adsabs/SciX_UAT_keywords huggingface dataset:
A Two Carrier Families Spectral Profile Model for Anomalous Microwave Emission

We model anomalous microwave emission (AME) spectral profiles from 14 diverse galactic and extragalactic sources. The spectral profile model is an analytic representation of a quantum mechanical model for symmetric top rotational emission. The observed spectral shapes are well fit by superposing two model profiles originating from two distinct carrier families. Each family is composed of numerous, comparably abundant isomers of a parent carrier. The isomers have similar rotational constants, thereby producing continuous, versus resolved line, spectra that are slightly broader than the parent profiles. Ten observations are fit with comparable peak height and peak frequency ratios for the two carrier families, suggesting that AME arises from common carriers. One observation is fit using a single family, attributed to photodissociation of the less stable, smaller molecules for the missing family. Three observations are fit by combining two frequency-shifted model spectra, indicating multiple sources along their sight lines. The derived rotational constants for the two parent carriers are well determined because their rotational temperature is well characterized for the LDN 1622 dark cloud AME source. The rotational constants are consistent with the C36 and C60 fullerenes as the parent carriers. We use a Monte Carlo simulation of fullerene hydrogenation to understand the origins of source variability in the AME model fits. Other potential carriers, polycyclic aromatic hydrocarbons and very small grains, cannot be excluded; however, we find that fulleranes are also viable carriers because their aromatic cages are extremely stable to photodissociation, and their data-derived sizes suggest C36 and C60 parent fullerenes.

Keywords: radio sources; radio spectroscopy; molecular spectroscopy; theoretical models; astronomy data modeling
Stellar Loci. VII. Photometric Metallicities of 5 Million FGK Stars Based on GALEX GR6+7 AIS and Gaia EDR3

We combine photometric data from GALEX GR6+7 All-Sky Imaging Survey and Gaia Early Data Release 3 with stellar parameters from the SAGA and PASTEL catalogs to construct high-quality training samples for dwarfs (0.4 < BP ‑ RP < 1.6) and giants (0.6 < BP ‑ RP < 1.6). We apply careful reddening corrections using empirical temperature- and extinction-dependent extinction coefficients. Using the two samples, we establish a relationship between stellar loci (near-ultraviolet (NUV)‑BP versus BP ‑ RP colors), metallicity, and M G . For a given BP ‑ RP color, a 1 dex change in [Fe/H] corresponds to an approximately 1 magnitude change in NUV ‑ BP color for solar-type stars. These relationships are employed to estimate metallicities based on NUV ‑ BP, BP ‑ RP, and M G . Thanks to the strong metallicity dependence in the GALEX NUV band, our models enable a typical photometric-metallicity precision of approximately σ [Fe/H] = 0.11 dex for dwarfs and σ [Fe/H] = 0.17 dex for giants, with an effective metallicity range extending down to [Fe/H] = ‑3.0 for dwarfs and [Fe/H] = ‑4.0 for giants. We also find that the NUV-band-based photometric-metallicity estimate is not as strongly affected by carbon enhancement as previous photometric techniques. With the GALEX and Gaia data, we have estimated metallicities for about 5 million stars across almost the entire sky, including approximately 4.5 million dwarfs and 0.5 million giants. This work demonstrates the potential of the NUV band for estimating photometric metallicities, and sets the groundwork for utilizing the NUV data from space telescopes such as the upcoming Chinese Space Station Telescope.

Keywords: fundamental parameters of stars; galaxy stellar content; astronomy data analysis; metallicity; near ultraviolet astronomy
CO Line Emission Surfaces and Vertical Structure in Midinclination Protoplanetary Disks

