adsabs/SciX_UAT_keywords huggingface dataset:
Collisional Evolution of the Inner Zodiacal Cloud

The zodiacal cloud is one of the largest structures in the solar system and strongly governed by meteoroid collisions near the Sun. Collisional erosion occurs throughout the zodiacal cloud, yet it is historically difficult to directly measure and has never been observed for discrete meteoroid streams. After six orbits with Parker Solar Probe (PSP), its dust impact rates are consistent with at least three distinct populations: bound zodiacal dust grains on elliptic orbits (α-meteoroids), unbound β-meteoroids on hyperbolic orbits, and a third population of impactors that may be either direct observations of discrete meteoroid streams or their collisional by-products ("β-streams"). The β-stream from the Geminids meteoroid stream is a favorable candidate for the third impactor population. β-streams of varying intensities are expected to be produced by all meteoroid streams, particularly in the inner solar system, and are a universal phenomenon in all exozodiacal disks. We find the majority of collisional erosion of the zodiacal cloud occurs in the range of 10-20 solar radii and expect this region to also produce the majority of pickup ions due to dust in the inner solar system. A zodiacal erosion rate of at least ~100 kg s-1 and flux of β-meteoroids at 1 au of (0.4-0.8) × 10-4 m-2 s-1 are found to be consistent with the observed impact rates. The β-meteoroids investigated here are not found to be primarily responsible for the inner source of pickup ions, suggesting nanograins susceptible to electromagnetic forces with radii below ~50 nm are the inner source of pickup ions. We expect the peak deposited energy flux to PSP due to dust to increase in subsequent orbits, up to 7 times that experienced during its sixth orbit.

Keywords: circumstellar dust; interplanetary dust; debris disks; meteoroids; meteor streams
AstroSat View of the Neutron Star Low-mass X-Ray Binary GX 340+0

Understanding the spectral evolution along the "Z"-shaped track in the hardness-intensity diagram of Z sources, which are a class of luminous neutron star low-mass X-ray binaries, is crucial to probe accretion processes close to the neutron star. Here, we study the horizontal branch (HB) and the normal branch (NB) of the Z source GX 340+0 using AstroSat data. We find that the HB and the NB appear as two different types of X-ray intensity dips, which can appear in any sequence and with various depths. Our 0.8-25 keV spectra of dips and the hard apex can be modeled by the emissions from an accretion disk, a Comptonizing corona covering the inner disk, and the neutron star surface. We find that as the source moves onto the HB, the corona is replenished and energized by the disk and a reduced amount of disk matter reaches the neutron star surface. We also conclude that quasiperiodic oscillations during HB/NB are strongly associated with the corona and explain the evolution of strength and hard lag of this timing feature using the estimated coronal optical depth evolution.

Keywords: x-ray binary stars; accretion; stellar accretion disks
Validation of a Wave Heated 3D MHD Coronal-wind Model using Polarized Brightness and EUV Observations

The physical properties responsible for the formation and evolution of the corona and heliosphere are still not completely understood. 3D MHD global modeling is a powerful tool to investigate all the possible candidate processes. To fully understand the role of each of them, we need a validation process where the output from the simulations is quantitatively compared to the observational data. In this work, we present the results from our validation process applied to the wave turbulence driven 3D MHD corona-wind model WindPredict-AW. At this stage of the model development, we focus the work to the coronal regime in quiescent condition. We analyze three simulation results, which differ by the boundary values. We use the 3D distributions of density and temperature, output from the simulations at the time of around the first Parker Solar Probe perihelion (during minimum of the solar activity), to synthesize both extreme ultraviolet (EUV) and white-light-polarized (WL pB) images to reproduce the observed solar corona. For these tests, we selected AIA 193 Å, 211 Å, and 171 Å EUV emissions, MLSO K-Cor, and LASCO C2 pB images obtained on 2018 November 6 and 7. We then make quantitative comparisons of the disk and off limb corona. We show that our model is able to produce synthetic images comparable to those of the observed corona.

