adsabs/SciX_UAT_keywords huggingface dataset:
Feeding the Accretion Disk from the Dusty Torus in a Reddened Quasar

We present here a detailed analysis of an unusual absorption line system in the quasar SDSS J122826.79+100532.2. The absorption lines in the system have a common redshifted velocity structure starting from v ~ 0 and extending to ~1000 km s-1, and are clearly detected in the hydrogen Balmer series up to Hι, in the metastable neutral helium triplet, and in optical lines of excited states of single ionized iron. We estimated that the absorber has a density nH ≈ 108.4 cm-3 and an ionization parameter U ≈ 10-1.2, thereupon we located it at rabs ≈ 1.5 pc from the central supermassive black hole. The inferred distance is remarkably similar to the evaporation radius for dust grains revap ≈ 1 pc in the quasar. Thus the absorber may be a probe of an inflow starting from the dusty torus and feeding the accretion disk. Both the featureless continuum and the broad emission lines are heavily reddened with E(B - V) ≈ 0.66, in contrast to the narrow emission lines whose reddening is negligible. The dusty medium could be located in between the broad and narrow emission line regions, and possibly be associated with a "cold" narrow absorption line system detected in Ca II and Na I doublets nearly unshifted from the quasar systemic velocity. SDSS J122826.79+100532.2 might represent such a rare case that both the inflow and the torus could be tracked by absorption lines.

Keywords: quasars; quasar absorption line spectroscopy
A New Method to Constrain the Origins of Dark-matter-free Galaxies and Their Unusual Globular Clusters

We present a novel method to constrain the past collisional evolution of observed globular cluster (GC) systems, in particular their mass functions. We apply our method to a pair of galaxies hypothesized to have recently undergone an episode of violent relaxation due to a strong galaxy-galaxy interaction, namely, NGC 1052-DF2 and NGC 1052-DF4. We begin by exploring the observational evidence for a collisional origin for these two recently discovered ultradiffuse galaxies observed in the NGC 1052 group, posited in the literature to be dark matter free. We compute the timescales for infall to the central nucleus due to dynamical friction for the GCs in these galaxies, using the shortest of these times to constrain how long ago a galaxy-galaxy interaction could have occurred. We go on to quantify the initial GC numbers and densities needed for significant collisional evolution to occur within the allotted times and show that, if the hypothesis of a previous galaxy-galaxy interaction is correct, a paucity of low-mass GCs should be revealed by deeper observational surveys. If any are found, they should be more spatially extended than the currently observed GC population. Finally, we apply our method to these galaxies, in order to illustrate its efficacy in constraining their dynamical evolution. Our results motivate more complete observations of the GC luminosity functions in these galaxies, in addition to future studies aimed at combining the method presented here with a suite of numerical simulations in order to further constrain the origins of the curious GC populations in these (and other) galaxies.

Keywords: galaxy clusters; interacting galaxies; globular star clusters; stellar dynamics
Near-infrared Spectroscopy of a Massive Young Stellar Object in the Direction toward the Galactic Center: XCN and Aromatic C-D Features

We report near-infrared (2.5-5 μm) long-slit (~30″) spectroscopy of a young stellar object in the direction toward the Galactic center with the Infrared Camera on board the AKARI satellite. The present target is suggested to be AFGL 2006 based on its very red color and close location. The spectra show strong absorption features of H2O and CO2 ices, and emission of H I Brα recombination line and the 3.3 μm band, the latter of which originates from polycyclic aromatic hydrocarbons (PAHs) or materials containing PAHs. The spectra show a broad, complex absorption feature at 4.65 μm, which is well explained by a combination of absorption features of CO ice, CO gas, and XCN, and H I Pfβ emission. The spectra also indicate excess emission at 4.4 μm. The characteristics of the spectra suggest that the object is a massive young stellar object. The XCN feature shows a good correlation with the Brα emission, suggesting that the photolysis by ultraviolet photons plays an important role in the formation of the XCN carriers, part of which are attributed to OCN-. The 4.4 μm emission shows a good correlation with the 3.3 μm PAH emission, providing supporting evidence that it comes from the aromatic C-D stretching vibration. The formation of OCN- is of importance for the formation process of prebiotic matter in the interstellar medium (ISM), while the detection of aromatic C-D emission provides valuable information on the deuteration process of PAHs in the ISM and implications on the hiding site of the missing deuterium in the ISM.