High spatial resolution CO observations of midinclination (≈30°-75°) protoplanetary disks offer an opportunity to study the vertical distribution of CO emission and temperature. The asymmetry of line emission relative to the disk major axis allows for a direct mapping of the emission height above the midplane, and for optically thick, spatially resolved emission in LTE, the intensity is a measure of the local gas temperature. Our analysis of Atacama Large Millimeter/submillimeter Array archival data yields CO emission surfaces, dynamically constrained stellar host masses, and disk atmosphere gas temperatures for the disks around the following: HD 142666, MY Lup, V4046 Sgr, HD 100546, GW Lup, WaOph 6, DoAr 25, Sz 91, CI Tau, and DM Tau. These sources span a wide range in stellar masses (0.50-2.10 M ⊙), ages (~0.3-23 Myr), and CO gas radial emission extents (≈200-1000 au). This sample nearly triples the number of disks with mapped emission surfaces and confirms the wide diversity in line emitting heights (z/r ≈ 0.1 to ≳0.5) hinted at in previous studies. We compute the radial and vertical CO gas temperature distributions for each disk. A few disks show local temperature dips or enhancements, some of which correspond to dust substructures or the proposed locations of embedded planets. Several emission surfaces also show vertical substructures, which all align with rings and gaps in the millimeter dust. Combining our sample with literature sources, we find that CO line emitting heights weakly decline with stellar mass and gas temperature, which, despite large scatter, is consistent with simple scaling relations. We also observe a correlation between CO emission height and disk size, which is due to the flared structure of disks. Overall, CO emission surfaces trace ≈2-5× gas pressure scale heights (Hg) and could potentially be calibrated as empirical tracers of Hg.

Keywords: protoplanetary disks; planet formation; co line emission; high angular resolution
WISE/NEOWISE Multiepoch Imaging of the Potentially Geminid-related Asteroids: (3200) Phaethon, 2005 UD, and 1999 YC

We present space-based thermal infrared observations of the presumably Geminid-associated asteroids: (3200) Phaethon, 2005 UD, and 1999 YC using Wide-field Infrared Survey Explorer/Near-Earth Object WISE. The images were taken at the four wavelength bands 3.4 μm (W1), 4.6 μm (W2), 12 μm (W3), and 22 μm (W4). We find no evidence of lasting mass loss in the asteroids over the decadal multiepoch data sets. We set an upper limit to the mass-loss rate in dust of Q dust ≲ 2 kg s-1 for Phaethon and ≲0.1 kg s-1 for both 2005 UD and 1999 YC, respectively, with little dependency over the observed heliocentric distances of R h = 1.0-2.3 au. For Phaethon, even if the maximum mass loss was sustained over the 1000(s) yr dynamical age of the Geminid stream, it is more than two orders of magnitude too small to supply the reported stream mass (1013-14 kg). The Phaethon-associated dust trail (Geminid stream) is not detected at R h = 2.3 au, corresponding to an upper limit on the optical depth of τ < 7 × 10-9. Additionally, no comoving asteroids with radii r e < 650 m were found. The DESTINY+ dust analyzer would be capable of detecting several of the 10 μm sized interplanetary dust particles when at far distances (≳50,000 km) from Phaethon. From 2005 UD, if the mass-loss rate lasted over the 10,000 yr dynamical age of the Daytime Sextantid meteoroid stream, the mass of the stream would be ~1010 kg. The 1999 YC images showed neither the related dust trail (the optical depth τ < 2 × 10-8) nor comoving objects with radii r e < 170 m at R h = 1.6 au. Estimated physical parameters from these limits do not explain the production mechanism of the Geminid meteoroid stream. Lastly, to explore the origin of the Geminids, we discuss the implications for our data in relation to the possibly sodium-driven perihelion activity of Phaethon.

Keywords: meteor streams; near-earth objects; meteoroids
Revisiting the Spectral Features of Ellerman Bombs and UV Bursts. I. Radiative Hydrodynamic Simulations

Ellerman bombs (EBs) and UV bursts are both small-scale solar activities that occur in active regions. They are now believed to form at different heights in the lower atmosphere. In this paper, we use one-dimensional radiative hydrodynamic simulations to calculate various line profiles in response to heating in different atmospheric layers. We confirm that heating in the upper photosphere to the lower chromosphere can generate spectral features of typical EBs, while heating in the mid to upper chromosphere can generate spectral features of typical UV bursts. The intensity evolution of the Hα line wing in EBs shows a rise-plateau pattern, while that of the Si IV 1403 Å line center in UV bursts shows a rise-fall pattern. However, the predicted enhancement of the FUV continuum near 1400 Å for EBs is rarely reported and requires further observations to check it. With two heating sources or an extended heating source in the atmosphere, both EB and UV burst features could be reproduced simultaneously.

