adsabs/SciX_UAT_keywords huggingface dataset:
Prevalence of Thermal Nonequilibrium over an Active Region

Recent observations have shown that besides the characteristic multimillion degree component, the corona also contains a large amount of cool material called coronal rain, whose clumps are 10-100 times cooler and denser than the surroundings and are often organized in larger events, termed showers. Thermal instability (TI) within a coronal loop in a state of thermal nonequilibrium (TNE) is the leading mechanism behind the formation of coronal rain but no investigation on showers exists to date. In this study, we conduct a morphological and thermodynamic multiwavelength study of coronal rain showers observed in an active region (AR) off-limb with IRIS and the Solar Dynamics Observatory, spanning chromospheric to transition region and coronal temperatures. Rain showers were found to be widespread across the AR over the 5.45 hr observing time, with an average length, width, and duration of 27.37 ± 11.95 Mm, 2.14 ± 0.74 Mm, and 35.22 ± 20.35 minutes, respectively. We find a good correspondence between showers and the cooling coronal structures consistent with the TNE-TI scenario, thereby properly identifying coronal loops in the "coronal veil", including the strong expansion at low heights and an almost zero expansion in the corona. This agrees with previous work suggesting that the observed zero expansion in the EUV is due to specific cross-field temperature distribution. We estimate the total number of showers to be 155 ± 40, leading to a TNE volume of 4.56 ± [3.71] × 1028 cm3, i.e., on the same order of the AR volume. This suggests a prevalence of TNE over the AR indicating strongly stratified and high-frequency heating on average.

Keywords: solar coronal heating; solar coronal loops; solar prominences; solar chromosphere; solar transition region
Constraining the Limitations of NEATM-like Models: A Case Study with Near-Earth Asteroid (285263) 1998 QE2

Near-Earth asteroids (NEAs) are a key test bed for investigations into planet formation, asteroid dynamics, and planetary defense initiatives. These studies rely on understanding NEA sizes, albedo distributions, and regolith properties. Simple thermal models are a commonly used method for determining these properties; however, they have inherent limitations owing to the simplifying assumptions they make about asteroid shapes and properties. With the recent collapse of the Arecibo Telescope and a decrease of direct size measurements, as well as future facilities such as LSST and NEO Surveyor coming online soon, these models will play an increasingly important role in our knowledge of the NEA population. Therefore, it is key to understand the limits of these models. In this work we constrain the limitations of simple thermal models by comparing model results to more complex thermophysical models, radar data, and other existing analyses. Furthermore, we present a method for placing tighter constraints on inferred NEA properties using simple thermal models. These comparisons and constraints are explored using the NEA (285263) 1998 QE2 as a case study. We analyze QE2 with a simple thermal model and data from both the NASA IRTF SpeX instrument and NEOWISE mission. We determine an albedo between 0.05 and 0.10 and thermal inertia between 0 and 425J m-2 s-1/2 K-1. We find that overall the simple thermal model is able to well constrain the properties of QE2; however, we find that model uncertainties can be influenced by topography, viewing geometry, and the wavelength range of data used.

Keywords: asteroids; asteroid surfaces; near-earth objects
Stellar Companions to TESS Objects of Interest: A Test of Planet-Companion Alignment

We present a catalog of stellar companions to host stars of Transiting Exoplanet Survey Satellite Objects of Interest (TOIs) identified from a marginalized likelihood ratio test that incorporates astrometric data from the Gaia Early Data Release 3 catalog (EDR3). The likelihood ratio is computed using a probabilistic model that incorporates parallax and proper-motion covariances and marginalizes the distances and 3D velocities of stars in order to identify comoving stellar pairs. We find 172 comoving companions to 170 non-false-positive TOI hosts, consisting of 168 systems with two stars and 2 systems with three stars. Among the 170 TOI hosts, 54 harbor confirmed planets that span a wide range of system architectures. We conduct an investigation of the mutual inclinations between the stellar companion and planetary orbits using Gaia EDR3, which is possible because transiting exoplanets must orbit within the line of sight; thus, stellar companion kinematics can constrain mutual inclinations. While the statistical significance of the current sample is weak, we find that ${73}_{-20}^{+14} \% $ of systems with Kepler-like architectures (R P ≤ 4 R ⊕ and a < 1 au) appear to favor a nonisotropic orientation between the planetary and companion orbits with a typical mutual inclination α of 35° ± 24°. In contrast, ${65}_{-35}^{+20}$ % of systems with close-in giants (P < 10 days and R P > 4 R ⊕) favor a perpendicular geometry (α = 89° ± 21°) between the planet and companion. Moreover, the close-in giants with large stellar obliquities (planet-host misalignment) are also those that favor significant planet-companion misalignment.

