problems associated with the solar-wind dynamics.

Keywords: solar wind
Rapid Evolution of Type II Spicules Observed in Goode Solar Telescope On-disk Hα Images

We analyze ground-based chromospheric data acquired at a high temporal cadence of 2 s in wings of the Hα spectral line using the Goode Solar Telescope operating at the Big Bear Solar Observatory. We inspected a 30 minute long Hα-0.08 nm data set to find that rapid blueshifted Hα excursions (RBEs), which are a cool component of type II spicules, experience very rapid morphological changes on timescales of the order of 1 s. Unlike typical reconnection jets, RBEs very frequently appear in situ without any clear evidence of Hα material being injected from below. Their evolution includes inverted "Y," "V," "N," and parallel splitting (doubling) patterns as well as sudden formation of a diffuse region followed by branching. We also find that the same feature may undergo several splitting episodes within about a 1 minute time interval.

Keywords: quiet solar chromosphere; solar coronal heating
Astrophysical Limits on Very Light Axion-like Particles from Chandra Grating Spectroscopy of NGC 1275

Axions/axion-like particles (ALPs) are a well-motivated extension of the Standard Model and are generic within String Theory. The X-ray transparency of the intracluster medium (ICM) in galaxy clusters is a powerful probe of light ALPs (with mass $\lt {10}^{-11}\mathrm{eV}$ ); as X-ray photons from an embedded or background source propagate through the magnetized ICM, they may undergo energy-dependent quantum mechanical conversion into ALPs (and vice versa), imprinting distortions on the X-ray spectrum. We present Chandra data for the active galactic nucleus NGC 1275 at the center of the Perseus cluster. Employing a 490 ks High Energy Transmission Gratings exposure, we obtain a high-quality 1-9 keV spectrum free from photon pileup and ICM contamination. Apart from iron-band features, the spectrum is described by a power-law continuum, with any spectral distortions at the <3% level. We compute photon survival probabilities as a function of ALP mass ma and ALP-photon coupling constant ${g}_{a\gamma }$ for an ensemble of ICM magnetic field models, and then use the NGC 1275 spectrum to constrain the $({m}_{a},{g}_{a\gamma })$ -plane. Marginalizing over magnetic field realizations, the 99.7% credible region limits the ALP-photon coupling to ${g}_{a\gamma }\lt 6-8\times {10}^{-13}\,{\mathrm{GeV}}^{-1}$ (depending upon magnetic field model) for masses ${m}_{a}\lt 1\times {10}^{-12}\mathrm{eV}$ . These are the most stringent limit to date on ${g}_{a\gamma }$ for these light ALPs, and have already reached the sensitivity limits of next-generation helioscopes and light-shining-through-wall experiments. We highlight the potential of these studies with the next-generation X-ray observatories Athena and Lynx, but note the critical importance of advances in relative calibration of these future X-ray spectrometers.

Keywords: particle astrophysics; intracluster medium; x-ray active galactic nuclei; extragalactic magnetic fields; dark matter
Big Three Dragons: Molecular Gas in a Bright Lyman-break Galaxy at z = 7.15

We report Atacama Large Millimeter/submillimeter Array Band 3 observations of CO(6-5), CO(7-6), and [C I](2-1) in B14-65666 ("Big Three Dragons"), one of the brightest Lyman-break galaxies at z > 7 in the rest-frame ultraviolet continuum, far-infrared continuum, and emission lines of [O III] 88 μm and [C II] 158 μm. CO(6-5), CO(7-6), and [C I](2-1), whose 3σ upper limits on the luminosities are approximately 40 times fainter than the [C II] luminosity, are all not detected. The L [C II]/L CO(6-5) and L [C II]/L CO(7-6) ratios are higher than the typical ratios obtained in dusty star-forming galaxies or quasar host galaxies at similar redshifts, and they may suggest a lower gas density in the photodissociated region in B14-65666. By using the (1) [C II] luminosity, (2) dust mass-to-gas mass ratio, and (3) a dynamical mass estimate, we find that the molecular gas mass (M mol) is (0.05-11) × 1010 M ⊙. This value is consistent with the upper limit inferred from the nondetection of mid-J CO and [C I](2-1). Despite the large uncertainty in M mol, we estimate a molecular gas-to-stellar mass ratio (μ gas) of 0.65-140 and a gas depletion time (τ dep) of 2.5-550 Myr; these values are broadly consistent with those of other high-redshift galaxies. B14-65666 could be an ancestor of a passive galaxy at z ≳ 4 if no gas is fueled from outside the galaxy.