Keywords: magnetohydrodynamical simulations; solar physics; solar coronal heating; solar coronal streamers; solar corona; solar extreme ultraviolet emission; solar radiation; solar atmosphere
A Detailed View of the Broad-line Region in NGC 3783 from Velocity-resolved Reverberation Mapping

We have modeled the full velocity-resolved reverberation response of the Hβ and He II optical broad emission lines in NGC 3783 to constrain the geometry and kinematics of the low-ionization and high-ionization broad-line region (BLR). The geometry is found to be a thick disk that is nearly face-on, inclined at ~18° to our line of sight, and exhibiting clear ionization stratification, with an extended Hβ-emitting region ( ${r}_{\mathrm{median}}={10.07}_{-1.12}^{+1.10}$ lt-day) and a more compact and centrally located He II-emitting region ( ${r}_{\mathrm{median}}={1.33}_{-0.42}^{=+0.34}$ lt-day). In the Hβ-emitting region, the kinematics are dominated by near-circular Keplerian orbits, but with ~40% of the orbits inflowing. The more compact He II-emitting region, on the other hand, appears to be dominated by outflowing orbits. The black hole mass is constrained to be MBH = ${2.82}_{-0.63}^{+1.55}\times {10}^{7}$ M⊙, which is consistent with the simple reverberation constraint on the mass based on a mean time delay, line width, and scale factor of ⟨f⟩ = 4.82. The difference in kinematics between the Hβ- and He II-emitting regions of the BLR is intriguing given the recent history of large changes in the ionizing luminosity of NGC 3783 and evidence for possible changes in the BLR structure as a result.

Keywords: supermassive black holes; seyfert galaxies; reverberation mapping
Probing Magnetic Field Morphology in Galaxy Clusters with the Gradient Technique

Magnetic fields in the intracluster medium affect the structure and the evolution of galaxy clusters. However, their properties are largely unknown, and measuring magnetic fields in galaxy clusters is challenging, especially on large scales outside of individual radio sources. In this work, we probe the plane-of-the-sky orientation of magnetic fields in clusters using the intensity gradients. The technique is a branch of the gradient technique (GT) that employs emission intensity maps from turbulent gas. We utilize Chandra X-ray images of the Perseus, M87, Coma, and A2597 galaxy clusters, and the VLA radio observations of the synchrotron emission from Perseus. We find that the fields predominantly follow the sloshing arms in Perseus, which is in agreement with numerical simulations. The GT-predicted magnetic field shows signatures of magnetic draping around rising bubbles driven by supermassive black hole feedback in the centers of cool-core clusters, as well as draping around substructures merging with the Coma cluster. We calculate the mean-field orientation with respect to the radial direction in these clusters. In the central regions of cool-core clusters, the mean orientation of the magnetic fields is preferentially azimuthal. There is broad agreement between the magnetic field of Perseus predicted using the X-ray and radio data. Further numerical studies and better future observations with higher resolution and larger effective area will help reduce the uncertainties of this method.

Keywords: intracluster medium; extragalactic magnetic fields; magnetohydrodynamics; galaxy clusters
The Impacts of Neutron Star Structure and Base Heating on Type I X-Ray Bursts and Code Comparison

Type I X-ray bursts are rapidly brightening phenomena triggered by thermonuclear burning on the accreting layers of a neutron star (NS). The light curves represent the physical properties of NSs and the nuclear reactions on the proton-rich nuclei. The numerical treatments of the accreting NS and physics of the NS interior are not established, which shows uncertainty in modeling for observed X-ray light curves. In this study, we investigate theoretical X-ray burst models compared with burst light curves with GS 1826-24 observations. We focus on the impacts of the NS mass and radius and base heating on the NS surface using the MESA code. We find a monotonic correlation between the NS mass and the parameters of the light curve. The higher the mass, the longer the recurrence time and the greater the peak luminosity. While the larger the radius, the longer the recurrence time, the peak luminosity remains nearly constant. In the case of increasing base heating, both the recurrence time and peak luminosity decrease. We also examine the above results with a different numerical code, HERES, based on general relativity and consider the central NS. We find that the burst rate, energy, and strength are almost the same in two X-ray burst codes by adjusting the base heat parameter in MESA (the relative errors ≲5%), while the duration and rise times are significantly different between (the relative error is possibly ~50%). The peak luminosity and the e-folding time change irregularly between two codes for different accretion rates.

