adsabs/SciX_UAT_keywords huggingface dataset:
On the Spectral Peak Energy of Swift Gamma-Ray Bursts

Owing to the narrow energy band of the Swift Burst Alert Telescope (BAT), several urgent issues remain unsolved. We systematically study the properties of a refined sample of 283 Swift/BAT gamma-ray bursts (GRBs) with well-measured spectral peak energy (Ep) at a high confidence level greater than 3σ. We find that the duration (T90) distribution of Swift bursts still exhibits an evident bimodality with a more reliable boundary of T90 ≃ 1.06 s instead of 2 s as found for previously contaminated samples, including bursts without well-peaked spectra, which is very close to the ∼1.27 and ∼0.8 s values suggested in the literature for the Fermi/Gamma-ray Burst Monitor and Swift/BAT catalogs, respectively. The Swift/BAT short and long bursts have comparable mean Ep values of ${87}_{-49}^{+112}$ and ${85}_{-46}^{+101}$ keV, similar to what was found for both types of BATSE bursts, which indicates that the traditional short-hard/long-soft scheme may not be tenable for certain detector energy windows. We also statistically investigate the consistency of distinct methods for Ep estimates and find that a Bayesian approach and BAND function (Band et al.) can always provide consistent evaluations. In contrast, the frequently used cutoff power-law model matches two other methods for lower Ep and overestimates the Ep by more than 70%, as Ep > 100 keV. Peak energies of X-ray flashes, X-ray-rich bursts, and classical GRBs could be an evolutionary consequence of moving from thermal-dominated to nonthermal-dominated radiation mechanisms. Finally, we find that the Ep and the observed fluence (Sγ) in the observer frame are correlated as ${E}_{p}\simeq {[{S}_{\gamma }/({10}^{-5}\mathrm{erg}{\mathrm{cm}}^{-2})]}^{0.28}\times {117.5}_{-32.4}^{+44.7}$ keV, which might be a useful indicator of GRB peak energies.

Keywords: gamma-ray bursts; high energy astrophysics; astronomy data analysis; astrostatistics distributions; interstellar synchrotron emission; interstellar thermal emission; extragalactic astronomy
Testing the Circularity of PSR B0818-41's Carousel

The phenomenon of subpulse drifting is an important single-pulse phenomenon that can potentially provide important insights into the elusive radio emission mechanism in pulsars. We analyze the frequency behavior of the single pulses of B0818-41, observed from 300 to 500 MHz (Band 3 of the upgraded Giant Metrewave Radio Telescope, uGMRT), and compare it to the evolution of the average profile to place constraints on the geometry of the pulsar emission beam. We show that a circular carousel of discrete beamlets, where each beamlet is radially symmetric, is not consistent with the observed behavior, and we describe an alternative consistent range of possible elliptical carousel geometries. We also combine the uGMRT data with some archival Murchison Widefield Array observations and several other published profiles to characterize the profile evolution across a frequency range spanning ~170 MHz to ~1.4 GHz.

Keywords: radio pulsars
Revisiting the Properties of X-Ray Active Galactic Nuclei in the SSA22 Protocluster: Normal Supermassive Black Hole and Host-galaxy Growth for AGNs in a z = 3.09 Overdensity

We analyze the physical properties of eight X-ray-selected active galactic nuclei (AGNs) and one candidate protoquasar system (ADF22A1) in the z = 3.09 SSA22 protocluster by fitting their X-ray-to-IR spectral energy distributions (SEDs) using our SED-fitting code, LIGHTNING (https://www.github.com/rafaeleufrasio/lightning). We recover star formation histories (SFHs) for seven of these systems which are well fit by composite stellar population plus AGN models. We find indications that four out of nine of the SSA22 AGN systems we study have host galaxies below the main sequence, with SFR/SFRMS ≤ -0.4. The remaining SSA22 systems, including ADF22A1, are consistent with obscured supermassive black hole (SMBH) growth in star-forming galaxies. We estimate the SMBH accretion rates and masses, and compare the properties and SFHs of the nine protocluster AGN systems with X-ray-detected AGN candidates in the Chandra Deep Fields (CDF), finding that the distributions of SMBH growth rates, star formation rates (SFRs), SMBH masses, and stellar masses for the protocluster AGNs are consistent with field AGNs. We constrain the ratio between the sample-averaged SSA22 SMBH mass and CDF SMBH mass to <1.41. While the AGNs are located near the density peaks of the protocluster, we find no statistically significant trends between the AGN or host-galaxy properties and their location in the protocluster. We interpret the similarity of the protocluster and field AGN populations together with existing results as suggesting that the protocluster and field AGNs coevolve with their hosts in the same ways, while AGN-triggering events are more likely in the protocluster.

