adsabs/SciX_UAT_keywords huggingface dataset:
The Observational Uncertainty of Coronal Hole Boundaries in Automated Detection Schemes

Coronal holes are the observational manifestation of the solar magnetic field open to the heliosphere and are of pivotal importance for our understanding of the origin and acceleration of the solar wind. Observations from space missions such as the Solar Dynamics Observatory now allow us to study coronal holes in unprecedented detail. Instrumental effects and other factors, however, pose a challenge to automatically detect coronal holes in solar imagery. The science community addresses these challenges with different detection schemes. Until now, little attention has been paid to assessing the disagreement between these schemes. In this COSPAR ISWAT initiative, we present a comparison of nine automated detection schemes widely applied in solar and space science. We study, specifically, a prevailing coronal hole observed by the Atmospheric Imaging Assembly instrument on 2018 May 30. Our results indicate that the choice of detection scheme has a significant effect on the location of the coronal hole boundary. Physical properties in coronal holes such as the area, mean intensity, and mean magnetic field strength vary by a factor of up to 4.5 between the maximum and minimum values. We conclude that our findings are relevant for coronal hole research from the past decade, and are therefore of interest to the solar and space research community.

Keywords: solar physics; solar coronal holes; solar magnetic flux emergence; solar wind; solar extreme ultraviolet emission; solar magnetic fields; space weather
Mock Observations: Formation and Evolution of Diffuse Light in Galaxy Groups and Clusters in the IllustrisTNG Simulations

In this paper, by analyzing mock images from the IllustrisTNG100-1 simulation, we examine the properties of diffuse light and compare them to those of central and satellite galaxies. Our findings suggest that the majority of the diffuse light originates from satellites. This claim is supported by the similarity between the age and metallicity distributions of the diffuse light and those of the satellites. Notably, the color distribution of the diffuse light gradually evolves to resemble that of the centrals at lower redshifts, suggesting a coevolution or passive process. The radial profiles of the diffuse light reveal distinct trends, with the inner regions displaying a relatively flat distribution and the outer regions showing a descending pattern. This finding suggests that the formation of the diffuse light is influenced by both major mergers and stellar tidal stripping. Moreover, strong correlations are found between the stellar mass of the diffuse light and the overall stellar mass of the satellites, as well as between the stellar mass of the diffuse light and the number of satellites within groups or clusters. These relationships can be described by power-law and logarithmic functions. Overall, the diffuse light components predominantly originate from satellites with intermediate ages and metallicities. These satellites typically fall within the stellar mass range $8\lt {{\rm{log}}}_{10}({M}_{\star }/{M}_{\odot })\lt 10$ and the color range -1 < [g - r]0.1 < 0. As the redshift decreases, the growth of the diffuse light is primarily influenced by the redder satellites, while the most massive and reddest satellites have minimal roles in its growth.

Keywords: galaxy clusters; intracluster medium; galaxy evolution; hydrodynamical simulations
Building the First Galaxies—Chapter 2. Starbursts Dominate the Star Formation Histories of 6 < z < 12 Galaxies

We use SEDz*—a code designed to chart the star formation histories (SFHs) of 6 < z < 12 galaxies—to analyze the spectral energy distributions (SEDs) of 894 galaxies with deep JWST/NIRCam imaging by JADES in the GOODS-S field. We show how SEDz* matches observed SEDs using stellar-population templates, graphing the contribution of each epoch by epoch to confirm the robustness of the technique. Very good SED fits for most SFHs demonstrate the compatibility of the templates with stars in the first galaxies—as expected, because their light is primarily from main-sequence A stars, free of post-main-sequence complexity, and insensitive to heavy-element compositions. We confirm earlier results from Dressler et al. (1) There are four types of SFHs: SFH1, burst; SFH2, stochastic; SFH3, "contiguous" (three epochs), and SFH4, "continuous" (four to six epochs). (2) Starbursts—both single and multiple—are predominant (∼70%) in this critical period of cosmic history, although longer SFHs (0.5–1.0 Gyr) contribute one-third of the accumulated stellar mass. These 894 SFHs contribute 1011.14, 1011.09, 1011.00, and 1010.60 M ⊙ for SFH1–4, respectively, adding up to ∼4 × 1011 M ⊙ by z = 6 for this field. We suggest that the absence of rising SFHs could be explained as an intense dust-enshrouded phase of star formation lasting tens of Myr that preceded each of the SFHs we measure. We find no strong dependencies of SFH type with the large-scale environment; however, the discovery of a compact group of 30 galaxies, 11 of which had first star formation at z = 11–12, suggests that long SFHs could dominate in rare, dense environments.