Keywords: interstellar dust; interstellar medium; ice formation; polycyclic aromatic hydrocarbons; young stellar objects
An MHD Modeling of the Successive X2.2 and X9.3 Solar Flares of 2017 September 6

The solar active region 12673 produced two successive X-class flares (X2.2 and X9.3) approximately 3 hr apart in 2017 September. The X9.3 flare was the largest recorded solar flare in Solar Cycle 24. In this study we perform a data-constrained magnetohydrodynamic simulation taking into account the observed photospheric magnetic field to reveal the initiation and dynamics of the X2.2 and X9.3 flares. According to our simulation, the X2.2 flare is first triggered by magnetic reconnection at a local site where at the photosphere the negative polarity intrudes into the opposite-polarity region. This magnetic reconnection expels the innermost field lines upward, beneath which the magnetic flux rope is formed through continuous reconnection with external twisted field lines. Continuous magnetic reconnection after the X2.2 flare enhances the magnetic flux rope, which is lifted up and eventually erupts via the torus instability. This gives rise to the X9.3 flare.

Keywords: magnetohydrodynamical simulations; solar flares; solar magnetic fields; solar active regions
Assessing the Performance of the ADAPT and AFT Flux Transport Models Using In Situ Measurements from Multiple Satellites

The launches of Parker Solar Probe (Parker) and Solar Orbiter (SolO) are enabling a new era of solar wind studies that track the solar wind from its origin at the photosphere, through the corona, to multiple vantage points in the inner heliosphere. A key ingredient for these models is the input photospheric magnetic field map that provides the boundary condition for the coronal portion of many heliospheric models. In this paper, we perform steady-state, data-driven magnetohydrodynamic (MHD) simulations of the solar wind during Carrington rotation 2258 with the Grid GAMERA model. We use the ADAPT and AFT flux transport models and quantitatively assess how well each model matches in situ measurements from Parker, SolO, and Earth. We find that both models reproduce the magnetic field components at Parker quantitatively well. At SolO and Earth, the magnetic field is reproduced relatively well, though not as well as at Parker, and the density is reproduced extremely poorly. The velocity is overpredicted at Parker, but not at SolO or Earth, hinting that the Wang–Sheeley–Arge (WSA) relation, fine-tuned for Earth, misses the deceleration of the solar wind near the Sun. We conclude that AFT performs quantitatively similarly to ADAPT in all cases, and that both models are comparable to a purely WSA heliospheric treatment with no MHD component. Finally, we trace field lines from SolO back to an active region outflow that was observed by Hinode/EIS, and which shows evidence of elevated charge state ratios.

Keywords: solar wind; heliosphere; solar corona
Reflection from Inclined, Relativistic Light Sails

We present a new formula for relativistic reflection of solar radiation from a light sail moving at a velocity v inclined at an arbitrary angle θ, using an elementary two-body analysis. The formula is shown to reduce to the formulas of Euclid, Einstein, and Gjurchinovski in the relevant limits. Our results are of relevance for computing optimal geometries for relativistic light sails.

Keywords: space vehicles; space probes; deep space probes
Prompt Enhancements of Radiation Belt Electrons over a Wide Energy Range Based on Phase Space Density Variations: A Detailed Case Study

Based on Van Allen Probes observations, we report a prompt enhancement event of radiation belt electrons over a wide energy range from tens of keV to multiple meV spanning 2013 January 13-15. During this period, we also observe prolonged moderate substorm activities and intense whistler-mode chorus emissions. To differentiate the underlying mechanisms responsible for this prompt electron enhancement process, we investigate in detail the evolution of electron phase space densities (PSDs) for various values of the first and second adiabatic invariants (μ and K). The results show that tens to hundreds of keV electrons rapidly penetrated to L* < 4 during the substorm period, with the corresponding PSDs increasing by more than 3 orders of magnitude within about 1 day. Comparatively, the PSD enhancements of higher energy electrons are less significant and shift to higher L*. We find that the fast acceleration of hundreds of keV seed electrons to multi-meV electrons may be reasonably attributed to interactions with the concurrent chorus waves. Specifically, the electron PSD increases for μ≥ 300 MeV G-1 become less pronounced as K increases, consistent with the pitch angle dependence of chorus-induced electron energy diffusion at high energies. Our results therefore provide clear observational evidence for the combined effect of substorm-induced injection and chorus wave scattering on the prompt enhancements of radiation belt electrons over a wide energy range within a couple of days.