Keywords: high-redshift galaxies; galaxies; interstellar medium
Investigating Time Variability of X-Ray Absorption in Swift GRBs

The existence of excess absorption in the X-ray spectra of GRBs is well known, but the primary location of the absorbing material is still uncertain. To gain more knowledge about this, we have performed a time-resolved analysis of the X-ray spectra of 199 GRBs observed by the Swift X-ray telescope, searching for evidence of a decreasing column density ( ${N}_{{\rm{H}},\mathrm{intr}}$ ) that would indicate that the GRBs are ionizing matter in their surroundings. We structured the analysis as Bayesian inference and used an absorbed power law as our baseline model. We also explored alternative spectral models in cases where decreasing absorption was inferred. The analysis reveals seven GRBs that show signs of a decrease in ${N}_{{\rm{H}},\mathrm{intr}}$ , but we note that alternative models for the spectral evolution cannot be ruled out. We conclude that the excess absorption in the vast majority of GRBs must originate on large scales of the host galaxies and/or in the intergalactic medium. Our results also imply that an evolving column density is unlikely to affect the spectral analysis of the early X-ray spectra of GRBs. In line with this, we show that estimating the total ${N}_{{\rm{H}},\mathrm{intr}}$ from early Swift data in Window Timing mode reveals the same increasing trend with redshift as previous results based on data taken at later times, but with tighter constraints.

Keywords: gamma-ray bursts; x-ray astronomy
Searching for Dwarf Galaxies in Gaia DR2 Phase-space Data Using Wavelet Transforms

We present a wavelet-based algorithm to identify dwarf galaxies in the Milky Way in Gaia DR2 data. Our algorithm detects overdensities in 4D position-proper-motion space, making it the first search to explicitly use velocity information to search for dwarf galaxy candidates. We optimize our algorithm and quantify its performance by searching for mock dwarfs injected into Gaia DR2 data and for known Milky Way satellite galaxies. Comparing our results with previous photometric searches, we find that our search is sensitive to undiscovered systems at Galactic latitudes ∣b∣ > 20° and with half-light radii larger than the 50% detection efficiency threshold for Pan-STARRS1 (PS1) at (i) absolute magnitudes of -7 < MV < -3 and distances of 32 kpc < D < 64 kpc, and (ii) MV < -4 and 64 kpc < D < 128 kpc. Based on these results, we predict that our search is expected to discover 5 ± 2 new satellite galaxies: four in the PS1 footprint and one outside the Dark Energy Survey and PS1 footprints. We apply our algorithm to the Gaia DR2 data set and recover ~830 high-significance candidates, out of which we identify a "gold standard" list of ~200 candidates based on cross-matching with potential candidates identified in a preliminary search using Gaia EDR3 data. All of our candidate lists are publicly distributed for future follow-up studies. We show that improvements in astrometric measurements provided by Gaia EDR3 increase the sensitivity of this technique; we plan to continue to refine our candidate list using future data releases.

