adsabs/SciX_UAT_keywords huggingface dataset:
Brightness Temperature Constraints on Coherent Processes in Magnetospheres of Neutron Stars

We discuss constraints that the observed brightness temperatures impose on coherent processes in pulsars and fast radio bursts, and in particular on the hypothesis of coherent curvature emission by bunches. We estimate the peak brightness temperature that a bunch of charge Ze can produce via synchrotron and/or curvature emission as kBT ~ (Ze)2/λ, where λ is the typical emitted wavelength. We demonstrate that the bunch's electrostatic energy required to produce observed brightness temperature is prohibitively high, of the order of the total bulk energy. We compare corresponding requirements for the free-electron laser mechanism and find that in that case the constraints are more easily satisfied.

Keywords: pulsars; radio transient sources; radio bursts
orbitize!: A Comprehensive Orbit-fitting Software Package for the High-contrast Imaging Community

orbitize! is an open-source, object-oriented software package for fitting the orbits of directly imaged objects. It packages the Orbits for the Impatient (OFTI) algorithm and a parallel-tempered Markov Chain Monte Carlo (MCMC) algorithm into a consistent and intuitive Python API. orbitize! makes it easy to run standard astrometric orbit fits; in less than 10 lines of code, users can read in data, perform one fit using OFTI and another using MCMC, and make two publication-ready figures. Extensive pedagogical tutorials, intended to be navigable by both orbit-fitting novices and seasoned experts, are available on our documentation page. We have designed the orbitize! API to be flexible and easy to use/modify for unique cases. orbitize! was designed by members of the exoplanet imaging community to be a central repository for algorithms, techniques, and know-how developed by this community. We intend for it to continue to expand and change as the field progresses and new techniques are developed, and call for community involvement in this process. Complete and up-to-date documentation is available at orbitize.info, and the source code is available at github.com/sblunt/orbitize.

Keywords: open source software; orbit determination
A Stochastic Approach to Reconstruct Gamma-Ray-burst Light Curves

Gamma-ray bursts (GRBs), as they are observed at high redshift (z = 9.4), are vital to cosmological studies and investigating Population III stars. To tackle these studies, we need correlations among relevant GRB variables with the requirement of small uncertainties on their variables. Thus, we must have good coverage of GRB light curves (LCs). However, gaps in the LC hinder the precise determination of GRB properties and are often unavoidable. Therefore, extensive categorization of GRB LCs remains a hurdle. We address LC gaps using a stochastic reconstruction, wherein we fit two preexisting models (the Willingale model; W07; and a broken power law; BPL) to the observed LC, then use the distribution of flux residuals from the original data to generate data to fill in the temporal gaps. We also demonstrate a model-independent LC reconstruction via Gaussian processes. At 10% noise, the uncertainty of the end time of the plateau, its correspondent flux, and the temporal decay index after the plateau decreases by 33.3%, 35.03%, and 43.32% on average for the W07, and by 33.3%, 30.78%, 43.9% for the BPL, respectively. The uncertainty of the slope of the plateau decreases by 14.76% in the BPL. After using the Gaussian process technique, we see similar trends of a decrease in uncertainty for all model parameters for both the W07 and BPL models. These improvements are essential for the application of GRBs as standard candles in cosmology, for the investigation of theoretical models, and for inferring the redshift of GRBs with future machine-learning analyses.

Keywords: gamma-ray bursts; gamma-rays; gamma-ray astronomy
Separate Silicate and Carbonaceous Solids Formed from Mixed Atomic and Molecular Species Diffusing in Neon Ice

The formation and growth of refractory matter on pre-existing interstellar dust grain surfaces was studied experimentally by annealing neon-ice matrices in which potential precursors of silicate grains (Mg and Fe atoms, SiO and SiO2 molecules) and of solid carbon (Cn molecules, n = 2-10) were initially isolated. Other molecules, mainly O3, CO, CO2, C3O, and H2O, were embedded at the same time in the matrices. The annealing procedure caused the cold dopants to diffuse and interact in the neon ice. Monitoring the procedure in situ with infrared spectroscopy revealed the disappearance of the silicon oxide and carbon molecules at temperatures lower than 13 K, and the rise of the Si-O stretching band of silicates. Ex situ electron microscopy confirmed the formation of silicate grains and showed that their structure was amorphous. It also showed that amorphous carbon matter was formed simultaneously next to the silicate grains, the two materials being chemically separated. The results of the experiments support the hypothesis that grains of complex silicates and of carbonaceous materials are reformed in the cold interstellar medium, as suggested by astronomical observations and evolution models of cosmic dust masses. Moreover, they show that the potential precursors of one material do not combine with those of the other at cryogenic temperatures, providing us with a clue as to the separation of silicates and carbon in interstellar grains.