Keywords: solar activity; solar photosphere; solar chromosphere; radiative transfer simulations
Effective Self-interaction of Dark Matter from Gravitational Scattering

I show that gravitational scattering of dark matter objects of mass ~104 M ⊙ and speeds of ~10 km s-1, provides the cross section per unit mass required in self-interacting dark matter models that alleviate the small-scale structure challenges to the collisionless cold dark matter model. For primordial objects of mass 104 M 4 M ⊙, moving at the velocity dispersion characteristic of dwarf galaxies, 10v 1 km s-1, the cross section per unit mass for gravitational scattering is $\sim 10\,({M}_{4}/{v}_{1}^{4})\,{\mathrm{cm}}^{2}\,{{\rm{g}}}^{-1}$ . The steep decline in interaction with increasing velocity explains why self-interaction is not evident in data on massive galaxies and clusters of galaxies.

Keywords: cold dark matter
Untangling Magnetic Complexity in Protoplanetary Disks with the Zeeman Effect

With the recent advent of circular polarization capabilities at the Atacama Large Millimeter/submillimeter Array (ALMA), Zeeman effect measurements of spectral lines are now possible as a means to directly probe line-of-sight magnetic fields in protoplanetary disks (PPDs). We present a modeling study that aims to guide physical interpretation of these anticipated observations. Using a fiducial density structure based on a typical ringed disk, we simulate line emission for the hyperfine components of the CN J = 1-0 transition with the POLARIS radiative transfer code. Since the expected magnetic field and typical CN distribution in PPDs remain largely unconstrained, we produce models with several different configurations. Corresponding integrated Stokes I and V profiles and 0.4 km s-1 resolution, 1″ beam convolved channel maps are presented. We demonstrate that the emission signatures from toroidally dominated magnetic fields are distinguishable from vertically dominated magnetic field based on channel map morphology. Due to line-of-sight and beam cancellation effects, disks with toroidal ${\boldsymbol{B}}$ -field configurations result in significantly diminished Stokes V emission. Complex magnetic fields therefore render the traditionally used method for inferring line-of-sight magnetic field strengths (i.e., fitting the derivative of the Stokes I to the Stokes V profile) ambiguous, since a given intrinsic field strength can yield a variety of Stokes V amplitudes depending on the magnetic field geometry. In addition, gas gaps can create structure in the integrated Stokes V profile that might mimic magnetic substructure. This method should therefore be applied with caution in PPD environments and can only confidently be used as a measure of magnetic field strength if the disk's magnetic field configuration is well understood.

Keywords: protoplanetary disks; magnetic fields; astrochemistry
Orbital Motion, Variability, and Masses in the T Tauri Triple System

We present results from adaptive optics imaging of the T Tauri triple system obtained at the Keck and Gemini Observatories in 2015-2019. We fit the orbital motion of T Tau Sb relative to Sa and model the astrometric motion of their center of mass relative to T Tau N. Using the distance measured by Gaia, we derived dynamical masses of ${M}_{\mathrm{Sa}}=2.05\pm 0.14$ M⊙ and MSb = 0.43 ± 0.06 ${M}_{\odot }$ . The precision in the masses is expected to improve with continued observations that map the motion through a complete orbital period; this is particularly important as the system approaches periastron passage in 2023. Based on published properties and recent evolutionary tracks, we estimate a mass of ∼2 M⊙ for T Tau N, suggesting that T Tau N is similar in mass to T Tau Sa. Narrowband infrared photometry shows that T Tau N remained relatively constant between late 2017 and early 2019 with an average value of K = 5.54 ± 0.07 mag. Using T Tau N to calibrate relative flux measurements since 2015, we found that T Tau Sa varied dramatically between 7.0 and 8.8 mag in the K band over timescales of a few months, while T Tau Sb faded steadily from 8.5 to 11.1 mag in the K band. Over the 27 yr orbital period of the T Tau S binary, both components have shown 3-4 mag of variability in the K band, relative to T Tau N.