Keywords: active galactic nuclei; agn host galaxies; protoclusters; supermassive black holes; galaxy evolution
The Likely Thickness of Europa's Icy Shell

The icy outer shell of Jupiter's moon Europa is believed to be geologically active, and geological processes within the ice may be key to sustaining chemical disequilibria and potentially habitable environments within the icy shell and ocean. Currently, there are insufficient observational data to determine the thickness of the icy shell, obfuscating crucial aspects of interior processes. Although a range of icy shell thicknesses (~10-1-102 km) have been proposed, not all are equally likely given the current knowledge of Europa. In this study, I construct a probability density distribution for Europa's present-day mean icy shell thickness using a heat flux balance, assuming a simple two-layered model consisting of a partially porous conductive upper layer, and a ductile interior layer that may be experiencing solid-state convection. Current best estimate (CBE) values and uncertainties for ~20 key parameters are propagated through this steady-state heat flux balance to construct ~107 independent simulations. Additionally, I estimate present-day values for the icy shell layer thicknesses, the rocky interior and icy heat fluxes, icy shell thermal properties, and convective ice viscosity. I predict Europa's total icy thickness to be ~23-47 km, with a CBE thickness of ${24.3}_{-1.5}^{+22.8}\,\mathrm{km}$ . This result is highly skewed; icy shells many tens of kilometers thick are much more probable than icy shells <10 km thick. The resulting distributions have key implications for future spaceborne, landed, and subsurface exploration of Europa, as well as studies of icy shell processes, thermal and mechanical state, and habitability across the icy ocean worlds.

Keywords: europa; astrobiology; tectonics
Neutrino Counterparts of Fast Radio Bursts

The discovery of a luminous radio burst, FRB 200428, with properties similar to those of fast radio bursts (FRBs), in coincidence with an X-ray flare from the Galactic magnetar SGR 1935+2154, supports magnetar models for cosmological FRBs. The burst's X-ray to radio fluence ratio, as well as the X-ray spectral shape and peak energy, are consistent with FRB 200428 being the result of an ultra-relativistic shock (powered, e.g., by an ejected plasmoid) propagating into a magnetized baryon-rich external medium; the shock simultaneously generates X-ray/gamma-rays via thermal synchrotron emission from electrons heated behind the shock, and coherent radio emission via the synchrotron maser mechanism. Here, we point out that a unique consequence of this baryon-loaded shock scenario is the generation of a coincident burst of high-energy neutrinos, generated by photohadronic interaction of relativistic ions—heated or accelerated at the shock—with thermal synchrotron photons. We estimate the properties of these neutrino burst FRB counterparts and find that a fraction ∼10-8-10-5 of the flare energy (or ∼10-4-10-1 of the radio isotropic energy) is channeled into production of neutrinos with typical energies ∼TeV-PeV. We conclude by discussing prospects for detecting this signal with IceCube and future high-energy neutrino detectors.

Keywords: radio transient sources; cosmological neutrinos; shocks; gamma-rays; magnetars
CMB Shadows: The Effect of Interstellar Extinction on Cosmic Microwave Background Polarization and Temperature Anisotropy

We evaluate the degradation of the accuracy of the component separation between the cosmic microwave background (CMB) and foreground components caused by neglect of absorption of the CMB's monopole component by the galactic interstellar matter. The amplitude of the temperature anisotropy caused by the CMB shadow, due to dust components, is about 1 μK. This value is comparable to the required noise level necessary to probe non-Gaussianity studies with upcoming CMB experiments. In addition, the amplitude of the polarization caused by the CMB shadow due to dust is comparable to or larger than the rms value of the CMB B-mode polarization, imprinted by primordial gravitational waves. We show that applying a single-power-law model as the dust spectrum to observed multifrequency data introduces systematic errors, which are comparable to or larger than the required noise level for forthcoming CMB B-mode polarization experiments. Deducing the intrinsic spectrum of dust emission from the submillimeter wave band data reduces the systematic error to below the required noise level. However, this method requires dust temperature measurements with an accuracy of better than a few percent. We conclude that the CMB shadow due to dust must be considered in future CMB missions for achieving their targeted sensitivity. Our results will be important to detect the primordial CMB B-mode polarization, with the amplitude of the tensor-to-scalar ratio of r = 10-3.