Keywords: van allen radiation belts; dynamical evolution; plasma physics
An Atlas of Convection in Main-sequence Stars

Convection is ubiquitous in stars and occurs under many different conditions. Here we explore convection in main-sequence stars through two lenses: dimensionless parameters arising from stellar structure and parameters that emerge from the application of mixing length theory. We first define each quantity in terms familiar to both the 1D stellar evolution community and the hydrodynamics community. We then explore the variation of these quantities across different convection zones, different masses, and different stages of main-sequence evolution. We find immense diversity across stellar convection zones. Convection occurs in thin shells, deep envelopes, and nearly spherical cores; it can be efficient or inefficient, rotationally constrained or not, transsonic or deeply subsonic. This atlas serves as a guide for future theoretical and observational investigations by indicating which regimes of convection are active in a given star, and by describing appropriate model assumptions for numerical simulations.

Keywords: stellar physics; stellar evolutionary models; stellar convective zones
Tracing PAH Size in Prominent Nearby Mid-Infrared Environments

We present observations from the First Light Infrared TEst CAMera (FLITECAM) on board the Stratospheric Observatory for Infrared Astronomy, the Spitzer Infrared Array Camera (IRAC), and the Spitzer Infrared Spectrograph SH mode in three well-known photodissociation regions, the reflection nebulae (RNe) NGC 7023 and NGC 2023 and to the southeast of the Orion Bar, which are well suited to probe emission from polycyclic aromatic hydrocarbon molecules (PAHs). We investigate the spatial behavior of the FLITECAM 3.3 μm filter as a proxy for the 3.3 μm PAH band, the integrated 11.2 μm PAH band, and the IRAC 8.0 μm filter as a proxy for the sum of the 7.7 and 8.6 μm PAH bands. The resulting ratios of 11.2/3.3 and IRAC 8.0/11.2 provide an approximate measure of the average PAH size and PAH ionization, respectively. In both RNe, we find that the relative PAH ionization and the average PAH size increase with decreasing distance to the illuminating source. The average PAH sizes derived for NGC 2023 are greater than those found for NGC 7023 at all points. Both results indicate that PAH size is dependent on the radiation field intensity. These results provide additional evidence of a rich carbon-based chemistry driven by the photochemical evolution of the omnipresent PAH molecules within the interstellar medium. In contrast, we did not detect a significant variation in the average PAH size found in the region southeast of the Orion Bar and report a peculiar PAH ionization radial profile.

Keywords: polycyclic aromatic hydrocarbons; reflection nebulae; photodissociation regions; interstellar medium
Probe for Type Ia Supernova Progenitor in Decihertz Gravitational Wave Astronomy

It is generally believed that Type Ia supernovae are thermonuclear explosions of carbon-oxygen white dwarfs (WDs). However, there is currently no consensus regarding the events leading to the explosion. A binary WD (WD-WD) merger is a possible progenitor of Type Ia supernovae. Space-based gravitational wave (GW) detectors with considerable sensitivity in the decihertz range such as the DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) can observe WD-WD mergers directly. Therefore, access to the decihertz band of GWs would enable multi-messenger observations of Type Ia supernovae to determine their progenitors and explosion mechanism. In this paper, we consider the event rate of WD-WD mergers and the minimum detection range to observe one WD-WD merger per year, using a nearby galaxy catalog and the relation between Ia supernovae and their host galaxies. Furthermore, we calculate DECIGO's ability to localize WD-WD mergers and to determine the masses of binary mergers. We estimate that a decihertz GW observatory can detect GWs with amplitudes of h ~ 10-20 [Hz-1/2] at 0.01-0.1 Hz, which is 1000 times higher than the detection limit of DECIGO. Assuming the progenitors of Ia supernovae are merging WD-WD (1 M ⊙ and 0.8 M ⊙), DECIGO is expected to detect 6600 WD-WD mergers within z = 0.08, and identify the host galaxies of such WD-WD mergers within z ~ 0.065 using GW detections alone.