Keywords: multiple stars; binary stars
Disentangling the AGN and Star formation Contributions to the Radio-X-Ray Emission of Radio-loud Quasars at 1 < Z < 2

We constrain the emission mechanisms responsible for the prodigious electromagnetic output generated by active galactic nuclei (AGNs) and their host galaxies with a novel state-of-the-art AGN radio-to-X-ray spectral energy distribution model fitting code (ARXSED). ARXSED combines multiple components to fit the spectral energy distributions (SEDs) of AGNs and their host galaxies. Emission components include radio structures such as lobes and jets, infrared emission from the AGN torus, visible-to-X-ray emission from the accretion disk, and radio-to-ultraviolet emission from the host galaxy. Applying ARXSED to the radio SEDs of 20 3CRR quasars at 1 < z < 2 verifies the need for more than a simple power law when compact radio structures are present. The nonthermal emission contributes 91%-57% of the observed-frame 1.25 mm to 850 μm flux, and this component must be accounted for when using these wavelengths to estimate star formation properties. We predict the presence of strong radio-linked X-ray emission in more than half the sample sources. ARXSED estimates median (and the associated first and third quartile ranges) BH mass of ${2.9}_{1.7}^{6.0}\times {10}^{9}\,{M}_{\odot }$ , logarithm of Eddington ratio of $-{1.0}_{-1.2}^{-0.6}$ , and spin of ${0.98}_{0.94}^{0.99}$ for our sample. The inferred AGN torus and accretion disk parameters agree with those estimated from spectroscopic analyses of similar samples in the literature. We present the median intrinsic SED of the luminous radio-loud quasars at 1 < z ≲ 2; this SED represents a significant improvement in the way each component is modeled.

Keywords: radio galaxies; active galactic nuclei; quasars; agn host galaxies; radio loud quasars; spectral energy distribution
Deciphering the Slow-rise Precursor of a Major Coronal Mass Ejection

Coronal mass ejections are explosive plasma phenomena prevalently occurring on the Sun and probably on other magnetically active stars. However, how their pre-eruptive configuration evolves toward the main explosion remains elusive. Here, based on comprehensive observations of a long-duration precursor in an event on 2012 March 13, we determine that the heating and slow rise of the pre-eruptive hot magnetic flux rope (MFR) are achieved through a precursor reconnection located above cusp-shaped high-temperature precursor loops. It is observed that the hot MFR threads are built up continually, with their middle initially showing an "M" shape and then being separated from the cusp of precursor loops, causing the slow rise of the entire MFR. The slow rise, in combination with the thermal-dominated hard X-ray source concentrated at the top of the precursor loops, shows that the precursor reconnection is much weaker than the flare reconnection of the main eruption. We also perform a 3D magnetohydrodynamics simulation that reproduces the early evolution of the MFR transiting from the slow to fast rise. It is revealed that the magnetic tension force pertinent to "M"-shaped threads drives the slow rise, which, however, evolves into a magnetic pressure gradient-dominated regime responsible for the rapid acceleration eruption.

Keywords: solar coronal mass ejections; solar magnetic reconnection; solar flares; magnetohydrodynamics
Kilonova and Optical Afterglow from Binary Neutron Star Mergers. I. Luminosity Function and Color Evolution

In the first work of this series, we adopt a GW170817-like viewing-angle-dependent kilonova model and the standard afterglow model with a light-curve distribution based on the properties of cosmological short gamma-ray burst afterglows to simulate the luminosity functions and color evolution of both kilonovae and optical afterglow emissions from binary neutron star (BNS) mergers. We find that ~10% of the nearly-on-axis afterglows are brighter than the associated kilonovae at the peak time. These kilonovae would be significantly polluted by the associated afterglow emission. Only at large viewing angles with $\sin {\theta }_{{\rm{v}}}\gtrsim 0.20$ , the electromagnetic signals of most BNS mergers would be kilonova-dominated and some off-axis afterglows may emerge at ~5-10 days after the mergers. At a brightness dimmer than ~23-24 mag, according to their luminosity functions, the number of afterglows is much larger than that of kilonovae. Because the search depth of the present survey projects is <22 mag, the number of afterglow events that are detected via serendipitous observations would be much higher than that of kilonova events, consistent with the current observations. For the foreseeable survey projects (e.g., Mephisto, WFST, and LSST), whose search depths can reach ≳23-24 mag, the detection rate of kilonovae could have the same order of magnitude as afterglows. We also find that it may be difficult to use the fading rate in a single band to directly identify kilonovae and afterglows among various fast-evolving transients by serendipitous surveys. However, the color evolution between the optical and infrared bands can identify them because the color evolution patterns of these phenomena are unique compared with those of other fast-evolving transients.