Keywords: interstellar dust extinction; cosmic microwave background radiation; submillimeter astronomy; interstellar medium
Precision Weak Gravitational Lensing Using Velocity Fields: Fisher Matrix Analysis

Weak gravitational lensing measurements based on photometry are limited by shape noise: the variance in the unknown unlensed orientations of the source galaxies. If the source is a disk galaxy with a well-ordered velocity field, however, velocity field data can support simultaneous inference of the shear, inclination, and position angle, virtually eliminating shape noise. We use the Fisher information matrix formalism to forecast the precision of this method in the idealized case of a perfectly ordered velocity field defined on an infinitesimally thin disk. For nearly face-on targets, one shear component, γ×, can be constrained to $0.003\tfrac{90}{{I}_{0}}\tfrac{25}{{n}_{\mathrm{pix}}}$ , where I0 is the signal-to-noise ratio of the central intensity pixel and npix is the number of pixels across a diameter enclosing 80% of the light. This precision degrades with inclination angle by a factor of 3 by i = 50°. The uncertainty on the other shear component, γ+, is about 1.5 (7) times larger than the γ× uncertainty for targets at i = 10° (50°). For an arbitrary galaxy position angle on the sky, these forecasts apply not to γ+ and γ× as defined on the sky but to two eigenvectors in (γ+, γ×, μ) space, where μ is the magnification. We also forecast the potential of less expensive partial observations of the velocity field, such as slit spectroscopy. We conclude by outlining some ways in which real galaxies depart from our idealized model and thus create random or systematic uncertainties not captured here. In particular, our forecast γ× precision is currently limited only by the data quality rather than scatter in galaxy properties because the relevant type of scatter has yet to be measured.

Keywords: gravitational lensing shear; weak gravitational lensing; gravitational lensing; fisher's information; galaxy kinematics
An Isolated Stellar-mass Black Hole Detected through Astrometric Microlensing

We report the first unambiguous detection and mass measurement of an isolated stellar-mass black hole (BH). We used the Hubble Space Telescope (HST) to carry out precise astrometry of the source star of the long-duration (t E ≃ 270 days), high-magnification microlensing event MOA-2011-BLG-191/OGLE-2011-BLG-0462 (hereafter designated as MOA-11-191/OGLE-11-462), in the direction of the Galactic bulge. HST imaging, conducted at eight epochs over an interval of 6 yr, reveals a clear relativistic astrometric deflection of the background star's apparent position. Ground-based photometry of MOA-11-191/OGLE-11-462 shows a parallactic signature of the effect of Earth's motion on the microlensing light curve. Combining the HST astrometry with the ground-based light curve and the derived parallax, we obtain a lens mass of 7.1 ± 1.3 M ⊙ and a distance of 1.58 ± 0.18 kpc. We show that the lens emits no detectable light, which, along with having a mass higher than is possible for a white dwarf or neutron star, confirms its BH nature. Our analysis also provides an absolute proper motion for the BH. The proper motion is offset from the mean motion of Galactic disk stars at similar distances by an amount corresponding to a transverse space velocity of ~45 km s-1, suggesting that the BH received a "natal kick" from its supernova explosion. Previous mass determinations for stellar-mass BHs have come from radial velocity measurements of Galactic X-ray binaries and from gravitational radiation emitted by merging BHs in binary systems in external galaxies. Our mass measurement is the first for an isolated stellar-mass BH using any technique. *This research is based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Keywords: black holes; gravitational microlensing
Quaia, the Gaia-unWISE Quasar Catalog: An All-sky Spectroscopic Quasar Sample

