adsabs/SciX_UAT_keywords huggingface dataset:
KIC 7284688: A Solar-type Eclipsing Binary with Rapidly Varying O'Connell Effect

We present comprehensive photometric and spectroscopic study of the short-period eclipsing binary KIC 7284688 based on the Kepler, TESS, and LAMOST data. The radial-velocity analysis indicates that it is a triple-lined system composed of a nearly equal-mass binary plus a line-of-sight star. The masses and radii of the components in the binary are measured to be M 1 = 1.142 ± 0.020M ⊙, R 1 = 1.204 ± 0.051R ⊙, and M 2 = 1.119 ± 0.019M ⊙, R 2 = 1.149 ± 0.052R ⊙. In addition to the eclipses, the light curves of the binary exhibit exhibit rapidly changing O'Connell effect, namely the inequality in light maxima, which could be attributed to the asynchronous rotation of the starspots. We analyzed the variability in the data of light residuals, the difference between light maxima (Max.I-Max.II) as well as the epochs of light minima and determined a rotation period of 0.644 days. Moreover, we detected a quasiperiod with ~213 days from both the data of (Max.I-Max.II) and light times of minima, which is almost identical to the beat between the rotation period (~0.644 days) and the orbital period (~0.646 days). We conclude that the quasiperiodic variations of the O'Connell on the system are probably related to the starspot migration and this is a very rapid variation compared to the magnetic cycles with timescales ranging from years to decades.

Keywords: eclipsing binary stars; stellar rotation; starspots
Four-hundred Very Metal-poor Stars Studied with LAMOST and Subaru. II. Elemental Abundances

We present homogeneous abundance analysis of over 20 elements for 385 very metal-poor (VMP) stars based on the LAMOST survey and follow-up observations with the Subaru Telescope. It is the largest high-resolution VMP sample (including 363 new objects) studied by a single program, and the first attempt to accurately determine evolutionary stages for such a large sample based on Gaia parallaxes. The sample covers a wide metallicity range from [Fe/H] ≲ -1.7 down to [Fe/H] ~ -4.3, including over 110 objects with [Fe/H] ≤ -3.0. The expanded coverage in evolutionary status makes it possible to define the abundance trends respectively for giants and turnoff stars. The newly obtained abundance data confirm most abundance trends found by previous studies, but also provide useful updates and new samples of outliers. The Li plateau is seen in main-sequence turnoff stars with -2.5 < [Fe/H] < -1.7 in our sample, whereas the average Li abundance is clearly lower at lower metallicity. Mg, Si, and Ca are overabundant with respect to Fe, showing decreasing trend with increasing metallicity. Comparisons with chemical evolution models indicate that the overabundance of Ti, Sc, and Co are not well reproduced by current theoretical predictions. Correlations are seen between Sc and α-elements, while Zn shows a detectable correlation only with Ti but not with other α-elements. The fraction of carbon-enhanced stars ([C/Fe] > 0.7) is in the range of 20%-30% for turnoff stars depending on the treatment of objects for which C abundance is not determined, which is much higher than that in giants (~8%). Twelve Mg-poor stars ([Mg/Fe] < 0.0) have been identified in a wide metallicity range from [Fe/H] ~ -3.8 through -1.7. Twelve Eu-rich stars ([Eu/Fe] > 1.0) have been discovered in -3.4 < [Fe/H] < -2.0, enlarging the sample of r-process-enhanced stars with relatively high metallicity.

Keywords: population ii stars; chemical abundances; galaxy chemical evolution
The Star Formation Across Cosmic Time (SFACT) Survey. II. The First Catalog from a New Narrowband Survey for Emission-line Objects

Star Formation Across Cosmic Time (SFACT) is a new narrowband (NB) survey designed to detect faint emission-line galaxies (ELGs) and QSOs over a broad range of redshifts. Here we present the first list of SFACT candidates from our pilot-study fields. Using the WIYN 3.5 m telescope, we are able to achieve good image quality with excellent depth and routinely detect ELGs to r = 25.0. The limiting line flux of the survey is ~1.0 × 10-16 erg s-1 cm-2. SFACT targets three primary emission lines: Hα, [O III] λ5007, and [O II] λ3727. The corresponding redshift windows allow for the detection of objects at z ~ 0-1. With a coverage of 1.50 deg2 in our three pilot-study fields, a total of 533 SFACT candidates have been detected (355 candidates deg-2). We detail the process by which these candidates are selected in an efficient and primarily automated manner, then tabulate accurate coordinates, broadband photometry, and NB fluxes for each source.