Keywords: gravitational waves; neutron stars; gamma-ray bursts
Transition Region Contribution to AIA Observations in the Context of Coronal Heating

We investigate the ratio of coronal and transition region intensity in coronal loops observed by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO). Using Enthalpy-based Thermal Evolution of Loops (EBTEL) hydrodynamic simulations, we model loops with multiple lengths and energy fluxes heated randomly by events drawn from power-law distributions with different slopes and minimum delays between events to investigate how each of these parameters influences observable loop properties. We generate AIA intensities from the corona and transition region for each realization. The variations within and between models generated with these different parameters illustrate the sensitivity of narrowband imaging to the details of coronal heating. We then analyze the transition region and coronal emission from a number of observed active regions and find broad agreement with the trends in the models. In both models and observations, the transition region brightness is significant, often greater than the coronal brightness in all six "coronal" AIA channels. We also identify an inverse relationship, consistent with heating theories, between the slope of the differential emission measure (DEM) coolward of the peak temperature and the observed ratio of coronal to transition region intensity. These results highlight the use of narrowband observations and the importance of properly considering the transition region in investigations of coronal heating.

Keywords: solar extreme ultraviolet emission; solar coronal loops; solar transition region; solar electromagnetic emission; solar observatories; astronomical models; astronomy data modeling; observational astronomy
Intriguing Plasma Composition Pattern in a Solar Active Region: A Result of Nonresonant Alfvén Waves?

The plasma composition of the solar corona is different from that of the solar photosphere. Elements that have a low first ionization potential (FIP) are preferentially transported to the corona and therefore show enhanced abundances in the corona compared to the photosphere. The level of enhancement is measured using the FIP bias parameter. In this work, we use data from the EUV Imaging Spectrometer on Hinode to study the plasma composition in an active region following an episode of significant new flux emergence into the preexisting magnetic environment of the active region. We use two FIP bias diagnostics: Si X 258.375 Å/S X 264.233 Å (temperature of approximately 1.5 MK) and Ca XIV 193.874 Å/Ar XIV 194.396 Å (temperature of approximately 4 MK). We observe slightly higher FIP bias values with the Ca/Ar diagnostic than Si/S in the newly emerging loops, and this pattern is much stronger in the preexisting loops (those that had been formed before the flux emergence). This result can be interpreted in the context of the ponderomotive force model, which proposes that the plasma fractionation is generally driven by Alfvén waves. Model simulations predict this difference between diagnostics using simple assumptions about the wave properties, particularly that the fractionation is driven by resonant/nonresonant waves in the emerging/preexisting loops. We propose that this results in the different fractionation patterns observed in these two sets of loops.

Keywords: solar active regions; solar abundances
Search for GeV Gamma-Ray Emission from Possible TeV-bright Red Dwarfs with Fermi-LAT

Red dwarfs have been suggested to be among the possible astrophysical species accelerating particles and emitting TeV γ-rays. In an effort to search for the GeV γ-ray counterparts of the suggested TeV emission from eight red dwarfs, we analyze the 0.2–500 GeV γ-ray emission of the regions covering them, exploiting the ∼13.6 yr Pass 8 data from the Fermi Large Area Telescope (LAT). A GeV γ-ray emission excess with a significance of 3.8σ is detected in the direction of the red dwarf V962 Tau. This emission contains V962 Tau in a 1σ error radius and is independent of the catalog source. However, the stellar flare scenario can hardly explain the total energy and lightcurve (LC) derived from the γ-ray emission in view of the spectral analysis. We also analyze the LCs in the positions of the eight red dwarfs, and no time bin with a significance >5σ is found. Therefore, no significant emission from the red dwarfs could be concluded to have been detected by Fermi-LAT.

Keywords: gamma-rays; stellar flares; m dwarf stars
Influence of the Bounds of the Hyperparameters on the Reconstruction of the Hubble Constant with the Gaussian Process

The cosmological model-independent method known as the Gaussian process (GP) has been widely used in the reconstruction of the Hubble constant H0, and the hyperparameters inside GP influence the reconstructed result derived from GP. Different hyperparameters inside GP are used in the constraint of H0 derived from GP with observational Hubble parameter H(z) data, and the influence of the hyperparameters inside GP on the reconstruction of H0 with GP is discussed. The discussion about the hyperparameters inside GP and the forecasts for future data show that the consideration of the lower and upper bounds on the GP's hyperparameters are necessary in order to get an extrapolated result of H0 from GP reliably and robustly.

Keywords: hubble constant; observational cosmology; astronomy data analysis; computational methods