adsabs/SciX_UAT_keywords huggingface dataset:
The K2 M67 Study: Precise Mass for a Turnoff Star in the Old Open Cluster M67

We present a study of the bright detached eclipsing main-sequence binary WOCS 11028 (Sanders 617) in the open cluster M67. Although the binary has only one eclipse per orbital cycle, we show that the masses of the stars can be derived very precisely thanks to a strong constraint on the orbital inclination: MA = 1.222 ± 0.006M⊙ and MB = 0.909 ± 0.004M⊙. We use a spectral energy distribution fitting method to derive characteristics of the component stars in lieu of the precise radii that would normally be derived from a doubly eclipsing binary. The deconvolution of the SEDs reveals that the brighter component of the binary is at the faint turnoff point for the cluster—a distinct evolutionary point that occurs after the convective core has been established and while the star is in the middle of its movement toward lower surface temperatures, before the so-called hook at the end of the main sequence. The measurements are in distinct disagreement with evolution models at solar metallicity: higher metal abundances are needed to reproduce the characteristics of WOCS 11028 A. We discuss the changes to model physics that are likely to be needed to address the discrepancies. The clearest conclusions are that diffusion is probably necessary to reconcile spectroscopic abundances of M67 stars with the need for higher metallicity models and that reduced strength convective overshooting is occurring for stars at the turnoff. At super-solar bulk metallicity, various indicators agree on a cluster age between about 3.5 and 4.0 Gyr.

Keywords: open star clusters; eclipsing binary stars; spectroscopic binary stars; low mass stars; stellar convective zones; stellar diffusion
The Interferometric Binary ϵ Cnc in Praesepe: Precise Masses and Age

We observe the brightest member of the Praesepe cluster, ϵ Cnc, to precisely measure the characteristics of the stars in this binary system, en route to a new measurement of the cluster's age. We present spectroscopic radial velocity measurements and interferometric observations of the sky-projected orbit to derive the masses, which we find to be M 1/M ⊙ = 2.420 ± 0.008 and M 2/M ⊙ = 2.226 ± 0.004. We place limits on the color-magnitude positions of the stars by using spectroscopic and interferometric luminosity ratios while trying to reproduce the spectral energy distribution of ϵ Cnc. We reexamine the cluster membership of stars at the bright end of the color-magnitude diagram using Gaia data and literature radial velocity information. The binary star data are consistent with an age of 637 ± 19 Myr, as determined from MIST model isochrones. The masses and luminosities of the stars appear to select models with the most commonly used amount of convective core overshooting.

Keywords: open star clusters; spectroscopic binary stars; white dwarf stars; stellar evolution; long baseline interferometry
Noninteracting Black Hole Binaries with Gaia and LAMOST

Until recently, black holes (BHs) could be discovered only through accretion from other stars in X-ray binaries, or in merging double compact objects. Improvements in astrometric and spectroscopic measurements have made it possible to detect BHs also in noninteracting BH binaries (nBHBs) through a precise analysis of the companion's motion. In this study, using an updated version of the StarTrack binary-star population modeling code and a detailed model of the Milky Way (MW) galaxy, we calculate the expected number of detections for Gaia and LAMOST surveys. We develop a formalism to convolve the binary population synthesis output with a realistic stellar density distribution, star formation history (SFH), and chemical evolution for the MW, which produces a probability distribution function of the predicted compact-binary population over the MW. This avoids the additional statistical uncertainty that is introduced by methods that Monte Carlo sample from binary population synthesis output to produce one potential specific realization of the MW compact-binary distribution, and our method is also comparatively fast to such Monte Carlo realizations. Specifically, we predict ∼41-340 nBHBs to be observed by Gaia, although the numbers may drop to ∼10-70 if the recent (≲100 Myr) star formation is low (∼1 M⊙ yr-1). For LAMOST we predict ≲14 detectable nBHBs, which is lower partially because its field of view covers just ∼6% of the Galaxy.

