adsabs/SciX_UAT_keywords huggingface dataset:
A Contact Binary Misclassified as an Ellipsoidal Variable: Complications for Detached Black Hole Searches

Identifying sources exhibiting ellipsoidal variability in large photometric surveys is becoming a promising method to search for candidate detached black holes (BHs) in binaries. This technique aims to exploit the orbital-phase-dependent modulation in optical photometry caused by the BH distorting the shape of the luminous star to constrain the mass ratio of the binary. Without understanding if, or how much, contamination is present in the candidate BH samples produced by this new technique it is hard to leverage them for BH discovery. Here, we follow up one of the best candidates identified from Gaia Data Release 3, Gaia DR3 4042390512917208960, with a radial velocity (RV) campaign. Combined photometric and RV modeling, along with spectral disentangling, suggests that the true mass ratio (the mass of the unseen object divided by the mass of the luminous star) is an order of magnitude smaller than that inferred assuming the modulations arise from ellipsoidal variability. We therefore infer that this system is likely a contact binary, or on the boundary of both stars nearly filling their Roche lobes; however, further observations are required to confidently detect the secondary. We find that the well-known problem of discriminating between ellipsoidal and contact binary light curves results in a larger contamination from contact binaries than previously suggested. Until ellipsoidal variables can be reliably distinguished from contact binaries, samples of BH candidates selected based on ellipsoidal variability are likely to be highly contaminated by contact binaries or similar systems.

Keywords: stellar mass black holes; ellipsoidal variable stars; close binary stars; contact binary stars; spectroscopy
Outward Migration of Super-Jupiters

Recent simulations show that giant planets of about 1 MJ migrate inward at a rate that differs from the type II prediction. Here we show that at higher masses, planets migrate outward. Our result differs from previous ones because of our longer simulation times, lower viscosity, and boundary conditions that allow the disk to reach a viscous steady state. We show that, for planets on circular orbits, the transition from inward to outward migration coincides with the known transition from circular to eccentric disks that occurs for planets more massive than a few Jupiters. In an eccentric disk, the torque on the outer disk weakens due to two effects: the planet launches weaker waves, and those waves travel further before damping. As a result, the torque on the inner disk dominates, and the planet pushes itself outward. Our results suggest that the many super-Jupiters observed by direct imaging at large distances from the star may have gotten there by outward migration.

Keywords: protoplanetary disks; planetary migration; planet formation
Particle Acceleration and Their Escape into the Heliosphere in Solar Flares with Open Magnetic Field

Energetic particle populations in the solar corona and in the heliosphere appear to have different characteristics even when produced in the same solar flare. It is not clear what causes this difference: properties of the acceleration region, the large-scale magnetic field configuration in the flare, or particle transport effects, such as scattering. In this study, we use a combination of magnetohydrodynamic and test-particle approaches to investigate magnetic reconnection, particle acceleration, and transport in two solar flares: an M-class flare on 2013 June 19, and an X-class flare on 2011 September 6. We show that in both events, the same regions are responsible for the acceleration of particles remaining in the coronal and being ejected toward the heliosphere. However, the magnetic field structure around the acceleration region acts as a filter, resulting in different characteristics (such as energy spectra) acquired by these two populations. We argue that this effect is an intrinsic property of particle acceleration in the current layers created by the interchange reconnection, and therefore, may be ubiquitous, particularly, in noneruptive solar flares with substantial particle emission into the heliosphere.

Keywords: solar flares; solar energetic particles; computational methods
The Behavior of HgMn Stars in the Far UV-3: 53 Tau and HD 35548

The analysis of high resolution SWP spectra of the HgMn stars HD 27295 (53 Tau) and HD 33548 obtained through the large aperture recorded by the International Ultraviolet Explorer reveals that the far ultraviolet flux of these two stars remained constant over the various observations with IUE. The TESS lightcurves of 53 Tau show a periodic sine structure with a period estimated to be around 4.43 days whereas that of HD 35548 do not show evidence for periodic variability. The absence of far and mid-UV variability of these two stars precludes the presence of large chemical gradients over their surfaces at the time of the IUE observations.