Keywords: early universe
PSR J0030+0451, GW170817, and the Nuclear Data: Joint Constraints on Equation of State and Bulk Properties of Neutron Stars

Very recently the NICER collaboration published the first-ever accurate measurement of mass and radius together for PSR J0030+0451, a nearby isolated quickly rotating neutron star (NS). In this work we set the joint constraints on the equation of state (EoS) and some bulk properties of NSs with the data of PSR J0030+0451, GW170817, and some nuclear experiments. The piecewise polytropic expansion method and the spectral decomposition method have been adopted to parameterize the EoS. The resulting constraints are consistent with each other. Assuming the maximal gravitational mass of nonrotating NS MTOV lies between 2.04M⊙ and 2.4M⊙, with the piecewise method the pressure at twice nuclear saturation density is measured to be 3.19-1.35+2.63 × 1034 dyn cm-2 at the 90% level. For an NS with canonical mass of 1.4M⊙, we have the moment of inertia I1.4= 1.43-0.13+0.30× 1038 kg \cdot m2, tidal deformability Λ1.4 = 370-130+360, radius R1.4 = 12.1-0.8+1.2km, and binding energy BE1.4= 0.16-0.02+0.01 M⊙ at the 90% level, which are improved in comparison to the constraints with the sole data of GW170817. These conclusions are drawn for the mass/radius measurements of PSR J0030+0451 by Riley et al. For the measurements of Miller et al., the results are rather similar.

Keywords: gravitational waves; neutron stars; neutron star cores
Discovery of a Uniquely Cool and Compact Source at 28 pc from the Sun

We present the discovery of what appears to be both a uniquely cool and old white dwarf (WD) within 30 pc of the Sun. DES J214756.46-403529.3 is detected in four separate surveys, 50° away from the Galactic Plane. The combination of its very low luminosity and spectral energy distribution suggests an object unlike any other astrophysical body currently known. Among 8000 of the nearest single objects in the immediate solar neighborhood, it appears completely isolated in multiple color-magnitude diagrams. The data seem compatible with an extremely old and cool WD with a helium dominated atmosphere and a mass around 0.7-0.8 M⊙ but spectroscopic follow-up is required to confirm its nature.

Keywords: white dwarf stars; fundamental parameters of stars
Fitting the Light Curve of 1I/'Oumuamua with a Nonprincipal Axis Rotational Model and Outgassing Torques

In this paper, we investigate the nonprincipal axis (NPA) rotational state of 1I/'Oumuamua-the first interstellar object discovered traversing the inner solar system-from its photometric light curve. Building upon Mashchenko, we develop a model which incorporates NPA rotation and Sun-induced, time-varying outgassing torques to generate synthetic light curves of the object. The model neglects tidal forces, which are negligible compared to outgassing torques over the distances at which 'Oumuamua was observed. We implement an optimization scheme that incorporates the NPA rotation model to calculate the initial rotation state of the object. We find that an NPA rotation state with an average period of <P> ≃ 7.34 hr best reproduces the photometric data. The discrepancy between this period and previous estimates is due to continuous period modulation induced by outgassing torques in the rotational model, as well as different periods being used. The best fit to the 2017 October data does not reproduce the 2017 November data (although the later measurements are too sparse to fit). The light curve is consistent with there being no secular evolution of the angular momentum, which is somewhat in tension with the empirical correlations between nuclear spin-up and cometary outgassing. The complex rotation of 'Oumuamua may be the result of primordial rotation about the smallest principal axis if (i) the object experienced hypervolatile outgassing and (ii) our idealized outgassing model is accurate.