Keywords: binary stars; exoplanet dynamics; astrometry; bayesian statistics; hierarchical models
Electric Field Screening in Pair Discharges and Generation of Pulsar Radio Emission

Pulsar radio emission may be generated in pair discharges that fill the pulsar magnetosphere with plasma as an accelerating electric field is screened by freshly created pairs. In this Letter, we develop a simplified analytic theory for the screening of the electric field in these pair discharges and use it to estimate total radio luminosity and spectrum. The discharge has three stages. First, the electric field is screened for the first time and starts to oscillate. Next, a nonlinear phase occurs. In this phase, the amplitude of the electric field experiences strong damping because the field dramatically changes the momenta of newly created pairs. This strong damping ceases, and the system enters a final linear phase, when the electric field can no longer dramatically change pair momenta. Applied to pulsars, this theory may explain several aspects of radio emission, including the observed luminosity, L rad ~ 1028 erg s-1, and the observed spectrum, S ω ~ ω -1.4±1.0.

Keywords: pulsars; neutron stars; radio pulsars; plasma astrophysics; plasma physics; high energy astrophysics
Origins of the Evil Eye: M64's Stellar Halo Reveals the Recent Accretion of an SMC-mass Satellite

M64, often called the "Evil Eye" galaxy, is unique among local galaxies. Beyond its dramatic, dusty nucleus, it also hosts an outer gas disk that counter-rotates relative to its stars. The mass of this outer disk is comparable to the gas content of the Small Magellanic Cloud (SMC), prompting the idea that it was likely accreted in a recent minor merger. Yet, detailed follow-up studies of M64's outer disk have shown no evidence of such an event, leading to other interpretations, such as a "flyby" interaction with the distant diffuse satellite Coma P. We present Subaru Hyper Suprime-Cam observations of M64's stellar halo, which resolve its stellar populations and reveal a spectacular radial shell feature, oriented ~30° relative to the major axis and along the rotation axis of the outer gas disk. The shell is ~45 kpc southeast of M64, while a similar but more diffuse plume to the northwest extends to >100 kpc. We estimate a stellar mass and metallicity for the southern shell of M ⋆ = 1.80 ± 0.54 × 108 M ⊙ and [M/H] = -1.0, respectively, and a similar mass of 1.42 ± 0.71 × 108 M ⊙ for the northern plume. Taking into account the accreted material in M64's inner disk, we estimate a total stellar mass for the progenitor satellite of M ⋆,prog ≃ 5 × 108 M ⊙. These results suggest that M64 is in the final stages of a minor merger with a gas-rich satellite strikingly similar to the SMC, in which M64's accreted counter-rotating gas originated, and which is responsible for the formation of its dusty inner star-forming disk.

Keywords: galaxy stellar halos; galaxy mergers; stellar populations
A Sensitive Search for Supernova Emission Associated with the Extremely Energetic and Nearby GRB 221009A

We report observations of the optical counterpart of the long gamma-ray burst GRB 221009A. Due to the extreme rarity of being both nearby (z = 0.151) and highly energetic (E γ,iso ≥ 1054 erg), GRB 221009A offers a unique opportunity to probe the connection between massive star core collapse and relativistic jet formation across a very broad range of γ-ray properties. Adopting a phenomenological power-law model for the afterglow and host galaxy estimates from high-resolution Hubble Space Telescope imaging, we use Bayesian model comparison techniques to determine the likelihood of an associated supernova (SN) contributing excess flux to the optical light curve. Though not conclusive, we find moderate evidence (K Bayes = 101.2) for the presence of an additional component arising from an associated SN, SN 2022xiw, and find that it must be substantially fainter (<67% as bright at the 99% confidence interval) than SN 1998bw. Given the large and uncertain line-of-sight extinction, we attempt to constrain the SN parameters (M Ni, M ej, and E KE) under several different assumptions with respect to the host galaxy's extinction. We find properties that are broadly consistent with previous GRB-associated SNe: M Ni = 0.05-0.25 M ⊙, M ej = 3.5-11.1 M ⊙, and E KE = (1.6-5.2) × 1052 erg. We note that these properties are weakly constrained due to the faintness of the SN with respect to the afterglow and host emission, but we do find a robust upper limit on M Ni of M Ni < 0.36 M ⊙. Given the tremendous range in isotropic gamma-ray energy release exhibited by GRBs (seven orders of magnitude), the SN emission appears to be decoupled from the central engine in these systems.