Keywords: galaxy evolution; emission line galaxies; starburst galaxies; surveys; star formation; galaxy abundances; spiral galaxies; blue compact dwarf galaxies; seyfert galaxies; dwarf galaxies; quasars
The Ages of Optically Bright Subclusters in the Serpens Star-forming Region

The Serpens Molecular Cloud is one of the most active star-forming regions within 500 pc, with over 1000 young stellar objects (YSOs) at different evolutionary stages. The ages of the member stars inform us about the star formation history of the cloud. In this paper, we develop a spectral energy distribution (SED) fitting method for nearby evolved (diskless) young stars from members of the Pleiades to estimate their ages, with a temperature scale adopted from APOGEE spectra. When compared with literature temperatures of selected YSOs in Orion, the SED fits to cool (<5000 K) stars have temperatures that differ by an average of ≲50 K and have a scatter of ~210 K for both disk-hosting and diskless stars. We then apply this method to YSOs in the Serpens Molecular Cloud to estimate ages of optical members previously identified from Gaia DR2 astrometry data. The optical members in Serpens are concentrated in different subgroups with ages from ~4 to ~22 Myr; the youngest clusters, W40 and Serpens South, are dusty regions that lack enough optical members to be included in this analysis. These ages establish that the Serpens Molecular Cloud has been forming stars for much longer than has been inferred from infrared surveys.

Keywords: young star clusters; t tauri stars; spectral energy distribution; star forming regions
Characteristic Scales of Complexity and Coherence within Interplanetary Coronal Mass Ejections: Insights from Spacecraft Swarms in Global Heliospheric Simulations

Many aspects of the 3D structure and evolution of interplanetary coronal mass ejections (ICMEs) remain unexplained. Here, we investigate two main topics: (1) the coherence scale of magnetic fields inside ICMEs, and (2) the dynamic nature of ICME magnetic complexity. We simulate ICMEs interacting with different solar winds using the linear force-free spheromak model incorporated into the EUHFORIA model. We place a swarm of ~20,000 spacecraft in the 3D simulation domain and characterize ICME magnetic complexity and coherence at each spacecraft based on the simulated time series. Our simulations suggest that ICMEs retain a lower complexity and higher coherence along their magnetic axis, but that a characterization of their global complexity requires crossings along both the axial and perpendicular directions. For an ICME of initial half angular width of 45° that does not interact with other large-scale solar wind structures, global complexity can be characterized by as little as 7-12 spacecraft separated by 25°, but the minimum number of spacecraft rises to 50-65 (separated by 10°) if interactions occur. Without interactions, ICME coherence extends for 45°, 20°-30°, 15°-30°, and 0°-10° for B, B ϕ , B θ , and B r , respectively. Coherence is also lower in the ICME west flank compared to the east flank due to Parker spiral effects. Moreover, coherence is reduced by a factor of 3-6 by interactions with solar wind structures. Our findings help constrain some of the critical scales that control the evolution of ICMEs and aid in the planning of future dedicated multispacecraft missions.

Keywords: interplanetary magnetic fields; corotating streams; solar wind; solar coronal mass ejections
PBjam: A Python Package for Automating Asteroseismology of Solar-like Oscillators

Asteroseismology is an exceptional tool for studying stars using the properties of observed modes of oscillation. So far the process of performing an asteroseismic analysis of a star has remained somewhat esoteric and inaccessible to nonexperts. In this software paper we describe PBjam, an open-source Python package for analyzing the frequency spectra of solar-like oscillators in a simple but principled and automated way. The aim of PBjam is to provide a set of easy-to-use tools to extract information about the radial and quadropole oscillations in stars that oscillate like the Sun, which may then be used to infer bulk properties such as stellar mass, radius, age, or even structure. Asteroseismology and its data analysis methods are becoming increasingly important as space-based photometric observatories are producing a wealth of new data, allowing asteroseismology to be applied in a wide range of contexts such as exoplanet, stellar structure and evolution, and Galactic population studies. * Release 1.0.0 Zenodo, doi:10.5281/zenodo.4300079.