Keywords: interstellar objects; light curves; small solar system bodies
Changing-look Active Galactic Nuclei. I. Tracking the Transition on the Main Sequence of Quasars

This paper is the first in a series of papers that prepare and analyze spectral and other properties for a database of already-discovered changing-look active galactic nuclei (CL AGNs). Here we focus on the spectral fitting and analysis of broad emission lines in a sample of 93 CL AGNs collected from the literature with existing Sloan Digital Sky Survey (SDSS)/Baryon Oscillation Spectroscopic Survey (BOSS)/extended-BOSS spectroscopy where the Hβ emission-line profile does not completely disappear in any epochs. Additionally, we have gathered older/newer spectral epochs from all the available SDSS data releases to make the database more complete. We use PYQSOFIT and perform a homogeneous spectral decomposition of all of our SDSS spectra and tabulate the AGN continuum and emission-line properties per epoch per source, chronologically. This further allows us to categorize the sources in our sample as Turn-On or Turn-Off and subsequently check for repeated occurrences of such phases. We then estimate the black hole mass (M BH) and the Eddington ratio (λ Edd) per epoch per source where the required parameters are available and well estimated. We demonstrate the movement of the source in the M BH–λ Edd plane, allowing us to check for systematic changes in the source's fundamental properties. We then track their transition along the optical plane of the Eigenvector 1 schema and categorize sources that either stay within the same population (A or B) or make an interpopulation movement as a function of spectral epoch. We also test the Balmer decrement (Hα/Hβ) of a subset of our sample of CL AGNs as a function of time and AGN luminosity.

Keywords: quasars; active galactic nuclei; spectroscopy; catalogs; supermassive black holes
The Neupert Effect of Flare Ultraviolet and Soft X-Ray Emissions

We model the Neupert effect that relates flare heating energy with the observed soft X-ray (SXR) emission. The traditional form of the Neupert effect refers to the correlation between the time-integrated hard X-ray or microwave light curve and the SXR light curve. In this paper, we instead use as the proxy for heating energy the ultraviolet (UV) emission at the footpoints of flare loops and modify the model of the Neupert effect by taking into account the discrete nature of flare heating, as well as cooling. In the modified empirical model, spatially resolved UV light curves from the transition region or upper chromosphere are each convolved with a kernel function characterizing the decay of the flare loop emission. Contributions by all loops are summed to compare with the observed total SXR emission. The model has successfully reproduced the observed SXR emission from its rise to decay. To estimate the heating energies in flare loops, we also employ the UV footpoint calorimeter (UFC) method that infers heating rates in flare loops from these UV light curves and models the evolution of flare loops with a zero-dimensional hydrodynamic code. The experiments show that a multitude of impulsive heating events do not well reproduce the observed flare SXR light curve, but a two-phase heating model leads to better agreement with observations. Comparison of the two models of the Neupert effect further allows us to calibrate the UFC method and improve the estimate of heating rates in flare loops continuously formed by magnetic reconnection throughout the flare evolution.

Keywords: solar ultraviolet emission; solar x-ray emission; solar flares; solar magnetic reconnection
Substructures in Protoplanetary Disks Imprinted by Compact Planetary Systems

The substructures observed in protoplanetary disks may be the signposts of embedded planets carving gaps or creating vortices. The inferred masses of these planets often fall in the Jovian regime despite their low abundance compared to lower-mass planets, partly because previous works often assume that a single substructure (a gap or vortex) is caused by a single planet. In this work, we study the possible imprints of compact systems composed of Neptune-like planets (~10-30 M ⊕) and show that long-standing vortices are a prevalent outcome when their interplanetary separation (Δa) falls below ~8 times H p-the average disk's scale height at the planet's locations. In simulations where a single planet is unable to produce long-lived vortices, two-planet systems can preserve them for at least 5000 orbits in two regimes: (i) fully shared density gaps with elongated vortices around the stable Lagrange points L 4 and L 5 for the most compact planet pairs (Δa ≲ 4.6 H p), and (ii) partially shared gaps for more widely spaced planets (Δa ~ 4.6-8 H p) forming vortices in a density ring between the planets through the Rossby wave instability. The latter case can produce vortices with a wide range of aspect ratios down to ~3 and can occur for planets captured into the 3:2 (2:1) mean-motion resonances for disks' aspects ratios of h ≳ 0.033 (h ≳ 0.057). We suggest that their long lifetimes are sustained by the interaction of spiral density waves launched by the neighboring planets. Overall, our results show that the distinguishing imprint of compact systems with Neptune-mass planets are long-lived vortices inside the density gaps, which in turn are shallower than single-planet gaps for a fixed gap width.