Keywords: laboratory astrophysics; interstellar dust processes; silicate grains; carbonaceous grains; interstellar dust
Determination of Size, Albedo, and Thermal Inertia of 10 Vesta Family Asteroids with WISE/NEOWISE Observations

In this work, we investigate the size, thermal inertia, surface roughness, and geometric albedo of 10 Vesta family asteroids using the Advanced Thermophysical Model, based on the thermal-infrared data acquired by mainly NASA's Wide-field Infrared Survey Explorer. Here, we show that the average thermal inertia and geometric albedo of the investigated Vesta family members are 42 J m-2 s-1/2 K-1 and 0.314, respectively, where the derived effective diameters are less than 10 km. Moreover, the family members have a relatively low roughness fraction on their surfaces. The similarity in thermal inertia and geometric albedo among the V-type Vesta family members may reveal their close connection in origin and evolution. As the fragments of the cratering event of Vesta, the family members may have undergone a similar evolutionary process, thereby leading to very close thermal properties. Finally, we estimate their regolith grain sizes with different volume filling factors.

Keywords: main belt asteroids
A KELT-TESS Eclipsing Binary in a Young Triple System Associated with the Local "Stellar String" Theia 301

HD 54236 is a nearby, wide common-proper-motion visual pair that has been previously identified as likely being very young by virtue of strong X-ray emission and lithium absorption. Here, we report the discovery that the brighter member of the wide pair, HD 54236A, is itself an eclipsing binary (EB), comprising two near-equal solar-mass stars on a 2.4 days orbit. It represents a potentially valuable opportunity to expand the number of benchmark-grade EBs at young stellar ages. Using new observations of Ca II H and K emission and lithium absorption in the wide K-dwarf companion, HD 54236B, we obtain a robust age estimate of 225 ± 50 Myr for the system. This age estimate and Gaia proper motions show HD 54236 is associated with Theia 301, a newly discovered local "stellar string," which itself may be related to the AB Dor moving group through shared stellar members. Applying this age estimate to AB Dor itself alleviates reported tension between observation and theory that arises for the luminosity of AB Dor C when younger age estimates are used.

Keywords: eclipsing binary stars; fundamental parameters of stars; stellar associations; low mass stars
Serendipitous Archival Observations of a New Ultradistant Comet C/2019 E3 (ATLAS)

We identified a new ultradistant comet C/2019 E3 (ATLAS) exhibiting preperihelion cometary activity at heliocentric distances ≳20 au, making it the fourth member of this population after C/2010 U3 (Boattini), C/2014 UN271 (Bernardinelli–Bernstein), and C/2017 K2 (PANSTARRS). From serendipitous archival data, we conducted analyses of the comet, finding that the activity was consistent with steady-state behavior, suggestive of sublimation of supervolatiles; that the cross section of dust increased gradually on the inbound leg of the orbit, varying with heliocentric distances as ${r}_{{\rm{H}}}^{-1.5\pm 0.4}$ ; and that the dust was produced at a rate of ≳102 kg s‑1 within the observed timespan. Our modeling of the largely symmetric morphology of the comet suggests that the dust environment was likely dominated by mm-scale dust grains ejected at speeds ≲0.4 m s‑1 from the sunlit hemisphere of the nucleus. Assuming a typical geometric albedo of 0.05 and adopting several simplistic thermophysical models, we estimated the nucleus to be at least ∼3 km across. We also measured the color of the comet to be consistent with other long-period comets, except being slightly bluer in g ‑ r. With our astrometric measurements, we determined an improved orbit of the comet, based upon which we derived that the comet is dynamically new and that its perihelion distance will further shrink due to the Galactic tide. We conclude the paper by comparing the known characteristics of the known ultradistant comets.