Keywords: x-ray bursts; neutron stars; nuclear abundances; accretion
The Destiny of Dark Matter

The majority of baryons, which account for 15% of the matter in the Universe, will end their lives as carbon and oxygen inside cold black dwarfs. Dark matter (DM) makes up the remaining 85% of the matter in the Universe; however, the fate of DM is unknown. Here we show that the destiny of purely gravitationally interacting DM particles follows one of two possible routes. The first possible route, the "radiation-destiny" scenario, is that massive DM particles lose sufficient energy through gravitational radiation, causing them to spiral into a supermassive black hole that ultimately disappears through Hawking radiation. The second possible route, the "drifting-alone" destiny, applies to lighter DM particles, where only the central DM halo region spirals into the central BH, which is then Hawking radiated away. The rest of the DM halo is ripped apart by the accelerated expansion of the Universe.

Keywords: dark matter; cosmology; gravitational waves; black holes
Quantifying Feedback from Narrow Line Region Outflows in Nearby Active Galaxies. IV. The Effects of Different Density Estimates on the Ionized Gas Masses and Outflow Rates

Active galactic nuclei (AGN) can launch outflows of ionized gas that may influence galaxy evolution, and quantifying their full impact requires spatially resolved measurements of the gas masses, velocities, and radial extents. We previously reported these quantities for the ionized narrow-line region outflows in six low-redshift AGN, where the gas velocities and extents were determined from Hubble Space Telescope long-slit spectroscopy. However, calculating the gas masses required multicomponent photoionization models to account for radial variations in the gas densities, which span ~6 orders of magnitude. To simplify this method for larger samples with less spectral coverage, we compare these gas masses with those calculated from techniques in the literature. First, we use a recombination equation with three different estimates for the radial density profiles. These include constant densities, those derived from [S II], and power-law profiles based on constant values of the ionization parameter (U). Second, we use single-component photoionization models with power-law density profiles based on constant U, and allow U to vary with radius based on the [O III]/Hβ ratios. We find that assuming a constant density of n H = 102 cm-3 overestimates the gas masses for all six outflows, particularly at small radii where the outflow rates peak. The use of [S II] marginally matches the total gas masses, but also overestimates at small radii. Overall, single-component photoionization models where U varies with radius are able to best match the gas mass and outflow rate profiles when there are insufficient emission lines to construct detailed models.

Keywords: interstellar medium wind; galaxy winds; galaxy kinematics; supermassive black holes; markarian galaxies; seyfert galaxies; emission line galaxies; agn host galaxies; active galactic nuclei; active galaxies
JWST Imaging of the Cartwheel Galaxy Reveals Dust Associated with SN 2021afdx

We present near- and mid-infrared (0.9-18 μm) photometry of supernova (SN) 2021afdx, which was imaged serendipitously with the James Webb Space Telescope (JWST) as part of its Early Release Observations of the Cartwheel Galaxy. Our ground-based optical observations show it is likely to be a Type IIb SN, the explosion of a yellow supergiant, and its infrared spectral energy distribution (SED) ≈200 days after explosion shows two distinct components, which we attribute to hot ejecta and warm dust. By fitting models of dust emission to the SED, we derive a dust mass of $({3.8}_{-0.3}^{+0.5})\times {10}^{-3}\ {M}_{\odot }$ , which is the highest yet observed in a Type IIb SN but consistent with other Type II SNe observed by the Spitzer Space Telescope. We also find that the radius of the dust is significantly larger than the radius of the ejecta, as derived from spectroscopic velocities during the photospheric phase, which implies that we are seeing an infrared echo off of preexisting dust in the progenitor environment, rather than dust newly formed by the SN. Our results show the power of JWST to address questions of dust formation in SNe, and therefore the presence of dust in the early universe, with much larger samples than have been previously possible.