Keywords: protoplanetary disks; planetary-disk interactions; hydrodynamical simulations; exoplanet dynamics; exoplanet migration; exoplanet formation
High-resolution Spectroscopy of the GD-1 Stellar Stream Localizes the Perturber near the Orbital Plane of Sagittarius

The 100° long thin stellar stream in the Milky Way halo, GD-1, has an ensemble of features that may be due to dynamical interactions. Using high-resolution MMT/Hectochelle spectroscopy we show that a spur of GD-1-like stars outside of the main stream are kinematically and chemically consistent with the main stream. In the spur, as in the main stream, GD-1 has a low intrinsic radial velocity dispersion, σV_r ≲ 1 km s-1, is metal-poor, [Fe/H] ≈ -2.3, and has little intrinsic spread in the [Fe/H] and [α/Fe] abundances, which point to a common globular cluster progenitor. At a fixed location along the stream, the median radial velocity offset between the spur and the main stream is smaller than 0.5 km s-1, comparable to the measurement uncertainty. A flyby of a massive, compact object can change orbits of stars in a stellar stream and produce features like the spur observed in GD-1. In this scenario, the radial velocity of the GD-1 spur relative to the stream constrains the orbit of the perturber and its current on-sky position to ≈5000 deg2. The family of acceptable perturber orbits overlaps the stellar and dark-matter debris of the Sagittarius dwarf galaxy in present-day position and velocity. This suggests that GD-1 may have been perturbed by a globular cluster or an extremely compact dark-matter subhalo formerly associated with Sagittarius.

Keywords: tidal tails; high resolution spectroscopy; milky way dynamics; milky way dark matter halo
From Pericenter and Back: Full Debris Stream Evolution in Tidal Disruption Events

When a star passes too close to a supermassive black hole, it gets disrupted by strong tidal forces. The stellar debris then evolves into an elongated stream of gas that partly falls back toward the black hole. We present an analytical model describing for the first time the full stream evolution during such a tidal disruption event (TDE). Our framework consists of dividing the stream into different sections of elliptical geometry, whose properties are independently evolved in their comoving frame under the tidal, pressure, and self-gravity forces. Through an explicit treatment of the tidal force and the inclusion of the gas angular momentum, we can accurately follow the stream evolution near pericenter. Our model evolves the longitudinal stream stretching and both transverse widths simultaneously. For the latter, we identify two regimes depending on whether the dynamics is entirely dominated by the tidal force (ballistic regime) or additionally influenced by pressure and self-gravity (hydrostatic regime). We find that the stream undergoes transverse collapses both shortly after the stellar disruption and upon its return near the black hole, at specific locations determined by the regime of evolution considered. The stream evolution predicted by our model can be used to determine the subsequent interactions experienced by this gas that are at the origin of most of the electromagnetic emission from TDEs. Our results suggest that the accretion disk may be fed at a rate that differs from the standard fallback rate, which would provide novel observational signatures dependent on black hole spin.

Keywords: black hole physics; hydrodynamics; galaxy nuclei
Sulfur Dioxide and Other Molecular Species in the Atmosphere of the Sub-Neptune GJ 3470 b

We report observations of the atmospheric transmission spectrum of the sub-Neptune exoplanet GJ 3470 b taken using the Near-Infrared Camera on JWST. Combined with two archival Hubble Space Telescope/Wide-Field Camera 3 transit observations and 15 archival Spitzer transit observations, we detect water, methane, sulfur dioxide, and carbon dioxide in the atmosphere of GJ 3470 b, each with a significance of >3σ. GJ 3470 b is the lowest-mass—and coldest—exoplanet known to show a substantial sulfur dioxide feature in its spectrum, at M p = 11.2 M ⊕ and T eq = 600 K. This indicates that disequilibrium photochemistry drives sulfur dioxide production in exoplanet atmospheres over a wider range of masses and temperatures than has been reported or expected. The water, carbon dioxide, and sulfur dioxide abundances we measure indicate an atmospheric metallicity of approximately 100× solar. We see further evidence for disequilibrium chemistry in our inferred methane abundance, which is significantly lower than expected from equilibrium models consistent with our measured water and carbon dioxide abundances.