Keywords: chemically peculiar stars
The Bimodal Absorption System Imaging Campaign (BASIC). I. A Dual Population of Low-metallicity Absorbers at z < 1

The bimodal absorption system imaging campaign (BASIC) aims to characterize the galaxy environments of a sample of 36 H I-selected partial Lyman limit systems (pLLSs) and Lyman limit systems (LLSs) in 23 QSO fields at z ≲ 1. These pLLSs/LLSs provide a unique sample of absorbers with unbiased and well-constrained metallicities, allowing us to explore the origins of metal-rich and low-metallicity circumgalactic medium (CGM) at z < 1. Here we present Keck/KCWI and Very Large Telescope/MUSE observations of 11 of these QSO fields (19 pLLSs) that we combine with Hubble Space Telescope/Advanced Camera for Surveys imaging to identify and characterize the absorber-associated galaxies at 0.16 ≲ z ≲ 0.84. We find 23 unique absorber-associated galaxies, with an average of one associated galaxy per absorber. For seven absorbers, all with <10% solar metallicities, we find no associated galaxies with $\mathrm{log}{M}_{\star }\gtrsim 9.0$ within ρ/R vir and ∣Δv∣/v esc ≤ 1.5 with respect to the absorber. We do not find any strong correlations between the metallicities or H I column densities of the gas and most of the galaxy properties, except for the stellar mass of the galaxies: the low-metallicity ([X/H] ≤ -1.4) systems have a probability of ${0.39}_{-0.15}^{+0.16}$ for having a host galaxy with $\mathrm{log}{M}_{\star }\geqslant 9.0$ within ρ/R vir ≤ 1.5, while the higher metallicity absorbers have a probability of ${0.78}_{-0.13}^{+0.10}$ . This implies metal-enriched pLLSs/LLSs at z < 1 are typically associated with the CGM of galaxies with $\mathrm{log}{M}_{\star }\gt 9.0$ , whereas low-metallicity pLLSs/LLSs are found in more diverse locations, with one population arising in the CGM of galaxies and another more broadly distributed in overdense regions of the universe. Using absorbers not associated with galaxies, we estimate the unweighted geometric mean metallicity of the intergalactic medium to be [X/H] ≲ -2.1 at z < 1, which is lower than previously estimated.

Keywords: circumgalactic medium; galaxy spectroscopy; intergalactic medium; lyman limit systems; metallicity; quasar absorption line spectroscopy
Direct Measurements of Activation Energies for Surface Diffusion of CO and CO2 on Amorphous Solid Water Using In Situ Transmission Electron Microscopy

The importance of the activation energy of surface diffusion (Esd) of adsorbed molecules on amorphous solid water (ASW) has been widely discussed in terms of chemical reactions on ASW at low temperatures. However, in previous work, Esd has not been measured directly but estimated from indirect experiments. It has been assumed in chemical network calculations that Esd is between 0.3 and 0.8 of the desorption energies of a molecule. It remains important to obtain direct measurements of Esd. We performed in situ observations of the deposition process of CO and CO2 on ASW using transmission electron microscopy (TEM) and deduced the Esd of CO and CO2 on ASW to be 350 ± 50 and 1500 ± 100 K, respectively. The value of Esd of CO is approximately 0.3 of the total adsorption energy of CO on ASW, I.e., much smaller than assumed in chemical network calculations, where the corresponding figure is 575 K, assuming approximately 0.5 of the desorption energy. We demonstrated that TEM is very useful not only for the observation of ices but also for the measurement of some physical properties that are relevant in astrochemistry and astrophysics. Using the Esd of CO measured in the present study (350 K), we have updated the chemical network model of Furuya et al., confirming that CO2 could be efficiently formed by the reaction CO + OH → CO2 + H in the initial stages of the evolution of molecular clouds.