We present a new, all-sky quasar catalog, Quaia, that samples the largest comoving volume of any existing spectroscopic quasar sample. The catalog draws on the 6,649,162 quasar candidates identified by the Gaia mission that have redshift estimates from the space observatory's low-resolution blue photometer/red photometer spectra. This initial sample is highly homogeneous and complete, but has low purity, and 18% of even the bright (G < 20.0) confirmed quasars have discrepant redshift estimates (∣Δz/(1 + z)∣ > 0.2) compared to those from the Sloan Digital Sky Survey (SDSS). In this work, we combine the Gaia candidates with unWISE infrared data (based on the Wide-field Infrared Survey Explorer survey) to construct a catalog useful for cosmological and astrophysical quasar studies. We apply cuts based on proper motions and colors, reducing the number of contaminants by approximately four times. We improve the redshifts by training a k-Nearest Neighbor model on SDSS redshifts, and achieve estimates on the G < 20.0 sample with only 6% (10%) catastrophic errors with ∣Δz/(1 + z)∣ > 0.2 (0.1), a reduction of approximately three times (approximately two times) compared to the Gaia redshifts. The final catalog has 1,295,502 quasars with G < 20.5, and 755,850 candidates in an even cleaner G < 20.0 sample, with accompanying rigorous selection function models. We compare Quaia to existing quasar catalogs, showing that its large effective volume makes it a highly competitive sample for cosmological large-scale structure analyses. The catalog is publicly available at 10.5281/zenodo.10403370.

Keywords: quasars; catalogs; large-scale structure of the universe; gaia; active galactic nuclei
Misaligned Circumbinary Disks as Efficient Progenitors of Interstellar Asteroids

Gaseous circumbinary disks (CBDs) that are highly inclined to the binary orbit are commonly observed in nature. These disks harbor particles that can reach large mutual inclinations as a result of nodal precession once the gas disk has dissipated. With n-body simulations that include fragmentation we demonstrate that misaligned disks of particles can be efficient progenitors of interstellar asteroids (ISAs). Collisions that take place between particles with large mutual inclinations have large impact velocities, which can result in mass ejection, with a wide range of fragment sizes and ejection velocities. We explore the binary parameters for which the majority of the terrestrial planet-forming material is ejected rather than accreted into planets. The misalignment required to eject significant material decreases with binary eccentricity. If the distribution of binary eccentricity is uniform and the initial particle CBD orientation relative to the binary orbit is isotropic, about 59% of binaries are more likely to eject the majority of their CBD terrestrial planet disk mass through high-velocity body-body collisions than to retain this material and build terrestrial planets. However, binary-disk interactions during the gas disk phase with nonzero disk viscosity will reduce this fraction. The composition, small size, highly elongated shape, and tumbling motion of 'Oumuamua are consistent with ISAs generated by misaligned CBDs.

Keywords: binary stars; asteroids; extrasolar rocky planets; interstellar objects; exoplanet formation
Prospective Annual Detection Rate of High-energy Gamma-Ray Bursts with LHAASO-WCDA

Gamma-ray bursts (GRBs) are considered one of the most violent, explosive events in the universe and serve as high-redshift probes for cosmological study due to their high-energy observations. Such observations, particularly in the GeV regime, have already proven fruitful for deriving useful scientific results, such as the determination of extragalactic background light (EBL) and the stringent constraint on the Lorentz invariance violation effect. Owing to the advantages of a very large effective area, a low threshold energy, a wide field of view, and high duty cycle, the upcoming Large High Altitude Air Shower Observatory-Water Cerenkov Detector Array (LHAASO-WCDA) will have potential sensitivity for discovering GRBs in the 100 GeV energy region. In this work, a sample of GRBs has been generated and examined based on existing observations reported by the Large Area Telescope on board the Fermi satellite. The Fermi spectra are extrapolated to high energy by taking into account the absorption due to the pair production processes occurring between γ rays and EBL. With an assumption that an ultrahigh-energy component accounts for 10% of the total luminosity, it is found that LHAASO-WCDA has a GRB detection rate of ∼one GRB per year.

Keywords: gamma-ray bursts
Superhydrogenated Polycyclic Aromatic Hydrocarbon Molecules: Vibrational Spectra in the Infrared