Keywords: astrometry; proper motions; dwarf galaxies; computational methods
The Spectacular Ultraviolet Flash from the Peculiar Type Ia Supernova 2019yvq

Early observations of Type Ia supernovae (SNe Ia) provide essential clues for understanding the progenitor system that gave rise to the terminal thermonuclear explosion. We present exquisite observations of SN 2019yvq, the second observed SN Ia, after iPTF 14atg, to display an early flash of emission in the ultraviolet (UV) and optical. Our analysis finds that SN 2019yvq was unusual, even when ignoring the initial flash, in that it was moderately underluminous for an SN Ia ( ${M}_{g}\approx -18.5$ mag at peak) yet featured very high absorption velocities ( $v\approx 15{\rm{,0}}00$ km s-1 for Si II λ6355 at peak). We find that many of the observational features of SN 2019yvq, aside from the flash, can be explained if the explosive yield of radioactive 56Ni is relatively low (we measure ${M}_{{56}_{\mathrm{Ni}}}=0.31\pm 0.05\,{M}_{\odot }$ ) and it and other iron-group elements are concentrated in the innermost layers of the ejecta. To explain both the UV/optical flash and peak properties of SN 2019yvq we consider four different models: interaction between the SN ejecta and a nondegenerate companion, extended clumps of 56Ni in the outer ejecta, a double-detonation explosion, and the violent merger of two white dwarfs. Each of these models has shortcomings when compared to the observations; it is clear additional tuning is required to better match SN 2019yvq. In closing, we predict that the nebular spectra of SN 2019yvq will feature either H or He emission, if the ejecta collided with a companion, strong [Ca II] emission, if it was a double detonation, or narrow [O I] emission, if it was due to a violent merger.

Keywords: surveys; supernovae; type ia supernovae; white dwarf stars; observational astronomy
The ALPINE-ALMA [C II] Survey: Size of Individual Star-forming Galaxies at z = 4-6 and Their Extended Halo Structure

We present the physical extent of [C II] 158 μm line-emitting gas from 46 star-forming galaxies at z = 4-6 from the ALMA Large Program to INvestigate C II at Early Times (ALPINE). Using exponential profile fits, we measure the effective radius of the [C II] line (${r}_{{\rm{e}},[{\rm{C}}{\rm\small{II}}]}$) for individual galaxies and compare them with the rest-frame ultraviolet (UV) continuum (${r}_{{\rm{e}},\mathrm{UV}}$) from Hubble Space Telescope images. The effective radius ${r}_{{\rm{e}},[{\rm{C}}{\rm\small{II}}]}$ exceeds ${r}_{{\rm{e}},\mathrm{UV}}$ by factors of ∼2-3, and the ratio of ${r}_{{\rm{e}},[{\rm{C}}{\rm\small{II}}]}/{r}_{{\rm{e}},\mathrm{UV}}$ increases as a function of Mstar. We do not find strong evidence that the [C II] line, rest-frame UV, and far-infrared (FIR) continuum are always displaced over ≃1 kpc scale from each other. We identify 30% of isolated ALPINE sources as having an extended [C II] component over 10 kpc scales detected at 4.1σ-10.9σ beyond the size of rest-frame UV and FIR continuum. One object has tentative rotating features up to ∼10 kpc, where the 3D model fit shows the rotating [C II]-gas disk spread over 4 times larger than the rest-frame UV-emitting region. Galaxies with the extended [C II] line structure have high star formation rate, high stellar mass (Mstar), low Lyα equivalent width, and more blueshifted (redshifted) rest-frame UV metal absorption (Lyα line), as compared to galaxies without such extended [C II] structures. Although we cannot rule out the possibility that a selection bias toward luminous objects may be responsible for such trends, the star-formation-driven outflow also explains all these trends. Deeper observations are essential to test whether the extended [C II] line structures are ubiquitous to high-z star-forming galaxies.

Keywords: galaxy evolution; galaxy formation; circumgalactic medium; interstellar medium
A New Method for Deriving Composition of S-type Asteroids from Noisy and Incomplete Near-infrared Spectra