Keywords: astrochemistry; reaction rates; experimental techniques; ice formation; theoretical models; laboratory astrophysics; interdisciplinary astronomy; interstellar molecules; dense interstellar clouds
A Spatially Resolved [C II] Survey of 31 z ∼ 7 Massive Galaxies Hosting Luminous Quasars

The [C II] 158 μm emission line and the underlying far-infrared (FIR) dust continuum are important tracers for studying star formation and kinematic properties of early galaxies. We present a survey of the [C II] emission lines and FIR continua of 31 luminous quasars at z > 6.5 using the Atacama Large Millimeter Array (ALMA) and the NOrthern Extended Millimeter Array at sub-arcsec resolution. This survey more than doubles the number of quasars with [C II] and FIR observations at these redshifts and enables statistical studies of quasar host galaxies deep into the epoch of reionization. We detect [C II] emission in 27 quasar hosts with a luminosity range of L [C II] = (0.3–5.5) × 109 L ⊙ and detect the FIR continuum of 28 quasar hosts with a luminosity range of L FIR = (0.5–13.0) × 1012 L ⊙. Both L [C II] and L FIR are correlated (ρ ≃ 0.4) with the quasar bolometric luminosity, albeit with substantial scatter. The quasar hosts detected by ALMA are clearly resolved with a median diameter of ∼5 kpc. About 40% of the quasar host galaxies show a velocity gradient in [C II] emission, while the rest show either dispersion-dominated or disturbed kinematics. Basic estimates of the dynamical masses of the rotation-dominated host galaxies yield M dyn = (0.1–7.5) × 1011 M ⊙. Considering our findings alongside those of literature studies, we found that the ratio between M BH and M dyn is about 10 times higher than that of local M BH–M dyn relation on average but with substantial scatter (the ratio difference ranging from ∼0.6 to 60) and large uncertainties.

Keywords: early universe; galaxies; quasars; supermassive black holes
Additional Calibration of the Ultraviolet Imaging Telescope on Board AstroSat

Results of the initial calibration of the Ultra-Violet Imaging Telescope (UVIT) were reported earlier by Tandon et al. The results reported earlier were based on the ground calibration as well as the first observations in orbit. Some additional data from the ground calibration and data from more in-orbit observations have been used to improve the results. In particular, extensive new data from in-orbit observations have been used to obtain (a) new photometric calibration that includes (i) zero points, (ii) flat fields, and (iii) saturation; (b) sensitivity variations; (c) spectral calibration for the near ultraviolet (NUV; 2000-3000 Å) and far ultraviolet (FUV; 1300-1800 Å) gratings; (d) point-spread function; and (e) astrometric calibration including distortion. Data acquired over the last three years show continued good performance of UVIT with no reduction in sensitivity in both UV channels.

Keywords: ultraviolet astronomy; ultraviolet telescopes; astronomical instrumentation; ultraviolet photometry; spectroscopy
Molecular and Atomic Clouds Associated with the Gamma-Ray Supernova Remnant Puppis A

We have carried out a study of the interstellar medium (ISM) toward the shell-like supernova remnant (SNR) Puppis A using NANTEN CO and ATCA H I data. We synthesized a comprehensive picture of the SNR radiation by combining the ISM data with the gamma-ray and X-ray distributions. The ISM, both atomic and molecular gas, is dense and highly clumpy, and is distributed all around the SNR, but mainly in the northeast. The CO distribution revealed an enhanced line intensity ratio of CO(J = 2-1)/(J = 1-0) transitions as well as CO line broadening, which indicate shock heating/acceleration. The results support the assertion that Puppis A is located at 1.4 kpc, in the Local Arm. The ISM interacting with the SNR has a large mass of ~104 M ⊙, which is dominated by H I, showing good spatial correspondence with the Fermi-LAT gamma-ray image. This favors a hadronic origin of the gamma-rays, while an additional contribution from a leptonic component is not excluded. The distribution of the X-ray ionization timescales within the shell suggests that the shock front ionized various parts of the ISM at epochs ranging over a few to ten thousand years. We therefore suggest that the age of the SNR is around 104 yr as given by the largest ionization timescale. We estimate the total cosmic-ray energy W p to be 1047 erg, which is well placed in the cosmic-ray escaping phase of an age-W p plot including more than ten SNRs.