Keywords: long period comets; comets; oort cloud objects
The Evaporating Primordial Black Hole Fraction in Cool-core Galaxy Clusters

Recent studies of gamma-ray, cosmic-ray, and radio data put stringent constraints on the fraction of primordial black holes (PBHs) in our universe. In this article, we propose a new indirect method in using the X-ray luminosity data of cool-core clusters to constrain the evaporating PBH fraction for the monochromatic, log-normal and power-law mass distributions. The present results show that the amount of evaporating PBHs only constitutes a minor component of dark matter for a large parameter space. The constraints are consistent with and close to that obtained from other cosmic-ray and multiwavelength observations.

Keywords: primordial black holes; dark matter
CORINOS. I. JWST/MIRI Spectroscopy and Imaging of a Class 0 Protostar IRAS 15398-3359

The origin of complex organic molecules (COMs) in young Class 0 protostars has been one of the major questions in astrochemistry and star formation. While COMs are thought to form on icy dust grains via gas-grain chemistry, observational constraints on their formation pathways have been limited to gas-phase detection. Sensitive mid-infrared spectroscopy with JWST enables unprecedented investigation of COM formation by measuring their ice absorption features. Mid-infrared emission from disks and outflows provide complementary constraints on the protostellar systems. We present an overview of JWST/Mid-Infrared Instrument (MIRI) Medium Resolution Spectroscopy (MRS) and imaging of a young Class 0 protostar, IRAS 15398-3359, and identify several major solid-state absorption features in the 4.9-28 μm wavelength range. These can be attributed to common ice species, such as H2O, CH3OH, NH3, and CH4, and may have contributions from more complex organic species, such as C2H5OH and CH3CHO. In addition to ice features, the MRS spectra show many weaker emission lines at 6-8 μm, which are due to warm CO gas and water vapor, possibly from a young embedded disk previously unseen. Finally, we detect emission lines from [Fe II], [Ne II], [S I], and H2, tracing a bipolar jet and outflow cavities. MIRI imaging serendipitously covers the southwestern (blueshifted) outflow lobe of IRAS 15398-3359, showing four shell-like structures similar to the outflows traced by molecular emission at submillimeter wavelengths. This overview analysis highlights the vast potential of JWST/MIRI observations and previews scientific discoveries in the coming years.

Keywords: astrochemistry; star formation; protostars; stellar winds; stellar jets; complex organic molecules
On the Evolution of the Anisotropic Scaling of Magnetohydrodynamic Turbulence in the Inner Heliosphere

We analyze a merged Parker Solar Probe (PSP) and Solar Orbiter (SO) data set covering heliocentric distances 13 R ⊙ ≲ R ≲ 220 R ⊙ to investigate the radial evolution of power and spectral index anisotropy in the wavevector space of solar wind turbulence. Our results show that anisotropic signatures of turbulence display a distinct radial evolution when fast, V sw ≥ 400 km s-1, and slow, V sw ≤ 400 km s-1, wind streams are considered. The anisotropic properties of slow wind in Earth orbit are consistent with a "critically balanced" cascade, but both spectral index anisotropy and power anisotropy diminish with decreasing heliographic distance. Fast streams are observed to roughly retain their near-Sun anisotropic properties, with the observed spectral index and power anisotropies being more consistent with a "dynamically aligned" type of cascade, though the lack of extended fast wind intervals makes it difficult to accurately measure the anisotropic scaling. A high-resolution analysis during the first perihelion of PSP confirms the presence of two subranges within the inertial range, which may be associated with the transition from weak to strong turbulence. The transition occurs at κ d i ≈ 6 × 10-2 and signifies a shift from -5/3 to -2 and from -3/2 to -1.57 scaling in parallel and perpendicular spectra, respectively. Our results provide strong observational constraints for anisotropic theories of MHD turbulence in the solar wind.

