adsabs/SciX_UAT_keywords huggingface dataset:
Dissecting the Quadruple Binary Hyad vA 351 Masses for Three M Dwarfs and a White Dwarf

We extend results first announced by Franz et al., that identified vA 351 = H346 in the Hyades as a multiple star system containing a white dwarf. With Hubble Space Telescope Fine Guidance Sensor fringe tracking and scanning, and more recent speckle observations, all spanning 20.7 years, we establish a parallax, relative orbit, and mass fraction for two components, with a period, $P=2.70\,\mathrm{yr}$ and total mass 2.1 ${{ \mathcal M }}_{\odot }$ . With ground-based radial velocities from the McDonald Observatory Otto Struve 2.1 m Telescope Sandiford Spectrograph, and Center for Astrophysics Digital Speedometers, spanning 37 years, we find that component B consists of BC, two M dwarf stars orbiting with a very short period ( ${P}_{\mathrm{BC}}=0.749$ days), having a mass ratio ${{ \mathcal M }}_{{\rm{C}}}$ / ${{ \mathcal M }}_{{\rm{B}}}$ = 0.95. We confirm that the total mass of the system can only be reconciled with the distance and component photometry by including a fainter, higher-mass component. The quadruple system consists of three M dwarfs (A, B, C) and one white dwarf (D). We determine individual M dwarf masses ${{ \mathcal M }}_{{\rm{A}}}$ = 0.53 ± 0.10 ${{ \mathcal M }}_{\odot }$ , ${{ \mathcal M }}_{{\rm{B}}}$ = 0.43 ± 0.04 ${{ \mathcal M }}_{\odot }$ , and ${{ \mathcal M }}_{{\rm{C}}}$ = 0.41 ± 0.04 ${{ \mathcal M }}_{\odot }$ . The white dwarf mass, 0.54 ± 0.04 ${{ \mathcal M }}_{\odot }$ , comes from cooling models, an assumed Hyades age of 670 Myr, and consistency with all previous and derived astrometric, photometric, and radial velocity results. Velocities from Hα and He I emission lines confirm the BC period derived from absorption lines, with similar (He I) and higher (Hα) velocity amplitudes. We ascribe the larger Hα amplitude to emission from a region each component shadows from the other, depending on the line of sight. * We dedicate this paper to John Stauffer, who died on 2021 January 29, in honor of his many contributions to the field.

Keywords: low mass stars
Measuring the Average Molecular Gas Content of Star-forming Galaxies at z = 3-4

We study the molecular gas content of 24 star-forming galaxies at z = 3-4, with a median stellar mass of 109.1 M⊙, from the MUSE Hubble Ultra Deep Field (HUDF) Survey. Selected by their Lyα λ1216 emission and HF160W-band magnitude, the galaxies show an average $\langle {\mathrm{EW}}_{\mathrm{Ly}\alpha }^{0}\rangle \approx 20$ Å, below the typical selection threshold for Lyα emitters ( ${\mathrm{EW}}_{\mathrm{Ly}\alpha }^{0}\gt 25$ Å), and a rest-frame UV spectrum similar to Lyman-break galaxies. We use rest-frame optical spectroscopy from KMOS and MOSFIRE, and the UV features observed with MUSE, to determine the systemic redshifts, which are offset from Lyα by ⟨Δv(Lyα)⟩ = 346 km s-1, with a 100 to 600 km s-1 range. Stacking 12CO J = 4 → 3 and [C I]3P1 → 3P0 (and higher-J CO lines) from the ALMA Spectroscopic Survey of the HUDF, we determine 3σ upper limits on the line luminosities of 4.0 × 108 K km s-1pc2 and 5.6 × 108 K km s-1pc2, respectively (for a 300 km s-1 line width). Stacking the 1.2 mm and 3 mm dust-continuum flux densities, we find a 3σ upper limits of 9 μJy and 1.2 μJy, respectively. The inferred gas fractions, under the assumption of a "Galactic" CO-to-H2 conversion factor and gas-to-dust ratio, are in tension with previously determined scaling relations. This implies a substantially higher αCO ≥ 10 and δGDR ≥ 1200, consistent with the subsolar metallicity estimated for these galaxies ( $12+\mathrm{log}({\rm{O}}/{\rm{H}})\approx 7.8\pm 0.2$ ). The low metallicity of z ≥ 3 star-forming galaxies may thus make it very challenging to unveil their cold gas through CO or dust emission, warranting further exploration of alternative tracers, such as [C II].