Keywords: supernova remnants; interstellar medium; cosmic ray sources; gamma-ray sources; x-ray sources
Downstream Depolarization in the Sausage Relic: A 1-4 GHz Very Large Array Study

Radio relics are elongated sources related to shocks driven by galaxy cluster merger events. Although these objects are highly polarized at GHz frequencies (≳20%), high-resolution studies of their polarization properties are still lacking. We present the first high-resolution and high-sensitivity polarimetry study of the merging galaxy cluster CIZA J2242.8+5301 in the 1-4 GHz frequency band. We use the QU-fitting approach to model the Stokes I, Q, and U emission, obtaining best-fit intrinsic polarization fraction (p0), intrinsic polarization angle (χ0), rotation measure (RM), and wavelength-dependent depolarization (σRM) maps of the cluster. Our analysis focuses on the northern relic (RN). For the first time in a radio relic, we observe a decreasing polarization fraction in the downstream region. Our findings are possibly explained by geometrical projections and/or by decreasing of the magnetic field anisotropy toward the cluster center. From the amount of depolarization of the only detected background radio galaxy, we estimate a turbulent magnetic field strength of Bturb ∼ 5.6 μG in the relic. Finally, we observe RM fluctuations of about 30 rad m-2 around the median value of 140.8 rad m-2 at the relic position.

Keywords: galaxy clusters; galactic and extragalactic astronomy; polarimetry; intracluster medium; shocks; plasma astrophysics
High-resolution Extinction Map in the Direction of the Strongly Obscured Bulge Fossil Fragment Liller 1

We used optical images acquired with the Wide Field Camera of the Advanced Camera for Surveys on board the Hubble Space Telescope and near-infrared data from Gemini Multi-conjugate Adaptive Optics System (GeMS)/Gemini South Adaptive Optics Imager (GSAOI) to construct a high-resolution extinction map in the direction of the bulge stellar system Liller 1. In spite of its appearance of a globular cluster, Liller 1 has been recently found to harbor two stellar populations with remarkably different ages, and it is the second complex stellar system with similar properties (after Terzan 5) discovered in the bulge, thus defining a new class of objects: the Bulge Fossil Fragments. Because of its location in the inner bulge of the Milky Way, very close to the Galactic plane, Liller 1 is strongly affected by large and variable extinction. The simultaneous study of both the optical and the near-infrared color-magnitude diagrams revealed that the extinction coefficient RV in the direction of Liller 1 has a much smaller value than commonly assumed for diffuse interstellar medium (RV = 2.5, instead of 3.1), in agreement with previous findings along different light paths to the Galactic bulge. The derived differential reddening map has a spatial resolution ranging from 1″ to 3″ over a field of view of about 90″ × 90″. We found that the absorption clouds show patchy substructures with extinction variations as large as δE(B - V) ~ 0.9 mag. * Based on observations collected with the NASA/ESA HST (Prop. GO 15231), obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555. Based on observations (Prop. GS-2013-Q-23) obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil), and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina). Based on observations gathered with the ESO-VISTA telescope (program ID 179.B-2002).

Keywords: globular star clusters; star clusters; reddening law; extinction; galactic bulge
Binary Fraction Estimation of Main-sequence Stars in 12 Open Clusters: Based on the Homogeneous Data of LAMOST Survey and Gaia DR2

Based on the homogeneous low-resolution spectra data observed by Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and the Gaia Data Release 2 (Gaia DR2) photometric data, we chose 12 open clusters (OCs) to study their fundamental parameters and binary fractions (BFs). For each OC, more than 20 cluster members were observed by LAMOST, and some of them were observed multiple times. We used these data to derive precise metallicities of OCs. Combining the metallicities and the Gaia DR2 photometric data, we used the isochrone fitting method to obtain fundamental parameters of these OCs. By fixing metallicity during the fitting, we avoided the effect of degeneracy between the metallicity and reddening. Based on the fundamental parameters, we utilized the synthetic color-magnitude diagram (CMD) method to derive the BFs of main-sequence (MS) stars, the mass functions (MFs) with correction of binaries, and the companion mass ratio distributions. The BFs of observed MS stars in OCs in this paper vary from 29% to 55%. Extrapolating the synthetic CMD to the hydrogen-burning limit, the BFs vary from 13% to 47%. Combining MFs published by previous literature with our results, we found that MFs with correction of binaries were steeper than those without correction by Δα = 0.6 ± 0.16 in the mass range of m ∈ [1M⊙, 2.67M⊙]. We found that the companion mass ratio distribution in OCs of our sample was flat. We also found a significant positive correlation between the BF and density.