Keywords: interplanetary turbulence; solar wind; space plasmas; magnetohydrodynamics; plasma astrophysics
Photometric Observations of KEPLER Mission's Eclipsing Binary EPIC 201458798 (V0337Leo)

Two follow up observing sessions of Kepler's Eclipsing Binary star system EPIC 201458798 (from the K2 mission) were conducted in the Spring of 2018 and 2019 utilizing the 0.4 m subnet of the Los Cumbres Observatory Global Telescope network. The total duration of observations for each session (~77 days) was comparable with the duration of observations by the Kepler telescope ~80 days. 900-1000 images were obtained during each session with an integrating time around 1 minute, resulting in about 800 mag measurements per session. In contrast, the Kepler telescope provided almost continuous measurements of this star with an integration time per image of about 30 minutes, resulting in about 3250 photometric points. In contrast to the Kepler telescope measurements, which were conducted with one very broad filter, the observations in this study used four filters: B, V, ip, and rp. This data was processed and the period, time of minimum, and depth of the eclipses was determined. The results were compared with the data obtained by the Kepler telescope and other historical records.

Keywords: eclipsing binary stars
Spectral Anisotropy in 2D plus Slab Magnetohydrodynamic Turbulence in the Solar Wind and Upper Corona

The 2D + slab superposition model of solar wind turbulence has its theoretical foundations in nearly incompressible magnetohydrodynamics (NI MHD) in the plasma beta ∼1 or ≪1 regimes. Solar wind turbulence measurements show that turbulence in the inertial range is anisotropic, for which the superposition model offers a plausible explanation. We provide a detailed theoretical analysis of the spectral characteristics of the Elsässer variables in the 2D + NI/slab model. We find that (1) the majority 2D component has a power spectrum ${G}^{\infty }({k}_{\perp })\sim {k}_{\perp }^{-5/3}$ in perpendicular wavenumber k⊥; (2) the strongly imbalanced minority NI/slab turbulence has power spectra ${G}^{* }({k}_{\perp })\sim {k}_{\perp }^{-5/3}$ and ${G}^{* }({k}_{z})\sim {k}_{z}^{-5/3}$ , where kz is aligned with the mean magnetic field; (3) NI/slab turbulence can exhibit a double-power-law spectrum, with the steeper part being G*(k) ∼ k-5/3 and corresponding to strong turbulence and the flatter spectrum satisfying G*(k) ∼ k-3/2 and corresponding to weak turbulence; (4) there is a critical balance regime for NI/slab turbulence that satisfies ${G}^{* }({k}_{z})\sim {k}_{z}^{-2}$ and ${G}^{* }({k}_{\perp })\sim {k}_{\perp }^{-5/3}$ ; and (5) the forward and backward Elsässer power spectra can have different spectral forms provided that the triple-correlation times for each are different. We use the spectral analysis to compute the total power spectra in frequency parallel to the solar wind flow for the superposition model, showing that strongly imbalanced turbulence yields an f-5/3 spectrum for all angles between the mean flow and magnetic field, and that double power laws are possible when the nonlinear and Alfvén timescales are both finite.

Keywords: interplanetary turbulence
Efficient Detection of Emission-line Galaxies in the Cl0016+1609 and MACSJ1621.4+3810 Supercluster Filaments Using SITELLE

We observe a system of filaments and clusters around Cl0016+1609 and MACSJ1621.4+3810 using the SITELLE Fourier transform spectrograph at the Canada-France-Hawaii Telescope. For Cl0016+1609 (z = 0.546), the observations span an 11.8 Mpc × 4.3 Mpc region along an eastern filament that covers the main cluster core, as well as two 4.3 Mpc × 4.3 Mpc regions that each cover southern subclumps. For MACSJ1621.4+3810 (z = 0.465), 3.9 Mpc × 3.9 Mpc around the main cluster core is covered. We present the frequency and location of the emission-line galaxies and their emission-line images, and calculate the star formation rates, specific star formation rates, and merger statistics. In Cl0016+1609, we find 13 [O II] 3727 Å emitting galaxies with star formation rates between 0.2 and 14.0 M⊙ yr-1. Of these, ${91}_{-10}^{+3}$ % are found in regions with moderate local galaxy density, avoiding the dense cluster cores. These galaxies follow the main filament of the superstructure and are mostly blue and disky, with several showing close companions and merging morphologies. In MACSJ1621.4+3810, we find 10 emission-line sources. All are blue ( ${100}_{-15}^{+0}$ %), with ${40}_{-12}^{+16}$ % classified as disky and ${60}_{-16}^{+12}$ % as merging systems. Eight avoid the cluster core ( ${80}_{-17}^{+7}$ %), but two ( ${20}_{-7}^{+17}$ %) are found near high-density regions, including the brightest cluster galaxy (BCG). These observations push the spectroscopic study of galaxies in filaments beyond z ∼ 0.3 to z ∼ 0.5. Their efficient confirmation is paramount to their usefulness as more galaxy surveys come online. * Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated from the summit of Maunakea by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. The observations at the Canada-France-Hawaii Telescope were performed with care and respect from the summit of Maunakea which is a significant cultural and historic site. The corresponding proposals were: 17BF001, 18BF001 and 19AF001.