Keywords: core-collapse supernovae; gamma-ray bursts; relativistic jets
Propionamide (C2H5CONH2): The Largest Peptide-like Molecule in Space

Peptide bonds, as the molecular bridges that connect amino acids, are crucial to the formation of proteins. Searches and studies of molecules with embedded peptide-like bonds are thus important for the understanding of protein formation in space. Here we report the first tentative detection of propionamide (C2H5CONH2), the largest peptide-like molecule detected in space toward Sagittarius B2(N1) at a position called N1E that is slightly offset from the continuum peak. New laboratory measurements of the propionamide spectrum were carried out in the 9-461 GHz range, which provide good opportunity to check directly for the transition frequencies of detected interstellar lines of propionamide. Our observing result indicates that propionamide emission comes from the warm, compact cores in Sagittarius B2, in which massive protostellars are forming. The column density of propionamide toward Sgr B2(N1E) was derived to be 1.5 × 1016 cm-2, which is three-fifths of that of acetamide, and one-nineteenth of that of formamide. This detection suggests that large peptide-like molecules can form and survive during star-forming process and may form more complex molecules in the interstellar medium (ISM). The detection of propionamide bodes well for the presence of polypeptides, as well as other complex prebiotic molecules in the ISM.

Keywords: astrochemistry; spectral line identification; spectroscopy
ALMA Observations of the Asymmetric Dust Disk around DM Tau

We report an analysis of the dust disk around DM Tau, newly observed with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3 mm. The ALMA observations with high sensitivity (8.4 μJy beam-1) and high angular resolution (35 mas, 5.1 au) detect two asymmetries on the ring at r ∼ 20 au. They could be two vortices in early evolution, the destruction of a large-scale vortex, or double continuum emission peaks with different dust sizes. We also found millimeter emissions with ∼50 μJy (a lower-limit dust mass of 0.3 MMoon) inside the 3 au ring. To characterize these emissions, we modeled the spectral energy distribution (SED) of DM Tau using a Monte Carlo radiative transfer code. We found that an additional ring at r = 1 au could explain both the DM Tau SED and the central point source. The disk midplane temperature at the 1 au ring calculated in our modeling is less than the typical water sublimation temperature of 150 K, prompting the possibility of forming small icy planets there.

Keywords: protoplanetary disks
The Spin-Orbit Misalignment of TOI-1842b: The First Measurement of the Rossiter-McLaughlin Effect for a Warm Sub-Saturn around a Massive Star

The mechanisms responsible for generating spin-orbit misalignments in exoplanetary systems are still not fully understood. It is unclear whether these misalignments are related to the migration of hot Jupiters or are a consequence of general star and planet formation processes. One promising method to address this question is to constrain the distribution of spin-orbit angle measurements for a broader range of planets beyond hot Jupiters. In this work, we present the sky-projected obliquity ( $\lambda =-68\buildrel{\circ}\over{.} {1}_{-14.7}^{+21.2}$ ) for the warm sub-Saturn TOI-1842b, obtained through a measurement of the Rossiter-McLaughlin effect using WIYN/NEID. From this, we determine the resulting 3D obliquity (ψ) to be $\psi =73\buildrel{\circ}\over{.} {3}_{-12.9}^{+16.3}$ . As the first spin-orbit angle determination made for a sub-Saturn-mass planet around a massive ( M * = 1.45 M ☉) star, our result presents an opportunity to examine the orbital geometries for new regimes of planetary systems. When combined with archival measurements, our observations of TOI-1842b support the hypothesis that the previously established prevalence of misaligned systems around hot, massive stars may be driven by planet-planet dynamical interactions. In massive stellar systems, multiple gas giants are more likely to form and can then dynamically interact with each other to excite spin-orbit misalignments.