Keywords: molecular gas; high-redshift galaxies; interstellar medium; co line emission; dust continuum emission; spectroscopy
Rotation and Confined Eruption of a Double Flux-rope System

We perform a data-constrained simulation with the zero-β assumption to study the mechanisms of strong rotation and failed eruption of a filament in active region 11474 on 2012 May 5 observed by Solar Dynamics Observatory and Solar Terrestrial Relations Observatory. The initial magnetic field is provided by nonlinear force-free field extrapolation, which is reconstructed by the regularized Biot-Savart laws and magnetofrictional method. Our simulation reproduces most observational features very well, e.g., the filament large-angle rotation of about 130°, the confined eruption, and the flare ribbons, allowing us to analyze the underlying physical processes behind observations. We discover two flux ropes in the sigmoid system, an upper flux rope (MFR1) and a lower flux rope (MFR2), which correspond to the filament and hot channel in observations, respectively. Both flux ropes undergo confined eruptions. MFR2 grows by tether-cutting reconnection during the eruption. The rotation of MFR1 is related to the shear-field component along the axis. The toroidal field tension force and the nonaxisymmetry forces confine the eruption of MFR1. We also suggest that the mutual interaction between MFR1 and MFR2 contributes to the large-angle rotation and the eruption failure. In addition, we calculate the temporal evolution of the twist and writhe of MFR1, which is a hint of probable reversal rotation.

Keywords: solar filament eruptions; solar rotation; magnetic fields; solar activity; solar coronal mass ejections; magnetohydrodynamics
Tidal Asteroseismology: Possible Evidence of Nonlinear Mode Coupling in an Equilibrium State in Kepler Eclipsing Binary KIC 3230227

Previously, a series of tidally-excited oscillations were discovered in the eccentric eclipsing binary KIC 3230227. The pulsation amplitudes and phases suggest the observed oscillations are prograde quadruple modes. In this paper, we refine the analysis and extract more oscillation frequencies. We also study the temporal variations of amplitudes and phases and show that almost all modes have stable phases and amplitudes. We then focus on the non-orbital-harmonic oscillations. We consider two formation mechanisms: (1) nonlinear response of the surface convective layer, and (2) nonlinear three/multi-mode coupling. Although the former can explain some of the observed features, we find the latter mechanism is more probable. Assuming that these are coupled modes, the constant amplitude/phase over four years can be explained by either an equilibrium state in the mode coupling or modes undergoing limit cycles with very long periods. The observed frequency detuning and the calculated damping rates of the daughter modes favor the equilibrium-state interpretation. This is verified by integrating the amplitude equations of three-mode coupling. We find that the steady-state relation derived in Weinberg et al., which relates the observed frequency detuning, phase detuning, and mode damping rates, is approximately satisfied for one mode triplet. We also try to identify the azimuthal number of the modes based on the observed mode amplitude ratios and the selection rules in nonlinear three-mode coupling. We discuss further implications of these observations on nonlinear tidal asteroseismology.

Keywords: binary stars; asteroseismology; tidal interaction
Structure and Kinematics of Sh2-138-A Distant Hub-filament System in the Outer Galactic Plane

We present a molecular line study of the Sh2-138 (IRAS 22308+5812) hub-filament system with the aim of investigating its structure and kinematics. Archival CO molecular line data from the Canadian Galactic Plane Survey (CO(J = 1-0)) for the wider region (~50' × 50') and the James Clerk Maxwell Telescope (CO(3-2), 13CO(3-2), and C18O(3-2)) for the central portion (~5' × 5') have been utilized. Analysis of the CO(1-0) spectra for the extended region in conjunction with the identification of the hub and filament using a column density map and the getsf tool, respectively, reveals a complex structure with the spectral extraction for the central position displaying multiple velocity components. Based on the Herschel 70 μm warm dust emission, one of the filaments in the extended region was inferred to be associated with active star formation, and is host to a Bolocam 1.1 mm clump of ~1606 M ☉. An integrated intensity map of 13CO(3-2) emission, constructed from clumps detected at above 5σ in position-position-velocity space, reveals three filamentary structures (labeled the western filament (W-f), southwestern filament (SW-f), and southeast filament (SE-f)) in the central portion. Velocity gradients observed in 13CO(3-2) position-velocity slices point to longitudinal gas flow along the filaments into the central region. Filaments W-f, SW-f, and SE-f were calculated to have observed line masses of ~32, 33.5, and 50 M ☉ pc-1, respectively. The cloud was found to be dominated by supersonic and nonthermal motions, with high Mach numbers (≳3) and a low thermal-to-nonthermal pressure ratio (~0.01-0.1).