Keywords: galaxy colors; emission line galaxies; galaxy masses; superclusters; galaxy clusters; intergalactic filaments
Multi-wavelength Observations of AT2019wey: a New Candidate Black Hole Low-mass X-ray Binary

AT2019wey (SRGA J043520.9+552226, SRGE J043523.3+552234) is a transient first reported by the ATLAS optical survey in 2019 December. It rose to prominence upon detection, three months later, by the Spektrum-Roentgen-Gamma (SRG) mission in its first all-sky survey. X-ray observations reported in Yao et al. suggest that AT2019wey is a Galactic low-mass X-ray binary (LMXB) with a black hole (BH) or neutron star (NS) accretor. Here we present ultraviolet, optical, near-infrared, and radio observations of this object. We show that the companion is a short-period (P ≲ 16 hr) low-mass (<1 M⊙) star. We consider AT2019wey to be a candidate BH system since its locations on the Lradio-LX and Lopt-LX diagrams are closer to BH binaries than NS binaries. We demonstrate that from 2020 June to August, despite the more than 10 times brightening at radio and X-ray wavelengths, the optical luminosity of AT2019wey only increased by 1.3-1.4 times. We interpret the UV/optical emission before the brightening as thermal emission from a truncated disk in a hot accretion flow and the UV/optical emission after the brightening as reprocessing of the X-ray emission in the outer accretion disk. AT2019wey demonstrates that combining current wide-field optical surveys and SRG provides a way to discover the emerging population of short-period BH LMXB systems with faint X-ray outbursts.

Keywords: low-mass x-ray binary stars; accretion; astrophysical black holes; sky surveys
Identifying Exoplanets with Deep Learning. V. Improved Light-curve Classification for TESS Full-frame Image Observations

The TESS mission produces a large amount of time series data, only a small fraction of which contain detectable exoplanetary transit signals. Deep-learning techniques such as neural networks have proved effective at differentiating promising astrophysical eclipsing candidates from other phenomena such as stellar variability and systematic instrumental effects in an efficient, unbiased, and sustainable manner. This paper presents a high-quality data set containing light curves from the Primary Mission and 1st Extended Mission full-frame images and periodic signals detected via box least-squares. The data set was curated using a thorough manual review process then used to train a neural network called Astronet-Triage-v2. On our test set, for transiting/eclipsing events, we achieve a 99.6% recall (true positives over all data with positive labels) at a precision of 75.7% (true positives over all predicted positives). Since 90% of our training data is from the Primary Mission, we also test our ability to generalize on held-out 1st Extended Mission data. Here, we find an area under the precision-recall curve of 0.965, a 4% improvement over Astronet-Triage. On the TESS object of interest (TOI) Catalog through 2022 April, a shortlist of planets and planet candidates, Astronet-Triage-v2 is able to recover 3577 out of 4140 TOIs, while Astronet-Triage only recovers 3349 targets at an equal level of precision. In other words, upgrading to Astronet-Triage-v2 helps save at least 200 planet candidates from being lost. The new model is currently used for planet candidate triage in the Quick-Look Pipeline.

Keywords: neural networks; transit photometry; exoplanet detection methods; exoplanet catalogs