The surface composition of S-type asteroids can be determined using band parameters extracted from their near-infrared (NIR) spectra (0.7-2.50 μm) along with spectral calibrations derived from laboratory samples. In the past, these empirical equations have been obtained by combining NIR spectra of meteorite samples with information about their composition and mineral abundance. For these equations to give accurate results, the characteristics of the laboratory spectra they are derived from should be similar to those of asteroid spectral data (i.e., similar signal-to-noise ratio (S/N) and wavelength range). Here we present new spectral calibrations that can be used to determine the mineral composition of ordinary chondrite-like S-type asteroids. Contrary to previous work, the S/N of the ordinary chondrite spectra used in this study has been decreased to recreate the S/N typically observed among asteroid spectra, allowing us to obtain more realistic results. In addition, the new equations have been derived for five wavelength ranges encompassed between 0.7 and 2.50 μm, making it possible to determine the composition of asteroids with incomplete data. The new spectral calibrations were tested using band parameters measured from the NIR spectrum of asteroid (25143) Itokawa, and comparing the results with laboratory measurements of the returned samples. We found that the spectrally derived olivine and pyroxene chemistry, which are given by the molar contents of fayalite (Fa) and ferrosilite (Fs), are in excellent agreement with the mean values measured from the samples (Fa28.6±1.1 and Fs23.1±2.2), with a maximum difference of 0.6 mol% for Fa and 1.4 mol% for Fs.

Keywords: asteroids; meteorites
Confirmed Width-Eiso and Width-Liso Relations in Gamma-Ray Bursts: Comparison with the Amati and Yonetoku Relations

The well-known Amati and Yonetoku relations in gamma-ray bursts show strong correlations between the rest-frame νfν spectrum peak energy, Ep,i, and the isotropic energy, Eiso, as well as isotropic peak luminosity, Liso. Recently, Peng et al. showed that the cosmological rest-frame spectral widths are also correlated with Eiso and with Liso. In this paper, we select a sample including 141 BEST time-integrated F spectra and 145 BEST peak flux P spectra observed by Konus-Wind with known redshift to recheck the connection between the spectral width and Eiso as well as Liso. We define six types of absolute spectral widths as the differences between the upper (E2) and lower energy bounds (E1) of the full width at 50%, 75%, 85%, 90%, 95%, and 99% of maximum of the EFE versus E spectra. It is found that all of the rest-frame absolute spectral widths are strongly positively correlated with Eiso as well as Liso for the long burst for both the F and P spectra. All of the short bursts are outliers for the width-Eiso relation, and most of the short bursts are consistent with the long bursts for the width-Liso relation for both F and P spectra. Moreover, all of the location energies, E2 and E1, corresponding to various spectral widths, are also positively correlated with Eiso as well as Liso. We compare all of the relations with the Amati and Yonetoku relations and find that the width-Eiso and width-Liso relations, when the widths are at about 90% maximum of the EFE spectra, almost overlap with the Amati relation and the Yonetoku relation, respectively. The correlations of E2 - Eiso, E1 - Eiso and E2 - Liso, E1 - Liso when the location energies are at 99% of maximum of the EFE spectra are very close to the Amati and Yonetoku relations, respectively. Therefore, we confirm the existence of tight width-Eiso and width-Liso relations for long bursts. We further show that the spectral shape is indeed related to Eiso and Liso. The Amati and Yonetoku relations are not necessarily the best relationships for relating the energy to the Eiso and Liso. They may be special cases of the width-Eiso and width-Liso relations or the energy-Eiso and energy-Liso relations.

Keywords: gamma-ray bursts
Early Low-mass Galaxies and Star-cluster Candidates at z ∼ 6-9 Identified by the Gravitational-lensing Technique and Deep Optical/Near-infrared Imaging