Keywords: open star clusters; binary stars; stellar dynamics; observational astronomy
Rapid Transients Originating from Thermonuclear Explosions in Helium White Dwarf Tidal Disruption Events

We study the emission properties of thermonuclear explosions in a helium white dwarf (WD) tidal disruption event (TDE). We consider a TDE where a 0.2 M⊙ helium WD is disrupted by a 102.5 M⊙ intermediate-mass black hole (IMBH). The helium WD is not only tidally disrupted but is also detonated by the tidal compression and by succeeding shocks. We focus on the emission powered by radioactive nuclei in the unbound TDE ejecta. We perform hydrodynamic simulations coupled with nuclear reactions, post-process detailed nucleosynthesis calculations, and radiative transfer simulations. We thus derive multi-band light curves and spectra. The helium WD TDE shows rapid (Δt1mag ≃ 5-10 days) and relatively faint ( ${L}_{\mathrm{peak}}\simeq {10}^{42}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ ) light curves, because the ejecta mass and 56Ni mass are low (0.12 M⊙ and 0.03 M⊙, respectively). The spectra show strong calcium and Fe-peak features and very weak silicon features, reflecting the peculiar elemental abundance. The key feature is the Doppler shift of the spectral lines up to ≃ ±12,000 km s-1, depending on the viewing angle, due to the bulk motion of the ejecta. Our model matches well with two rapid and faint transients reported in Pursiainen et al. The particular model presented here does not match with observed SNe Iax, calcium-rich transients, or .Ia explosion candidates, either in the spectra or light curves. However, we expect a large variety of observational signatures once a wide range of the WD/black hole masses and orbital parameters are considered. This study contributes to the search for WD TDEs with current and upcoming surveys, and to the identification of IMBHs as disrupters in TDEs.

Keywords: explosive nucleosynthesis; helium burning; nucleosynthesis; radiative transfer simulations; astronomical simulations; white dwarf stars; intermediate-mass black holes; black holes; supernovae; radiative transfer; tidal disruption; hydrodynamical simulations
JWST NIRCam Defocused Imaging: Photometric Stability Performance and How It Can Sense Mirror Tilts

We use JWST NIRCam short-wavelength photometry to capture a transit lightcurve of the exoplanet HAT-P-14 b to assess performance as part of instrument commissioning. The short-wavelength precision is 152 ppm per 27 s integration as measured over the full time series compared to a theoretical limit of 107 ppm, after corrections to spatially correlated 1/f noise. Persistence effects from charge trapping are well fit by an exponential function with short characteristic timescales, settling on the order of 5-15 minutes. The short-wavelength defocused photometry is also uniquely well suited to measure the real-time wave-front error of JWST. Analysis of the images and reconstructed wave-front maps indicates that two different hexagonal primary mirror segments exhibited "tilt events," where they changed orientation rapidly in less than ~1.4 s. In some cases, the magnitude and timing of the flux jumps caused by tilt events can be accurately predicted with a telescope model. These tilt events can be sensed by simultaneous longer-wavelength NIRCam grism spectral images alone in the form of changes to the point-spread function, diagnosed from the full width at half maximum. They can also be sensed with the fine guidance sensor instrument from difference images. Tilt events possibly from sudden releases of stress in the backplane structure behind the mirrors were expected during the commissioning period because they were found in ground-based testing. Tilt events have shown signs of decreasing in frequency but have not disappeared completely. The detectors exhibit some minor (less than 1%) deviations from linear behavior in the first few groups of each integration, potentially impacting absolute fluxes and transit depths on bright targets, where only a handful of groups are possible. Overall, the noise is within 50% of the theoretical photon noise and read noise. This bodes well for high-precision measurements of transiting exoplanets and other time variable targets.

Keywords: exoplanet atmospheres; space vehicle instruments; time series analysis; multiple mirror telescopes