Keywords: interstellar medium; interstellar filaments; interstellar molecules; h ii regions; millimeter astronomy; star formation; massive stars
A Multiwavelength Study of the Highly Asymmetrical Debris Disk around HD 111520

We observed the nearly edge-on debris disk system HD 111520 at the HJ and K1 near-infrared (NIR) bands using both the spectral and polarization modes of the Gemini Planet Imager. With these new observations, we have performed an empirical analysis in order to better understand the disk morphology and its highly asymmetrical nature. We find that the disk features a large brightness and radial asymmetry, most prominent at shorter wavelengths. We also find that the radial location of the peak polarized intensity differs on either side of the star by 11 au, suggesting that the disk may be eccentric, although, such an eccentricity does not fully explain the large brightness and radial asymmetry observed. Observations of the disk halo with the Hubble Space Telescope also show the disk to be warped at larger separations, with a bifurcation feature in the northwest, further suggesting that there may be a planet in this system creating an asymmetrical disk structure. Measuring the disk color shows that the brighter extension is bluer compared to the dimmer extension, suggesting that the two sides have different dust grain properties. This finding, along with the large brightness asymmetry, are consistent with the hypothesis that a giant impact occurred between two large bodies in the northern extension of the disk, although confirming this based on NIR observations alone is not feasible. Follow-up imaging with the Atacama Large Millimeter/submillimeter Array to resolve the asymmetry in the dust mass distribution is essential in order to confirm this scenario.

Keywords: debris disks; circumstellar disks; near infrared astronomy; polarimetry
Atmospheric Dynamics on Terrestrial Planets with Eccentric Orbits

The insolation a planet receives from its parent star is the main driver of the climate and depends on the planet's orbital configuration. Planets with nonzero obliquity and eccentricity experience variations in seasonal insolation. As a result, the climate exhibits a seasonal cycle, with its strength depending on the orbital configuration and atmospheric characteristics. In this study, using an idealized general circulation model, we examine the climate response to changes in eccentricity for both zero and nonzero obliquity planets. In the zero obliquity case, a comparison between the seasonal response to changes in eccentricity and perpetual changes in the solar constant shows that the seasonal response strongly depends on the orbital period and radiative timescale. More specifically, using a simple energy balance model, we show the importance of the latitudinal structure of the radiative timescale in the climate response. We also show that the response strongly depends on the atmospheric moisture content. The combination of an eccentric orbit with nonzero obliquity is complex, as the insolation also depends on the perihelion position. Although the detailed response of the climate to variations in eccentricity, obliquity, and perihelion is involved, the circulation is constrained mainly by the thermal Rossby number and the maximum temperature latitude. Finally, we discuss the importance of different planetary parameters that affect the climate response to orbital configuration variations.

Keywords: exoplanet atmospheres; planetary atmospheres; atmospheric circulation; elliptical orbits
Cleaning Our Hazy Lens: Exploring Trends in Transmission Spectra of Warm Exoplanets