Keywords: stellar mass black holes; binary stars; gravitational wave sources; astrometric binary stars; spectroscopic binary stars; astrostatistics; markov chain monte carlo; computational astronomy; astronomy databases
Ultraviolet Line Identifications and Spectral Formation Near Max Light in Type Ia Supernova 2011fe

We present ultraviolet line identifications of near maximum-light Hubble Space Telescope observations of SN 2011fe using synthetic spectra generated from both SYNOW and PHOENIX. We find the spectrum to be dominated by blends of iron group elements Fe, Co, and Ni (as expected due to heavy line blanketing by these elements in the UV) and for the first time identify lines from C IV and Si IV in a supernova spectrum. We also find that classical delayed detonation models of SNe Ia are able to accurately reproduce the flux levels of SN 2011fe in the UV. Further analysis reveals that photionization edges play an important role in feature formation in the far-UV, and that temperature variations in the outer layers of the ejecta significantly alter the Fe III/Fe II ratio producing large flux changes in the far-UV and velocity shifts in mid-UV features. SN 2011fe is the best observed core-normal SNe Ia; therefore analysis of its UV spectra shows the power of UV spectra in discriminating between different metallicities and progenitor scenarios of SNe Ia, due to the fact that the UV probes the outermost layers of the SN Ia, which are most sensitive to metallicity and progenitor variations.

Keywords: type ia supernovae; supernovae
HIFLOW: Generating Diverse HI Maps and Inferring Cosmology while Marginalizing over Astrophysics Using Normalizing Flows

A wealth of cosmological and astrophysical information is expected from many ongoing and upcoming large-scale surveys. It is crucial to prepare for these surveys now and develop tools that can efficiently extract most information. We present HIFLOW: a fast generative model of the neutral hydrogen (HI) maps that is conditioned only on cosmology (Ω m and σ 8) and designed using a class of normalizing flow models, the masked autoregressive flow. HIFLOW is trained on the state-of-the-art simulations from the Cosmology and Astrophysics with MachinE Learning Simulations (CAMELS) project. HIFLOW has the ability to generate realistic diverse maps without explicitly incorporating the expected two-dimensional maps structure into the flow as an inductive bias. We find that HIFLOW is able to reproduce the CAMELS average and standard deviation HI power spectrum within a factor of ≲2, scoring a very high R 2 > 90%. By inverting the flow, HIFLOW provides a tractable high-dimensional likelihood for efficient parameter inference. We show that the conditional HIFLOW on cosmology is successfully able to marginalize over astrophysics at the field level, regardless of the stellar and AGN feedback strengths. This new tool represents a first step toward a more powerful parameter inference, maximizing the scientific return of future HI surveys, and opening a new avenue to minimize the loss of complex information due to data compression down to summary statistics.

Keywords: reionization; early universe; cosmological parameters; intergalactic medium; bayesian statistics
Discovery of A Large-scale Bent Radio Jet in the Merging Cluster A514

We report a discovery of a large-scale bent radio jet in the merging galaxy cluster A514 (z = 0.071). The radio emission originates from the two radio lobes of the active galactic nucleus (AGN) located near the center of the southern subcluster and extends toward the southern outskirts with multiple bends. Its peculiar morphology is characterized by a 400 kpc "bridge," a 300 kpc "arc," and a 400 kpc "tail," which together contribute to its largest linear size of ~0.7 Mpc. We find that both the flux and spectral features of the emission change with the distance from the AGN. Also, the "bridge" presents a 60% polarized radio emission, which coincided with an X-ray cold front. Based on our multiwavelength observations, we propose that A514 presents a clear case for the redistribution of an old AGN plasma due to merger-driven gas motions. We support our interpretation with idealized cluster merger simulations employing a passive tracer field to represent cosmic-ray electrons and find that merger-driven motions can efficiently create a cloud of these particles in the cluster outskirts, which later can be reaccelerated by the cluster merger shock and produce radio relics.