Keywords: hot jupiters; exoplanet dynamics; exoplanet formation; transits; radial velocity; planet formation; exoplanets
γ-Ray Emission from Classical Nova V392 Per: Measurements from Fermi and HAWC

This paper reports on the γ-ray properties of the 2018 Galactic nova V392 Per, spanning photon energies ~0.1 GeV-100 TeV by combining observations from the Fermi Gamma-ray Space Telescope and the HAWC Observatory. As one of the most rapidly evolving γ-ray signals yet observed for a nova, GeV γ-rays with a power-law spectrum with an index Γ = 2.0 ± 0.1 were detected over 8 days following V392 Per's optical maximum. HAWC observations constrain the TeV γ-ray signal during this time and also before and after. We observe no statistically significant evidence of TeV γ-ray emission from V392 Per, but present flux limits. Tests disfavor the extension of the Fermi Large Area Telescope spectrum to energies above 5 TeV by 2 standard deviations (95%) or more. We fit V392 Per's GeV γ-rays with hadronic acceleration models, incorporating optical observations, and compare the calculations with HAWC limits.

Keywords: novae; cataclysmic variable stars; white dwarf stars; gamma-rays; binary stars
Examining the Secondary Product Origin of Cosmic-Ray Positrons with the Latest AMS-02 Data

Measurements of cosmic-ray (CR) positron fractions by PAMELA and other experiments have found an excess above 10 GeV relative to the standard predictions for secondary production in the interstellar medium. Although the excess has been mainly suggested to arise from some primary sources of positrons (such as pulsars and or annihilating dark matter particles), the almost constant flux ratio of ${e}^{+}/\bar{p}$ argues for an alternative possibility that the excess positrons and antiprotons up to the highest energies are secondary products generated in hadronic interactions. Recently, Yang & Aharonian revisited this possibility by assuming the presence of an additional population of CR nuclei sources. Here we examine this secondary product scenario using the DRAGON code, where the radiative loss of positrons is taken into account consistently. We confirm that the CR proton spectrum and the antiproton data can be explained by assuming the presence of an additional population of CR sources. However, the corresponding positron spectrum deviates from the measured data significantly above 100 GeV due to strong radiative cooling. This suggests that although hadronic interactions can explain the antiproton data, the corresponding secondary positron flux is still not enough to account for the Alpha Magnetic Spectrometer data. Hence the contribution from some primary positron sources, such as pulsars or dark matter, is nonnegligible.

Keywords: galactic cosmic rays; secondary cosmic rays
Clustering of Local Group Distances: Publication Bias or Correlated Measurements? VII. A Distance Framework out to 100 Mpc

We consider the body of published distance moduli to the Fornax and Coma galaxy clusters, with specific emphasis on the period since 1990. We have carefully homogenized our final catalogs of distance moduli onto the distance scale established in the previous papers in this series. We assessed systematic differences associated with the use of specific tracers and consequently discarded results based on application of the Tully-Fisher relation and of globular cluster and planetary nebula luminosity functions. We recommend "best" weighted relative distance moduli for the Fornax and Coma clusters with respect to the Virgo cluster benchmark of ${\rm{\Delta }}(m-M{)}_{0}^{\mathrm{Fornax}-\mathrm{Virgo}}=0.18\pm 0.28$ mag and ${\rm{\Delta }}(m-M{)}_{0}^{\mathrm{Coma}-\mathrm{Virgo}}=3.75\pm 0.23$ mag. The set of weighted mean distance moduli (distances) we derived as most representative of the clusters' distances is

m - M0 Fornax = 31.41 ± 0.15 mag (D = 19.1 -1.2 +1.4 Mpc) and = 31.21 ± 0.28 mag (D = 17.5 -2.2 +2.4 Mpc), m - M0 Coma = 34.99 ± 0.38 mag (D = 99.5 -15.9 +19.0 Mpc) and = 34.78 ± 0.27 mag (D = 90.4 -10.6 +11.9 Mpc)

where the first distance modulus for each cluster is the result of our analysis of the direct, absolute distance moduli, while the second modulus is based on distance moduli relative to the Virgo cluster. While the absolute and relative distance moduli for both clusters are mutually consistent within the uncertainties, the relative distance moduli yield shorter absolute distances by ∼1σ. It is unclear what may have caused this small difference for both clusters; lingering uncertainties in the underlying absolute distance scale appear to have given rise to a systematic uncertainty of the order of 0.20 mag.