Keywords: gravitational wave astronomy; type ia supernovae
Arecibo Radar Maps of Venus from 1988 to 2020

Over its 57 yr history, the Arecibo telescope was used to produce radar maps of Venus that pioneered our understanding of surface landforms and geologic processes. The best spatial resolution of 1-2 km achievable with the S-band (2380 MHz) transmitter was first used to map the surface in 1988, providing dual-circular polarization images ahead of the Magellan mission. Along with the 1988 observations, high-resolution images from observing runs in 2012, 2015, 2017, and 2020 have been archived with the NASA Planetary Data System to preserve these legacy data sets. We document the data collection and processing methods for the Arecibo Venus data, discuss unique aspects of the delay-Doppler imaging, and derive relative calibration factors linking the final multilook maps and Magellan data. The observations also allow for derivation of the circular polarization ratio and, potentially, the Stokes vector components. These results are particularly relevant for long-term monitoring of the spin rate, surface change detection, and planning for S-band polarimetry from the EnVision orbiter mission.

Keywords: venus; radar astronomy
Ground-based and JWST Observations of SN 2022pul. I. Unusual Signatures of Carbon, Oxygen, and Circumstellar Interaction in a Peculiar Type Ia Supernova

Nebular-phase observations of peculiar Type Ia supernovae (SNe Ia) provide important constraints on progenitor scenarios and explosion dynamics for both these rare SNe and the more common, cosmologically useful SNe Ia. We present observations from an extensive ground- and space-based follow-up campaign to characterize SN 2022pul, a super-Chandrasekhar mass SN Ia (alternatively "03fg-like" SN), from before peak brightness to well into the nebular phase across optical to mid-infrared (MIR) wavelengths. The early rise of the light curve is atypical, exhibiting two distinct components, consistent with SN Ia ejecta interacting with dense carbon-oxygen (C/O)-rich circumstellar material (CSM). In the optical, SN 2022pul is most similar to SN 2012dn, having a low estimated peak luminosity (M B = -18.9 mag) and high photospheric velocity relative to other 03fg-like SNe. In the nebular phase, SN 2022pul adds to the increasing diversity of the 03fg-like subclass. From 168 to 336 days after peak B-band brightness, SN 2022pul exhibits asymmetric and narrow emission from [O I] λ λ6300, 6364 (FWHM ≈ 2000 km s-1), strong, broad emission from [Ca II] λ λ7291, 7323 (FWHM ≈ 7300 km s-1), and a rapid Fe III to Fe II ionization change. Finally, we present the first ever optical-to-MIR nebular spectrum of an 03fg-like SN Ia using data from JWST. In the MIR, strong lines of neon and argon, weak emission from stable nickel, and strong thermal dust emission (with T ≈ 500 K), combined with prominent [O I] in the optical, suggest that SN 2022pul was produced by a white dwarf merger within C/O-rich CSM.

Keywords: supernovae; observational astronomy; white dwarf stars; type ia supernovae
Time-dependent Photoionization Modeling of Warm Absorbers in Active Galactic Nuclei

Warm absorber spectra contain bound-bound and bound-free absorption features seen in the X-ray and UV spectra from many active galactic nuclei. The widths and centroid energies of these features indicate they occur in outflowing gas, and the outflow can affect the gas within the host galaxy. Thus, the warm absorber mass and energy budgets are of great interest. Estimates for these properties depend on models that connect the observed strengths of the absorption features with the density, composition, and ionization state of the absorbing gas. Such models assume that the ionization and heating of the gas come primarily from the strong continuum near the central black hole. They also assume that the various heating, cooling, ionization, and recombination processes are in a time-steady balance. This assumption may not be valid, owing to the intrinsic time variability of the illuminating continuum or other factors that change the cloud environment. This paper presents models for warm absorbers that follow the time dependence of the ionization, temperature, and radiation field in warm absorber gas clouds in response to a changing continuum illumination. We show that the effects of time variability are important over a range of parameter values, that time-dependent models differ from equilibrium models in meaningful ways, and that these effects should be included in models that derive properties of warm absorber outflows.