We present very faint dropout galaxies at z ∼ 6-9 with a stellar mass M⋆ down to ${M}_{\star }\sim {10}^{6}\,{M}_{\odot }$ that are found in deep optical/near-infrared (NIR) images of the full data sets of the Hubble Frontier Fields (HFF) program in conjunction with deep ground-based and Spitzer images and gravitational-lensing magnification effects. We investigate stellar populations of the HFF dropout galaxies with the optical/NIR photometry and BEAGLE models made of self-consistent stellar population synthesis and photoionization models, carefully including strong nebular emission impacting on the photometry. We identify 453 galaxies with ${M}_{\star }\sim {10}^{6}\mbox{--}{10}^{9}\,{M}_{\odot }$ . Our best-estimate ${M}_{\star }/{L}_{\mathrm{UV}}$ function is comparable to a model of star formation duration time of 100 Myr that is assumed in Bouwens et al. We derive the galaxy stellar mass functions (GSMFs) at z ∼ 6-9 that agree with those obtained by previous studies at ${M}_{\star }\gtrsim {10}^{8}\,{M}_{\odot }$ , and that extend to ${M}_{\star }\sim {10}^{6}\,{M}_{\odot }$ . Estimating the stellar mass densities ${\rho }_{\star }$ with the GSMFs, we find a very slow evolution from z ∼ 9 to z ∼ 6-7, which is consistent with the one estimated from star formation rate density measurements. In conjunction with the estimates of the galaxy effective radii Re on the source plane, we have pinpointed four objects with low stellar masses ( ${M}_{\star }\leqslant {10}^{7}\,{M}_{\odot }$ ) and very compact morphologies ( ${R}_{{\rm{e}}}\leqslant 40$ pc) that are comparable with those of globular clusters (GCs) in the Milky Way today. These objects are candidates of star clusters, some of which may be related to GCs today.

Keywords: globular star clusters; stellar mass functions; high-redshift galaxies; galaxy formation; strong gravitational lensing
A Comprehensive Optical Search for Pre-explosion Outbursts from the Quiescent Progenitor of SN 2023ixf

We perform a comprehensive search for optical precursor emission at the position of SN 2023ixf using data from the DLT40, ZTF, and ATLAS surveys. By comparing the current data set with precursor outburst hydrodynamical model light curves, we find that the probability of a significant outburst within 5 yr of explosion is low, and the circumstellar material (CSM) ejected during any possible precursor outburst is likely smaller than ~0.015M ⊙. By comparing to a set of toy models, we find that, if there was a precursor outburst, the duration must have been shorter than ~100 days for a typical brightness of M r ≃ -9 mag or shorter than 200 days for M r ≃ -8 mag; brighter, longer outbursts would have been discovered. Precursor activity like that observed in the normal Type II SN 2020tlf (M r ≃ -11.5) can be excluded in SN 2023ixf. If the dense CSM inferred by early flash spectroscopy and other studies is related to one or more precursor outbursts, then our observations indicate that any such outburst would have to be faint and only last for days to months, or it occurred more than 5 yr prior to the explosion. Alternatively, any dense, confined CSM may not be due to eruptive mass loss from a single red supergiant progenitor. Taken together, the results of SN 2023ixf and SN 2020tlf indicate that there may be more than one physical mechanism behind the dense CSM inferred around some normal Type II supernovae.

Keywords: core-collapse supernovae; type ii supernovae; circumstellar matter; stellar mass loss; red supergiant stars
Impact of Ejecta Temperature and Mass on the Strength of Heavy Element Signatures in Kilonovae

A kilonova, the electromagnetic emission produced by compact binary mergers, is formed through a delicate interplay of physical processes, involving r-process nucleosynthesis and interactions between heavy elements and photons through radiative transfer. This complexity makes it difficult to achieve a comprehensive understanding of kilonova spectra. In this study, we aim to enhance our understanding and establish connections between physical parameters and observables through radiative-transfer simulations. Specifically, we investigate how ejecta temperature and element mass influence the resulting kilonova spectrum. For each species, the strength of its line features depends on these parameters, leading to the formation of a distinct region in the parameter space, dubbed the resonance island, where the line signature of that species is notably evident in the kilonova spectrum. We explore its origin and applications. Among explored r-process elements (31 ≤ Z ≤ 92), we find that four species—SrII, YII, BaII, and CeII—exhibit large and strong resonance islands, suggesting their significant contributions to kilonova spectra at specific wavelengths. In addition, we discuss potential challenges and future perspectives in observable heavy elements and their masses in the context of the resonance island.

Keywords: atomic data; radiative transfer; high energy astrophysics