Keywords: astronomy software; publicly available software; asteroseismology; stellar oscillations; astronomy data analysis
Pinwheel Outflow Induced by Stellar Mass Loss in a Coplanar Triple System

We develop a physical framework for interpreting complex circumstellar patterns whorled around asymptotic giant branch (AGB) stars by investigating stable, coplanar triple systems using hydrodynamic and particle simulations. The introduction of a close tertiary body causes an additional periodic variation in the orbital velocity and trajectory of the AGB star. As a result, the circumstellar outflow builds a fine non-Archimedean spiral pattern superimposed upon the Archimedean spiral produced by the outer binary alone. This fine spiral can be approximated by off-centered circular rings that become tangent to each other at the location of the Archimedean spiral. The superimposed fine pattern fades out relatively quickly as a function of distance from the center of the system, in contrast to the dominant Archimedean spiral pattern, which presents a much slower fractional density decrease with radius. The different rates of radial decrease of the density contrast in the two superimposed patterns, coupled with their different time and spatial scales, lead to an apparent, but illusory radial change in the observed pattern interval, as has been reported, for example, in CW Leo. The function describing the detailed radial dependence of the expansion velocity is different in the two patterns, which may be used to distinguish them. The shape of the circumstellar whorled pattern is further explored as a function of the orbital eccentricity and the inner companion's mass. Although this study is confined to stable, coplanar triple systems, the results are likely applicable to moderately noncoplanar systems and open interesting avenues for studying noncoplanar systems.

Keywords: asymptotic giant branch stars; binary stars; circumstellar envelopes; astronomical simulations
The First High-contrast Images of X-Ray Binaries: Detection of Candidate Companions in the γ Cas Analog RX J1744.7-2713

X-ray binaries provide exceptional laboratories for understanding the physics of matter under the most extreme conditions. Until recently, there were few, if any, observational constraints on the circumbinary environments of X-ray binaries at ~100-5000 au scales. It remains unclear how the accretion onto the compact objects or the explosions giving rise to the compact objects interact with their immediate surroundings. Here, we present the first high-contrast adaptive optics images of X-ray binaries. These observations target all X-ray binaries within ~3 kpc accessible with the Keck/NIRC2 vortex coronagraph. This paper focuses on one of the first key results from this campaign; our images reveal the presence of 21 sources potentially associated with the γ Cassiopeiae analog high-mass X-ray binary RX J1744.7-2713. By conducting different analyses-a preliminary proper motion analysis, a color-magnitude diagram, and a probability of chance alignment calculation-we found that three of these 21 sources have a high probability of being bound to the system. If confirmed, they would be in wide orbits (~450 to 2500 au). While follow-up astrometric observations will be needed in ~5-10 yr to confirm further the bound nature of these detections, these discoveries emphasize that such observations may provide a major breakthrough in the field. In fact, they would be useful not only for our understanding of stellar multiplicity, but also for our understanding of how planets, brown dwarfs, and stars can form even in the most extreme environments.

Keywords: multiple stars; infrared astronomy; x-ray binary stars; high mass x-ray binary stars; coronagraphic imaging; direct imaging
Discovery of Two Einstein Crosses from Massive Post-blue Nugget Galaxies at z > 1 in KiDS

We report the discovery of two Einstein Crosses (ECs) in the footprint of the Kilo-Degree Survey (KiDS): KIDS J232940-340922 and KIDS J122456+005048. Using integral field spectroscopy from the Multi Unit Spectroscopic Explorer at the Very Large Telescope, we confirm their gravitational-lens nature. In both cases, the four spectra of the source clearly show a prominence of absorption features, hence revealing an evolved stellar population with little star formation. The lensing model of the two systems, assuming a singular isothermal ellipsoid (SIE) with external shear, shows that: (1) the two crosses, located at redshift z = 0.38 and 0.24, have Einstein radius RE = 5.2 kpc and 5.4 kpc, respectively; (2) their projected dark matter fractions inside the half effective radius are 0.60 and 0.56 (Chabrier initial mass function); (3) the sources are ultra-compact galaxies, Re ∼ 0.9 kpc (at redshift, zs = 1.59) and Re ∼ 0.5 kpc (zs = 1.10), respectively. These results are unaffected by the underlying mass density assumption. Due to size, blue color, and absorption-dominated spectra, corroborated by low specific star formation rates derived from optical-near-infrared spectral energy distribution fitting, we argue that the two lensed sources in these ECs are blue nuggets migrating toward their quenching phase. * Based on observations with OmegaCam@VST and MUSE@VLT (Prog. ID: 0105.A-0253).