Keywords: astronomical reference materials; astronomy databases; distance measure; galaxy distances; coma cluster
The Eroding Disk of AU Mic

We report Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph imaging of AU Mic's debris disk from 2017 and archival data. Outward motion of the features in the southeast arm continues. At least three features have reached or exceeded projected escape velocity in the past decade, yielding a combined feature mass-loss rate of ∼1.2 × 10-7 MEarth yr-1, or ∼1.2 × 10-13 M⊙ yr-1, ∼10% of AU Mic's stellar wind mass-loss rate, and similar to the ratio of coronal mass ejection mass loss to the stellar wind mass-loss rate. We confirm the 2018 finding of feature height changes for one feature (B/SE4), but the HST data are too sparse to compare (yet) with the stellar activity cycle. Detection of what appears to be a chain of features in a second system suggests that the disk of AU Mic is not unique, although a larger sample of disks is required to quantify how common the phenomenon is.

Keywords: stellar activity; debris disks; m dwarf stars
Prospects of Gravitational Wave Detections from Common Envelope Evolution with LISA

Understanding common envelope (CE) evolution is an outstanding problem in binary evolution. Although the CE phase is not driven by gravitational wave (GW) emission, the inspiraling binary emits GWs that passively trace CE dynamics. Detecting this GW signal would provide direct insight into gas-driven physics. Even a non-detection might offer invaluable constraints. We investigate the prospects of detection of a Galactic CE by LISA. While the dynamical phase of the CE is likely sufficiently loud for detection, it is short and thus rare. We focus instead on the self-regulated phase that proceeds on a thermal timescale. Based on population-synthesis calculations and the (unknown) signal duration in the LISA band, we expect ~0.1-100 sources in the Galaxy during the mission duration. We map the GW observable parameter space of frequency fGW and its derivative ${\dot{f}}_{\mathrm{GW}}$ , remaining agnostic on the specifics of the inspiral and find that signals with signal-to-noise ratios > 10 are possible if the CE stalls at separations such that fGW ≳ 2 × 10-3 Hz. We investigate the possibility of misidentifying the signal with other known sources. If the second derivative ${\ddot{f}}_{\mathrm{GW}}$ can also be measured, the signal can be distinguished from other sources using a GW braking index. Alternatively, coupling LISA with electromagnetic observations of peculiar red giant stars and/or infrared and optical transients, might allow for the disentangling of a Galactic CE from other Galactic and extragalactic GW sources.

Keywords: common envelope binary stars; common envelope evolution; gravitational wave astronomy; binary stars; interacting binary stars
Investigating Cosmological Models and the Hubble Tension Using Localized Fast Radio Bursts

We use the dispersion measure (DM) and redshift measurements of 24 localized fast radio bursts (FRBs) to compare cosmological models and investigate the Hubble tension. Setting a flat prior on the DM contribution from the Milky Way's halo, ${\mathrm{DM}}_{\mathrm{halo}}^{\mathrm{MW}}\in [5,\,80]\,\mathrm{pc}\,{\mathrm{cm}}^{-3}$ , the best fit for flat ΛCDM is obtained with a Hubble constant ${H}_{0}={95.8}_{-9.2}^{+7.8}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ and a median matter density Ωm ≈ 0.66. The best fit for the R h = ct universe is realized with ${H}_{0}={94.2}_{-6.2}^{+5.6}\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{Mpc}}^{-1}$ . We emphasize that the H 0 measurement depends sensitively on the ${\mathrm{DM}}_{\mathrm{halo}}^{\mathrm{MW}}$ prior. Since flat ΛCDM has one more free parameter, R h = ct is favored by the Bayesian Information Criterion (BIC) with a likelihood of ~73% versus ~27%. Through simulations, we find that if the real cosmology is ΛCDM, a sample of ~1150 FRBs in the redshift range 0 < z < 3 would be sufficient to rule out R h = ct at a 3σ confidence level, while ~550 FRBs would be necessary to rule out ΛCDM if the real cosmology is instead R h = ct. The required sample sizes are different, reflecting the fact that the BIC imposes a severe penalty on the model with more free parameters. We further adopt a straightforward method of deriving an upper limit to H 0, without needing to consider the poorly known probability distribution of the DM contributed by the host galaxy. The theoretical DM contribution from the intergalactic medium (DMIGM) at any z is proportional to H 0. Thus, requiring the extragalactic DMext to be larger than DMIGM delimits H 0 to the upside. Assuming flat ΛCDM, we have H 0 < 89.0 km s-1 Mpc-1 at a 95% confidence level.

Keywords: cosmological parameters; observational cosmology; cosmological models; radio transient sources