Keywords: galaxy clusters; abell clusters; radio jets
Hidden Water in Magma Ocean Exoplanets

We demonstrate that the deep volatile storage capacity of magma oceans has significant implications for the bulk composition, interior, and climate state inferred from exoplanet mass and radius data. Experimental petrology provides the fundamental properties of the ability of water and melt to mix. So far, these data have been largely neglected for exoplanet mass-radius modeling. Here we present an advanced interior model for water-rich rocky exoplanets. The new model allows us to test the effects of rock melting and the redistribution of water between magma ocean and atmosphere on calculated planet radii. Models with and without rock melting and water partitioning lead to deviations in planet radius of up to 16% for a fixed bulk composition and planet mass. This is within the current accuracy limits for individual systems and statistically testable on a population level. Unrecognized mantle melting and volatile redistribution in retrievals may thus underestimate the inferred planetary bulk water content by up to 1 order of magnitude.

Keywords: exoplanet structure; exoplanet atmospheres; planetary interior; mantle; extrasolar rocky planets; exoplanets; ocean planets; planetary structure
Precise Estimation of Source Intensity for Wide-field Telescopes with PSF Modeling

Wide-field small aperture optical telescopes are widely used in large-scale surveys currently and they have made great contributions in a number of astronomical applications. However, specific challenges arise owing to the defects caused by the optical system, and the image quality and reduction precision are negatively affected. An innovative method is proposed to address these challenges and achieve a high-precision source intensity estimation. In implementation, first a dedicated pipeline is developed to investigate the point-spread function (PSF) components from large amounts of images, using principal component analysis. Then the PSF model that reveals the actual characteristics of the optical system is constructed based on the evaluation. Last the equations for centroid and intensity estimation are constructed and the results are obtained. A trial of observations is performed with a wide-field small aperture telescope, and a large number of raw images, as well as simulated images, are acquired to test the efficiency of our method. The intensity measurement is performed with our method and other common algorithms, including the modified moment, Gaussian fitting, and SExtractor. Based on the comparison it is demonstrated that our proposed method outperforms the others. The results indicate that our method explores the limitations of such a system and additional gains can be achieved in wider applications.

Keywords: astrometry; astronomical techniques; magnitude; ccd observation; photometry
A Type Ia Supernova near a Globular Cluster in the Early-type Galaxy NGC 5353

No progenitor of a Type Ia supernova (SN Ia) is known, but in old-population early-type galaxies, one may find SNe Ia associated with globular clusters, yielding a population age and metallicity. It also provides insight into the formation path and the SN enhancement rate in globular clusters. We sought to find such associations and identified SN 2019ein to be within the ground-based optical positional uncertainty of a globular cluster candidate within the early-type galaxy NGC 5353 at D ≈ 30 Mpc. We reduced the positional uncertainties by obtaining Hubble Space Telescope images with the Advanced Camera for Surveys, using filters F475W and F814W obtained in 2020 June. We find that the globular cluster candidate has a magnitude, color, and angular extent that are consistent with it being a typical globular cluster. The separation between the globular cluster and SN 2019ein is 0.″43, or 59 pc in projection. The chance occurrence with a random globular cluster is ≈3%, favoring but not proving an association. If the SN progenitor originated in the globular cluster, one scenario is that SN 2019ein was previously a double-degenerate white dwarf binary that was dynamically ejected from the globular cluster and exploded within 10 Myr; models do not predict this to be common. Another, but less likely scenario is where the progenitor remained bound to the globular cluster, allowing the double-degenerate binary to inspiral on a much longer timescale before producing an SN.

Keywords: type ia supernovae
Survey of Magnetic Field Parameters Associated with Large Solar Flares