Keywords: active galactic nuclei; high energy astrophysics; plasma astrophysics; warm ionized medium; time domain astronomy; high time resolution astrophysics; active galaxies; agn host galaxies; seyfert galaxies; astrophysical black holes; diffuse interstellar clouds; photoionization
Pre-impact Albedo Map and Photometric Properties of the (65803) Didymos Asteroid Binary System from DART and Ground-based Data

This study provides a pre-impact map of the albedo of the Double Asteroid Redirection Test (DART) target Dimorphos corrected for all the effects of viewing geometry, as well as an estimate of photometric roughness for the hemisphere imaged by DART. Other photometric properties are derived for the (65803) Didymos binary system based on DART and ground-based measurements obtained at JPL's Table Mountain Observatory. The roughness, geometric albedo, phase curve and phase integral, and single particle phase function are typical of the S-family of asteroids. The major remaining uncertainty lies in the behavior of the phase curve below 7°. These results provide a baseline for comparison with Hera measurements, leading to an understanding of the quantitative effects of the kinetic impactor mitigation strategy.

Keywords: asteroid surfaces; near-earth objects
On the Fraction of X-Ray-weak Quasars from the Sloan Digital Sky Survey

We investigate systematically the X-ray emission from type 1 quasars using a sample of 1825 Sloan Digital Sky Survey non-broad absorption line (non-BAL) quasars with Chandra archival observations. A significant correlation is found between the X-ray-to-optical power-law slope parameter (αOX) and the 2500 Å monochromatic luminosity (L2500Å), and the X-ray weakness of a quasar is assessed via the deviation of its αOX value from that expected from this relation. We demonstrate the existence of a population of non-BAL X-ray-weak quasars, and the fractions of quasars that are X-ray weak by factors of ≥6 and ≥10 are 5.8% ± 0.7% and 2.7% ± 0.5%, respectively. We classify X-ray-weak quasars (X-ray weak by factors of ≥6) into three categories based on their optical spectral features: weak emission-line quasars (WLQs; C IV rest-frame equivalent width < 16 Å), red quasars (Δ(g - i) > 0.2), and unclassified X-ray-weak quasars. The X-ray-weak fraction of ${35}_{-9}^{+12} \% $ within the WLQ population is significantly higher than that within non-WLQs, confirming previous findings that WLQs represent one population of X-ray-weak quasars. The X-ray-weak fraction of ${13}_{-3}^{+5} \% $ within the red quasar population is also considerably higher than that within the normal quasar population. The unclassified X-ray-weak quasars do not have unusual optical spectral features, and their X-ray weakness may be mainly related to quasar X-ray variability.

Keywords: galaxy nuclei; x-ray quasars; active galaxies
Constraining Nuclear Parameters Using Gravitational Waves from f-mode Oscillations in Neutron Stars

Gravitational waves (GWs) emanating from unstable quasi-normal modes in neutron stars (NSs) could be accessible with the improved sensitivity of the current GW detectors or with the next-generation GW detectors and, therefore, can be employed to study the NS interior. Assuming f-mode excitation in isolated pulsars with typical energy of pulsar glitches and considering potential f-mode GW candidates for A+ (upgraded LIGO detectors operating at fifth observing run design sensitivity) and Einstein Telescope (ET), we demonstrate the inverse problem of NS asteroseismology within a Bayesian formalism to constrain the nuclear parameters and NS equation of state (EOS). We describe the NS interior within relativistic mean-field formalism. Taking the example of glitching pulsars, we find that for a single event in A+ and ET, among the nuclear parameters, the nucleon effective mass (m*) within 90% credible interval can be restricted within 10% and 5%, respectively. At the same time, the incompressibility (K) and the slope of the symmetry energy (L) are only loosely constrained. Considering multiple (10) events in A+ and ET, all the nuclear parameters are well constrained, especially m*, which can be constrained to 3% and 2% in A+ and ET, respectively. Uncertainty in the observables of a 1.4 M ⊙ NS such as radius ( ${R}_{1.4{M}_{\odot }}$ ), f-mode frequency ( ${f}_{1.4{M}_{\odot }}$ ), damping time ( ${\tau }_{1.4{M}_{\odot }}$ ), and a few EOS properties including squared speed of sound (c s 2) are also estimated.

Keywords: neutron stars; neutron star cores; gravitational waves; nuclear astrophysics; pulsars; stellar oscillations; asteroseismology