Superhydrogenated polycyclic aromatic hydrocarbons (PAHs) may be present in H-rich and ultraviolet-poor benign regions. The addition of excess H atoms to PAHs converts the aromatic bonds into aliphatic bonds, the strongest of which falls near 3.4 μm. Therefore, superhydrogenated PAHs are often hypothesized to be a carrier of the 3.4 μm emission feature that typically accompanies the stronger 3.3 μm aromatic C-H stretching feature. To assess this hypothesis, we use density function theory to compute the infrared (IR) vibrational spectra of superhydrogenated PAHs and their ions of various sizes (ranging from benzene and naphthalene to perylene and coronene) and of various degrees of hydrogenation. For each molecule, we derive the intrinsic oscillator strengths of the 3.3 μm aromatic C-H stretch (A_{3.3}) and the 3.4 μm aliphatic C-H stretch (A_{3.4}). By comparing the computationally derived mean ratio of < {A}_{3.4}/{A}_{3.3} > ≈ 1.98 with the mean ratio of the observed intensities < I_{3.4}/I_{3.3} > ≈0.12, we find that the degree of superhydrogenation - the fraction of carbon atoms attached with extra hydrogen atoms - is only ∼2.2% for neutral PAHs, which predominantly emit the 3.3 and 3.4 μm features. We also determine for each molecule the intrinsic band strengths of the 6.2 μm aromatic C-C stretch (A_{6.2}) and the 6.85 μm aliphatic C-H deformation (A_{6.85}). We derive the degree of superhydrogenation from the mean ratio of the observed intensities < {I}_{6.85}/{I}_{6.2} > ≲ 0.10 and < {A}_{6.85}/{A}_{6.2} > ≈ 1.53 for neutrals and < {A}_{6.85}/{A}_{6.2}> ≈ 0.56 for cations to be ≲3.1% for neutrals and ≲8.6% for cations. We conclude that astrophysical PAHs are primarily aromatic and are only marginally superhydrogenated.

Keywords: polycyclic aromatic hydrocarbons; interstellar line emission; line intensities
Coronal Properties of Black Hole X-Ray Binaries in the Hard State as Seen by NuSTAR and Swift

In this work we measure two important phenomenological parameters of corona (and hot accretion flow) in black hole X-ray binaries: the photon index Γ and the electron temperature ${{kT}}_{{\rm{e}}}$ . Thanks to the capability of the Nuclear Spectroscopic Telescope Array in hard X-rays, we measure these two parameters over six orders of magnitude in the 0.1-100 keV X-ray luminosity ${L}_{{\rm{X}}}$ , from ∼5 × 1038 $\mathrm{erg}\,{{\rm{s}}}^{-1}$ down to as low as ∼5 × 1032 $\mathrm{erg}\,{{\rm{s}}}^{-1}$ . We confirm the existence of a "V"-shaped correlation between Γ and ${L}_{{\rm{X}}}$ . Surprisingly, we observe a "Λ"-shaped correlation between ${{kT}}_{{\rm{e}}}$ and ${L}_{{\rm{X}}}$ . The "cooler when brighter" branch in the high-luminosity regime ( ${L}_{{\rm{X}}}$ ≳ 3 × 1036 $\mathrm{erg}\,{{\rm{s}}}^{-1}$ ) agrees with previous results and can be understood under the existing model of Compton scattering in the corona. On the other hand, the apparent "cooler when fainter" (positive ${{kT}}_{{\rm{e}}}$ - ${L}_{{\rm{X}}}$ correlation) branch in the low-luminosity regime ( ${L}_{{\rm{X}}}$ ≲ 3 × 1036 $\mathrm{erg}\,{{\rm{s}}}^{-1}$ ) is unexpected, thus it puts a new challenge to existing models of hot accretion flow/corona.

Keywords: accretion; black hole physics; x-ray binary stars; black holes; compact objects; high energy astrophysics; compact binary stars
Optimizing Simulation Parameters for Weak Lensing Analyses Involving Non-Gaussian Observables

We performed a series of numerical experiments to quantify the sensitivity of the predictions for weak lensing statistics obtained in ray-tracing dark matter (DM)-only simulations, to two hyper-parameters that influence the accuracy as well as the computational cost of the predictions: the thickness of the lens planes used to build past light cones and the mass resolution of the underlying DM simulation. The statistics considered are the power spectrum (PS) and a series of non-Gaussian observables, including the one-point probability density function, lensing peaks, and Minkowski functionals. Counterintuitively, we find that using thin lens planes (< 60 h-1 Mpc on a 240 h-1 Mpc simulation box) suppresses the PS over a broad range of scales beyond what would be acceptable for a survey comparable to the Large Synoptic Survey Telescope (LSST). A mass resolution of 7.2 × 1011 h-1 M⊙ per DM particle (or 2563 particles in a (240 h-1 Mpc)3 box) is sufficient to extract information using the PS and non-Gaussian statistics from weak lensing data at angular scales down to 1' with LSST-like levels of shape noise.

Keywords: weak gravitational lensing; large-scale structure of the universe; computational methods