Until now, how the magnetic fields in M/X-class flaring active regions (ARs) differ from C-class flaring ARs remains unclear. Here, we calculate the key magnetic field parameters within the area of high photospheric free energy density (HED region) for 323 ARs (217 C- and 106 M/X-flaring ARs), including total photospheric free magnetic energy density E free, total unsigned magnetic flux ΦHED, mean unsigned current helicity h c , length of the polarity inversion lines L PIL with a steep horizontal magnetic gradient, etc., and compare these with flare/coronal mass ejection (CME) properties. We first show the quantitative relations among the flare intensity, the eruptive character, and ΦHED. We reveal that ΦHED is a measure for the GOES flux upper limit of the flares in a given region. For a given ΦHED, there exists the lower limit of F SXR for eruptive flares. This means that only the relatively strong flares with the large fraction of energy release compared to the total free energy are likely to generate a CME. We also find that the combinations of E free–L PIL and E free–h c present a good ability to distinguish between C-class and M/X-class flaring ARs. Using determined critical values of E free and L PIL, one predicts correctly 93 out of 106 M/X-class flaring ARs and 159 out of 217 C-class flaring ARs. The large L PIL or h c for M/X-class flaring ARs probably implies the presence of a compact current with twisted magnetic fields winding about it.

Keywords: solar activity; solar flares; solar coronal mass ejections; solar active region magnetic fields
Return of the TEDI: Revisiting the Triple Evolution Dynamical Instability Channel in Triple Stars

Triple-star systems exhibit a phenomenon known as triple evolution dynamical instability (TEDI), in which mass loss in evolving triples triggers short-term dynamical instabilities, potentially leading to collisions of stars, exchanges, and ejections. Previous work has shown that the TEDI is an important pathway to head-on stellar collisions in the Galaxy, significantly exceeding the rate of collisions due to random encounters in globular clusters. Here, we revisit the TEDI evolutionary pathway using state-of-the-art population synthesis methods that self-consistently take into account stellar evolution and binary interactions as well as gravitational dynamics and perturbations from passing stars in the field. We find Galactic TEDI-induced collision rates on the order of 10-4 yr-1, consistent with previous studies which were based on more simplified methods. The majority of TEDI-induced collisions involve main-sequence stars, potentially producing blue straggler stars. Collisions involving more evolved stars are also possible, potentially producing eccentric post-common-envelope systems, and white dwarfs collisions leading to Type Ia supernovae (although the latter with a negligible contribution to the Galactic rate). In our simulations, the TEDI is not only triggered by adiabatic wind mass loss, but also by Roche lobe overflow in the inner binary: when the donor star becomes less massive than the accretor, the inner binary orbit widens, triggering triple dynamical instability. We find that collision rates are increased by ~17% when flybys in the field are taken into account. In addition to collisions, we find that the TEDI produces ~10-4 yr-1 of unbound stars, although none with escape speeds in excess of 103 km s-1.

Keywords: stellar evolution; stellar dynamics; stellar mergers
Rotational Velocities of Am and Non-chemical-peculiar Stars Based on Kepler and LAMOST DR5

Rotation is a critical physical process operating in the formation of Am stars. There is a strong correlation between low-velocity rotation and chemical peculiarity. However, the existence of many non-chemical-peculiar slow rotators challenges the understanding of Am stars. The purpose of our work is to search for low-velocity rotating non-chemical-peculiar A-type stars and Am stars and to make a comparative analysis. In this paper, we pick out a sample from the LAMOST-Kepler project, including 21 Am stars, 125 non-chemical-peculiar slow rotators, and 53 non-chemical-peculiar fast rotators. We calculate the rotational frequencies through a periodic change of light curves caused by inhomogeneous stellar surfaces and then obtain the rotational velocities. For slow rotators, the age of Am stars is statistically younger than that of non-chemical-peculiar stars in the same temperature bin. In the comparison of the period, the average amplitude, and stellar mass of Am and non-chemical-peculiar stars, we discover that there is no difference in the photometric variability between Am and non-chemical-peculiar stars, which implies similar inhomogeneities on the surfaces. The average amplitude of non-chemical-peculiar stars has a downward trend with the increase of effective temperature and stellar mass, which is consistent with the theoretical prediction caused by weak dynamo-generated magnetic fields in A-type stars. In addition, we confirm four non-chemical-peculiar stars that have flares by checking field-of-view images, pixel images, and pixel-level light curves.