Relatively little is understood about the atmospheric composition of temperate to warm exoplanets (equilibrium temperature T eq < 1000 K), as many of them are found to have uncharacteristically flat transmission spectra. Their flattened spectra are likely due to atmospheric opacity sources such as planet-wide photochemical hazes and condensation clouds. We compile the transmission spectra of 25 warm exoplanets previously observed by the Hubble Space Telescope and quantify the haziness of each exoplanet using a normalized amplitude of the water absorption feature (A H). By examining the relationships between A H and various planetary and stellar forcing parameters, we endeavor to find correlations of haziness associated with planetary properties. We adopt new statistical correlation tests that are more suitable for the small, nonnormally distributed warm exoplanet sample. Our analysis shows that none of the parameters have a statistically significant correlation with A H (p ≤ 0.01) with the addition of new exoplanet data, including the previously identified linear trends between A H and T eq or the hydrogen-helium envelope mass fraction (f HHe). This suggests that haziness in warm exoplanets is not simply controlled by any single planetary/stellar parameter. Among all the parameters we investigated, planet gravity (g p), atmospheric scale height (H), planet density (ρ p), orbital eccentricity (e), and age of the star (t age) have tentative correlations with A H. Specifically, lower H, higher g p, ρ p, e, or t age may lead to clearer atmospheres. We still need more observations and laboratory experiments to fully understand the complex physics and chemistry involved in creating hazy warm exoplanets.

Keywords: exoplanet atmospheres; exoplanet atmospheric composition; extrasolar gaseous planets
Magnetic Flux Plays an Important Role during a Black Hole X-Ray Binary Outburst in Radiative Two-temperature General Relativistic Magnetohydrodynamic Simulations

Black hole (Bh) X-ray binaries cycle through different spectral states of accretion over the course of months to years. Although persistent changes in the Bh mass accretion rate are generally recognized as the most important component of state transitions, it is becoming increasingly evident that magnetic fields play a similarly important role. In this article, we present the first radiative two-temperature general relativistic magnetohydrodynamics simulations in which an accretion disk transitions from a quiescent state at an accretion rate of $\dot{M}\sim {10}^{-10}{\dot{M}}_{\mathrm{Edd}}$ to a hard-intermediate state at an accretion rate of $\dot{M}\sim {10}^{-2}{\dot{M}}_{\mathrm{Edd}}$ . This huge parameter space in mass accretion rate is bridged by artificially rescaling the gas density scale of the simulations. We present two jetted BH models with varying degrees of magnetic flux saturation. We demonstrate that in "standard and normal evolution" models, which are unsaturated with magnetic flux, the hot torus collapses into a thin and cold accretion disk when $\dot{M}\gtrsim 5\times {10}^{-3}{\dot{M}}_{\mathrm{Edd}}$ . On the other hand, in "magnetically arrested disk" models, which are fully saturated with vertical magnetic flux, the plasma remains mostly hot with substructures that condense into cold clumps of gas when $\dot{M}\gtrsim 1\times {10}^{-2}{\dot{M}}_{\mathrm{Edd}}$ . This suggests that the spectral signatures observed during state transitions are closely tied to the level of magnetic flux saturation.

Keywords: black holes; relativistic jets; magnetohydrodynamical simulations; hydrodynamical simulations; accretion
Supernova Interaction with a Dense Detached Shell in SN 2001em

We carry out a comprehensive analysis of supernova SN 2001em covering a period of 19 yr since discovery. SN 2001em is the oldest supernova known to have undergone a metamorphosis from a stripped envelope to an interacting supernova. An early spectrum indicates it exploded as a Type Ib supernova. Later, the ejecta caught up with a dense circumstellar H-shell, ejected a few thousand years before the explosion, triggering interaction between the supernova ejecta and the dense shell, producing radio, X-ray, and Hα emission. We use archival data with the Very Large Array in radio bands and with Chandra, XMM-Newton, and Swift-XRT in X-ray bands, along with published Hα measurements. We combine these data with our low radio frequency observations with the Giant Metrewave Radio Telescope at two epochs covering three frequencies. While the observations missed the phase when the shock entered the dense shell, the X-rays indicate that the shock came out of the dense shell at around 1750 days. The data suggest a forward shock origin of the X-ray emission. Radio data show a spectral inversion at late epochs ( $\gt 5000$ days) at around 3 GHz, which mimics the properties of the central absorbed component seen in SN 1986J. A possible explanation for this component is that the progenitor of SN 2001em was a massive binary system that had undergone a period of common-envelope evolution. The hydrogen envelope from the SN 2001em progenitor may have been lost as a result of binary interaction.