Keywords: core-collapse supernovae; supernovae; type ii supernovae; dust formation
Trends in Silicates in the β Pictoris Disk

While β Pic is known to host silicates in ring-like structures, whether the properties of these silicate dust vary with stellocentric distance remains an open question. We re-analyze the β Pictoris debris disk spectrum from the Spitzer Infrared Spectrograph (IRS) and a new Infrared Telescope Facility Spectrograph and Imager spectrum to investigate trends in Fe/Mg ratio, shape, and crystallinity in grains as a function of wavelength, a proxy for stellocentric distance. By analyzing a re-calibrated and re-extracted spectrum, we identify a new 18 μm forsterite emission feature and recover a 23 μm forsterite emission feature with a substantially larger line-to-continuum ratio than previously reported. We find that these prominent spectral features are primarily produced by small submicron-sized grains, which are continuously generated and replenished from planetesimal collisions in the disk and can elucidate their parent bodies' composition. We discover three trends about these small grains: as stellocentric distance increases, (1) small silicate grains become more crystalline (less amorphous), (2) they become more irregular in shape, and (3) for crystalline silicate grains, the Fe/Mg ratio decreases. Applying these trends to β Pic's planetary architecture, we find that the dust population exterior to the orbits of β Pic b and c differs substantially in crystallinity and shape. We also find a tentative 3-5 μm dust excess due to spatially unresolved hot dust emission close to the star. From our findings, we infer that the surfaces of large planetesimals are more Fe-rich and collisionally processed closer to the star but more Fe-poor and primordial farther from the star.

Keywords: debris disks; silicate grains; planetary system formation; exoplanet formation; planetesimals; exozodiacal dust; spectroscopy; infrared astronomy
JCMT SCUBA-2 Sub-millimeter Observations of AT2018cow

We present a reprocessing of all the submillimeter observations of the optical transient AT2018cow that were performed simultaneously at 850 μm (350 GHz) and 450 μm (670 GHz) using the Submillimetre Common-User Bolometer Array 2 (SCUBA-2), the 10,000 pixel bolometer continuum camera on the James Clerk Maxwell Telescope on Maunakea, Hawai'i. A bright source was detected in our initial observations. The peak in the longer wavelength spectrum had just passed through the SCUBA-2 region prior to our first observation.

Keywords: transient sources; submillimeter astronomy; high energy astrophysics
Observational Constraints on Cosmic-Ray Escape from Ultrahigh-energy Accelerators

Interactions of ultra-high energy cosmic rays (UHECRs) accelerated in specific astrophysical environments have been shown to shape the energy production rate of nuclei differently from that of the secondary neutrons escaping from the confinement zone. Here, we aim at testing a generic scenario of in-source interactions through phenomenological modeling of the flux and composition of UHECRs. We fit a model in which nucleons and nuclei follow different particle energy distributions to the all-particle energy spectrum and proton spectrum below the ankle energy and distributions of maximum shower depths above this energy, as inferred at the Pierre Auger Observatory. We obtain that the data can be reproduced using a spatial distribution of sources that follows the density of extragalactic matter on both local and large scales, providing hence a realistic set of constraints for the emission mechanisms in cosmic accelerators, for their energetics, and for the abundances of elements at escape from their environments. While the quasi monoelemental increase of the cosmic-ray mass number observed on Earth from ≃2 EeV up to the highest energies calls for nuclei accelerated with a hard spectral index, the inferred flux of protons down to ≃0.6 EeV is shown to require for this population a spectral index significantly softer than that generally obtained up to now. We demonstrate that modeling UHECR data across the ankle substantiates the conjecture of in-source interactions in a robust statistical framework, although pushing the mechanism to the extreme.

Keywords: particle astrophysics; ultra-high-energy cosmic radiation; cosmic ray sources; astronomy data modeling; secondary cosmic rays; spectral index
An FRB Sent Me a DM: Constraining the Electron Column of the Milky Way Halo with Fast Radio Burst Dispersion Measures from CHIME/FRB

The CHIME/FRB project has detected hundreds of fast radio bursts (FRBs), providing an unparalleled population to statistically probe the foreground media that they illuminate. One such foreground medium is the ionized halo of the Milky Way (MW). We estimate the total Galactic electron column density from FRB dispersion measures (DMs) as a function of Galactic latitude using four different estimators, including ones that assume spherical symmetry of the ionized MW halo and ones that imply more latitudinal variation in density. Our observation-based constraints of the total Galactic DM contribution for ∣b∣ ≥ 30°, depending on the Galactic latitude and selected model, span 87.8-141 pc cm-3. This constraint implies upper limits on the MW halo DM contribution that range over 52-111 pc cm-3. We discuss the viability of various gas density profiles for the MW halo that have been used to estimate the halo's contribution to DMs of extragalactic sources. Several models overestimate the DM contribution, especially when assuming higher halo gas masses (~3.5 × 1012 M ⊙). Some halo models predict a higher MW halo DM contribution than can be supported by our observations unless the effect of feedback is increased within them, highlighting the impact of feedback processes in galaxy formation.