Keywords: chemically peculiar stars
Impact of Ordered and Disordered Magnetic Fields on Multiwavelength Emission of Blazars

We present a detailed analysis of the effects of magnetic field topology on the spectral energy distribution (SED) and spectral variability patterns (SVPs) of blazars. In order to study these effects, we have extended our time-dependent leptonic jet model (in the internal shock scenario) to include the dependence of the synchrotron emissivity on the angle between the photon direction and the magnetic field in the plasma frame. We have explored the effects of different magnetic field geometries, such as parallel, perpendicular, oblique, toroidal, and helical, on the simulated SEDs and SVPs of a generic blazar for both purely ordered and disordered components of fields. These considerations provide either upper or lower limits to the impact on blazar emission, depending on the fraction of a disordered component present and the viewing angle. The results of our work point out some of the signatures that the orientations can leave on the SEDs and SVPs of a blazar. For example, in the case of a purely oblique field, if the magnetic field is aligned along the line of sight (in the plasma frame), it results in an annulment of the synchrotron component while keeping the flux level of the high-energy component intact. On the other hand, in the presence of a disordered component, the impact of an oblique field is reduced, and the same effect is not observed.

Keywords: blazars; radiative processes; radiative transfer; hydrodynamical simulations; relativistic jets; shocks; plasma astrophysics; active galactic nuclei; radiative transfer equation; high energy astrophysics; radiative transfer simulations; magnetic fields
Hard X-Ray Emission Associated with White Dwarfs. IV. Signs of Accretion from Substellar Companions

With an effective temperature of ≃200,000 K, KPD 0005+5106 is one of the hottest white dwarfs (WDs). ROSAT unexpectedly detected "hard" (∼1 keV) X-rays from this apparently single WD. We have obtained Chandra observations that confirm the spatial coincidence of this hard X-ray source with KPD 0005+5106. We have also obtained XMM-Newton observations of KPD 0005+5106, as well as PG 1159-035 and WD 0121-756, which are also apparently single and whose hard X-rays were detected by ROSAT at 3σ-4σ levels. The XMM-Newton spectra of the three WDs show remarkably similar shapes that can be fitted by models including a blackbody component for the stellar photospheric emission, a thermal plasma emission component, and a power-law component. Their X-ray luminosities in the 0.6-3.0 keV band range from 4 × 1029 to 4 × 1030 erg s-1. The XMM-Newton EPIC-pn soft-band (0.3-0.5 keV) light curve of KPD 0005+5106 is essentially constant, but the hard-band (0.6-3.0 keV) light curve shows periodic variations. An analysis of the generalized Lomb-Scargle periodograms for the XMM-Newton and Chandra hard-band light curves finds a convincing modulation (false-alarm probability of 0.41%) with a period of 4.7 ± 0.3 hr. Assuming that this period corresponds to a binary orbital period, the Roche radii of three viable types of companion have been calculated: M9V star, T brown dwarf, and Jupiter-like planet. Only the planet has a size larger than its Roche radius, although the M9V star and T brown dwarf may be heated by the WD and inflate past the Roche radius. Thus, all three types of companion may be donors to fuel accretion-powered hard X-ray emission.

Keywords: white dwarf stars; x-ray stars
Relation between the Local Width and Linear Halo Mass Density of Cosmic Filaments

Large-scale cosmic filaments may have played an important role in shaping the properties of galaxies. Meanwhile, cosmic filaments are believed to harbor a substantial portion of the missing baryons at redshift z < 2. To inspect the role of filaments in these issues, many properties of filaments need to be examined, including their lengths, thicknesses, and density profiles. However, measuring some of these properties poses challenges. This study concentrates on estimating filament width/thickness, investigating potential correlations between the local width of filaments and the properties of dark matter halos within filaments. We find that the local width of filaments generally increases with the mass of dark matter halos embedded in filaments per unit length, roughly following a second-order polynomial, although with notable scatter. We probe and discuss means that may refine our findings. After further verification and improvements, this relation could be applied to filament samples constructed from the observed galaxy distribution, aiding in understanding the roles of cosmic filaments in galaxy evolution and uncovering the missing baryons.

Keywords: large-scale structure of the universe; cosmic web; hydrodynamical simulations