Keywords: exoplanet atmospheres; exoplanet atmospheric composition; exoplanet formation
HAT-P-68b: A Transiting Hot Jupiter around a K5 Dwarf Star

We report the discovery by the ground-based Hungarian-made Automated Telescope Network (HATNet) survey of the transiting exoplanet HAT-P-68b, which has a mass of 0.724 ± 0.043 MJ, and radius of 1.072 ± 0.012 RJ. The planet is in a circular P = 2.2984 day orbit around a moderately bright V = 13.937 ± 0.030 magnitude K-dwarf star of mass ${0.673}_{-0.014}^{+0.020}$ M⊙, and radius 0.6726 ± 0.0069 R⊙. The planetary nature of this system is confirmed through follow-up transit photometry obtained with the Fred L. Whipple Observatory (FLWO) 1.2 m telescope, high-precision radial velocities measured using Keck I/High Resolution Echelle Spectrometer (HIRES), FLWO 1.5 m/Tillinghast Reflector Echelle Spectrograph (TRES), and Observatoire de Haute-Provence (OHP) 1.9 m/Sophie, and high-spatial-resolution speckle imaging from WIYN 3.5 m/DSSI. HAT-P-68 is at an ecliptic latitude of +3° and outside the field of view of both the NASA Transiting Exoplanet Survey Satellite primary mission and the K2 mission. The large transit depth of 0.036 mag (r band) makes HAT-P-68b a promising target for atmospheric characterization via transmission spectroscopy. * Based on observations obtained with the Hungarian-made Automated Telescope Network. Based in part on observations made with the Keck I telescope at Maunakea Observatory, Hawaii (Keck time awarded through NASA programs N133Hr and N169Hr). Based in part on observations obtained with the Tillinghast Reflector 1.5 m telescope and the 1.2 m telescope, both operated by the Smithsonian Astrophysical Observatory at the Fred Lawrence Whipple Observatory in Arizona. Based on radial velocities obtained with the Sophie spectrograph mounted on the 1.93 m telescope at Observatoire de Haute-Provence.

Keywords: exoplanet detection methods; exoplanets; transit photometry; exoplanet systems; extrasolar gaseous giant planets; hot jupiters; high resolution spectroscopy; spectroscopy
Solar Modulation of Galactic Cosmic-Ray Protons Based on a Modified Force-field Approach

In this work, a modified force-field approach is established to investigate the long-term solar modulation of galactic cosmic-ray (GCR) protons. In this approach, the solar modulation potential φ is assumed to be energy dependent. As φ also depends on the local interstellar spectrum (LIS), a new proton LIS model is first presented based on data from Voyager 1 and 2, PAMELA, and AMS-02. Then, a double power-law expression is proposed to model φ as a function of proton energy. By fitting to the selected GCR measurements, the solar cycle variation characteristics of parameters in the expression of φ are obtained, and these parameters are reconstructed using the sunspot number, the heliospheric current sheet tilt angle, and the polarity of heliospheric magnetic field. Finally, a new analytical predictive model for GCR protons is established. It is shown that the 11 and 22 yr cyclic variations of GCRs are reproduced, and the computed proton intensities are in good agreement with GCR measurements at various energies since 1954.

Keywords: galactic cosmic rays; solar activity; heliosphere
Localization of Compact Binary Sources with Second-generation Gravitational-wave Interferometer Networks

GW170817 began gravitational-wave multimessenger astronomy. However, GW170817 will not be representative of detections in the coming years because typical gravitational-wave sources will be closer the detection horizon, have larger localization regions, and (when present) will have correspondingly weaker electromagnetic emission. In its design state, the gravitational-wave detector network in the mid-2020s will consist of up to five similar-sensitivity second-generation interferometers. The instantaneous sky-coverage by the full network is nearly isotropic, in contrast to the configuration during the first three observing runs. Along with the coverage of the sky, there are also commensurate increases in the average horizon for a given binary mass. We present a realistic set of localizations for binary neutron stars and neutron star-black hole binaries, incorporating intra-network duty cycles and selection effects on the astrophysical distributions. Based on the assumption of an 80% duty cycle, and that two instruments observe a signal above the detection threshold, we anticipate a median of 28 sq. deg. for binary neutron stars, and 50-120 sq. deg. for neutron star-black hole (depending on the population assumed). These distributions have a wide spread, and the best localizations, even for networks with fewer instruments, will have localizations of 1-10 sq. deg. range. The full five instrument network reduces localization regions to a few tens of degrees at worst.

Keywords: gravitational wave astronomy; gravitational wave detectors; gravitational wave sources; gravitational waves