Keywords: galactic radio sources; radio bursts; circumgalactic medium; galaxy structure; hot ionized medium; warm ionized medium
Narrow Fe-Kα Reverberation Mapping Unveils the Deactivated Broad-line Region in a Changing-look Active Galactic Nucleus

"Changing-look active galactic nuclei" (CLAGNs) are known to change their apparent types between types 1 and 2, usually accompanied by a drastic change in their luminosity on timescales of years. However, it is still unclear whether materials in broad-line regions (BLRs) in CLAGNs appear and disappear during the type-transition or remain at the same location while the line production is simply activated or deactivated. Here we present our X-ray-optical monitoring results of a CLAGN, NGC 3516, by Suzaku, Swift, and ground telescopes, with our primary focus on the narrow Fe-Kα emission line, which is an effective probe of the BLR materials. We detected significant variations of the narrow Fe-Kα line on a timescale of tens of days during the type-2 (faint) phase in 2013-2014, and conducted "narrow Fe-Kα reverberation mapping," comparing its flux variation with those of the X-ray continuum from a corona and B-band continuum from an accretion disk. We derived, as a result, a time lag of ${10.1}_{-5.6}^{+5.8}$ days (1σ errors) for the Fe-Kα line behind the continuum, which is consistent with the location of the BLR determined in optical spectroscopic reverberation mapping during the type-1 (bright) phase. This finding shows that the BLR materials remained at the same location without emitting optical broad lines during the type-2 phase. Considering the drastic decrease of the radiation during the type-transition, our result is possibly inconsistent with the hotly discussed formation models of the BLR, which propose that the radiative pressure from an accretion disk should be the main driving force.

Keywords: x-ray active galactic nuclei; active galactic nuclei; active galaxies
Stellar Tidal Disruption Events with Abundances and Realistic Structures (STARS): Library of Fallback Rates

We present the STARS library, a grid of tidal disruption event (TDE) simulations interpolated to provide the mass fallback rate (dM/dt) to the black hole for a main-sequence star of any stellar mass, stellar age, and impact parameter. We use a one-dimensional stellar evolution code to construct stars with accurate stellar structures and chemical abundances, then perform tidal disruption simulations in a three-dimensional adaptive-mesh hydrodynamics code with a Helmholtz equation of state, in unprecedented resolution: from 131 to 524 cells across the diameter of the star. The interpolated library of fallback rates is available on GitHub (github.com/jamielaw-smith/STARS_library) and version 1.0.0 is archived on Zenodo; one can query the library for any stellar mass, stellar age, and impact parameter. We provide new fitting formulae for important disruption quantities ( ${\beta }_{\mathrm{crit}},{\rm{\Delta }}M,{\dot{M}}_{\mathrm{peak}},{t}_{\mathrm{peak}},{n}_{\infty }$ ) as a function of stellar mass, stellar age, and impact parameter. Each of these quantities varies significantly with stellar mass and stellar age, but we are able to reduce all of our simulations to a single relationship that depends only on stellar structure, characterized by a single parameter ${\rho }_{c}/\bar{\rho }$, and impact parameter β. We also find that, in general, more centrally concentrated stars have steeper dM/dt rise slopes and shallower decay slopes. For the same ΔM, the dM/dt shape varies significantly with stellar mass, promising the potential determination of stellar properties from the TDE light curve alone. The dM/dt shape depends strongly on stellar structure and to a certain extent stellar mass, meaning that fitting TDEs using this library offers a better opportunity to determine the nature of the disrupted star and the black hole.

Keywords: black hole physics; active galaxies; galaxy nuclei; gravitation; hydrodynamics; main sequence stars; tidal disruption