Keywords: supernovae; circumstellar matter; radio observatories; x-ray sources; non-thermal radiation sources; circumstellar shells
Quasar Microlensing Statistics and Flux-ratio Anomalies in Lens Models

Precise lens modeling is a critical step in time delay studies of multiply imaged quasars, which are key for measuring some important cosmological parameters (especially H 0). However, lens models (in particular those semi-automatically generated) often show discrepancies with the observed flux ratios between the different quasar images. These flux-ratio anomalies are usually explained through differential effects between images (mainly microlensing) that alter the intrinsic magnification ratios predicted by the models. To check this hypothesis, we collect direct measurements of microlensing to obtain the histogram of microlensing magnifications. We compare this histogram with recently published model flux-ratio anomalies and conclude that they cannot be statistically explained by microlensing. The average value of the model anomalies (0.74 mag) significantly exceeds the mean impact of microlensing (0.33 mag). Moreover, the histogram of model anomalies presents a significant tail with high anomalies (∣Δm∣ ≥ 0.7 mag), which is completely unexpected from the statistics of microlensing observations. Microlensing simulations neither predict the high mean nor the fat tail of the histogram of model anomalies. We perform several statistical tests which exclude that microlensing can explain the observed flux-ratio anomalies (although Kolmogorov–Smirnov, which is less sensitive to the tail of the distributions, is not always conclusive). Thus, microlensing cannot statistically explain the bulk of flux-ratio anomalies, and models may explore different alternatives to try to reduce them. In particular, we propose to complement photometric observations with accurate flux ratios of the broad emission lines obtained from integral field spectroscopy to check and, ideally, constrain lens models.

Keywords: gravitational lensing; gravitational microlensing
Col-OSSOS: Evidence for a Compositional Gradient Inherited from the Protoplanetary Disk?

In the present-day Kuiper Belt, the number of compositional classes and the orbital distributions of these classes hold important cosmogonic implications for the solar system. The Colours of the Outer Solar System Origins Survey (Col-OSSOS) recently showed that the observed color distribution of small (H ⪆ 6) trans-Neptunian objects (TNOs) can be accounted for by the existence of only two composition classes, named BrightIR and FaintIR, where the range of colors in each class can be modeled as mixtures of two material end-members. Here, we combine the high-precision photometric measurements of Col-OSSOS with those of previous surveys to investigate the orbital distribution of the two color classes and reinterpret the known color-inclination correlation of TNOs in the context of the BrightIR/FaintIR taxonomy. In addition to confirming the previously reported distinct orbital distributions of these classes, we identify a trend of increasing orbital inclinations toward the bluer end of the optical and near-infrared color distribution of BrightIR objects. Using the output of numerical simulations investigating the orbital evolution of TNOs during their scattering phase with Neptune, we show that this trend could reflect a composition gradient in the early protoplanetary disk, in the range of heliocentric distances over which TNOs from the BrightIR class accreted. However, tensions between this interpretation and the existence of blue contaminants among cold classical TNOs, and possible alternative origins for the detected correlation, currently bear uncertainty on our proposed interpretation.

Keywords: trans-neptunian objects; broad band photometry
Neutrino Transport with Monte Carlo Method. I. Toward Fully Consistent Implementation of Nucleon Recoils in Core-collapse Supernova Simulations

The small energy exchange via nucleon recoils in neutrino-nucleon scattering is now supposed to be one of the important factors for successful explosions of core-collapse supernovae (CCSNe), as they can change neutrino spectra through accumulation of a large number of scatterings. In deterministic methods employed for neutrino transport in CCSN simulations, we normally cannot afford to deploy a large enough number of energy bins needed to resolve this small energy exchange, and subgrid techniques are employed one way or another. In this paper, we study quantitatively with the Monte Carlo (MC) method how well such a treatment performs. We first investigate the effects of nucleon recoils on the neutrino spectra and confirm that the average energy is reduced by ∼15% for heavy-lepton neutrinos and much smaller amounts for other types of neutrinos in a typical postbounce situation. It is also observed that the nucleon scattering dominates the electron scattering in the thermalization of neutrino spectra in all flavors. We then study possible artifacts that the coarse energy grid may produce in the deterministic methods. In order to mimic the latter calculation, we redistribute MC particles in each energy bin after a certain interval in a couple of ways and study how the results are affected, depending on the energy resolution. We also discuss the possible implications of our results for the deterministic methods.

Keywords: supernova neutrinos; core-collapse supernovae