Keywords: gravitational lensing; strong gravitational lensing; galaxy formation; dark matter
Differential Rotation for Different-sized Sunspot Groups Early Observed by the OGAUC

Solar differential rotation is an important ingredient of the solar dynamo model, not only because the solar rotation profile is one of the key inputs in a solar dynamo model, but also because it imposes constraints for the solar dynamo model. In this study, we use the sunspot group catalog published by the Coimbra Astronomical Observatory for the period 1929-1941 to analyze solar rotation profiles of different-sized sunspot groups and the dependence of their annual average of the absolute latitude and annual average rotation rate on the solar cycle. The following main results are obtained: (1) smaller sunspot groups (with an area <100 millionths of the solar hemisphere (msh)) rotate faster than larger ones (with an area >500 msh); (2) different-sized sunspot groups drift toward the equator at different velocities of latitudinal drift, reflecting that they are rooted at different anchoring depths; (3) the rotation rate reaches a maximum during the minimum of the solar cycle, which seems to be independent of the size of sunspot groups. The possible mechanisms for the above results are discussed, and we infer that the differences may be due to the different anchoring depths at which flux tubes of different-sized sunspot groups are rooted, their different ages, and the different ways in which sunspot group coordinates are determined.

Keywords: solar rotation; solar activity; sunspot groups
Tests of AGN Feedback Kernels in Simulated Galaxy Clusters

In cool-core galaxy clusters with central cooling times much shorter than a Hubble time, condensation of the ambient central gas is regulated by a heating mechanism, probably an active galactic nucleus. Previous analytical work has suggested that certain radial distributions of heat input may result in convergence to a quasi-steady global state that does not substantively change on the timescale for radiative cooling, even if the heating and cooling are not locally in balance. To test this hypothesis, we simulate idealized galaxy cluster halos using the ENZO code with an idealized, spherically symmetric heat input kernel intended to emulate. Thermal energy is distributed with radius according to a range of kernels, in which total heating is updated to match total cooling every 10 Myr. Some heating kernels can maintain quasi-steady global configurations, but no kernel we tested produces a quasi-steady state with central entropy as low as those observed in cool-core clusters. The general behavior of the simulations depends on the proportion of heating in the inner 10 kpc, with low central heating leading to central cooling catastrophes, high central heating creating a central convective zone with an inverted entropy gradient, and intermediate central heating resulting in a flat central entropy profile that exceeds observations. The timescale on which our simulated halos fall into an unsteady multiphase state is proportional to the square of the cooling time of the lowest-entropy gas, allowing more centrally concentrated heating to maintain a longer-lasting steady state.

Keywords: active galactic nuclei; hydrodynamical simulations; cooling flows; galaxy clusters; agn host galaxies
ALMA Observations of Giant Molecular Clouds in M33. I. Resolving Star Formation Activities in the Giant Molecular Filaments Possibly Formed by a Spiral Shock

We report molecular line and continuum observations toward one of the most massive giant molecular clouds (GMCs), GMC-16, in M33 using ALMA with an angular resolution of 0"44 × 0"27 (∼2 pc × 1 pc). We have found that the GMC is composed of several filamentary structures in 12CO and 13CO(J = 2-1). The typical length, width, and total mass are ∼50-70 pc, ∼5-6 pc, and ∼105 M⊙, respectively, which are consistent with those of giant molecular filaments (GMFs) as seen in the Galactic GMCs. The elongations of the GMFs are roughly perpendicular to the direction of the galaxy's rotation, and several H II regions are located at the downstream side relative to the filaments with an offset of ∼10-20 pc. These observational results indicate that the GMFs are considered to be produced by a galactic spiral shock. The 1.3 mm continuum and C18O(J = 2-1) observations detected a dense clump with the size of ∼2 pc at the intersection of several filamentary clouds, which is referred to as the "hub filament," possibly formed by a cloud-cloud collision. A strong candidate for protostellar outflow in M33 has also been identified at the center of the clump. We have successfully resolved the parsec-scale local star formation activity in which the galactic scale kinematics may induce the formation of the parental filamentary clouds.

Keywords: interstellar medium; star formation; giant molecular clouds; triangulum galaxy; protostars; local group
On the Jet Production Efficiency in a Sample of the Youngest Radio Galaxies

Here we discuss the jet production efficiency in a sample of 17 young radio galaxies with measured redshifts, kinematic ages, and nuclear X-ray fluxes, for which the observed luminosities of compact jets/lobes and accretion disks correspond to the same episode of AGN activity. For the targets, we analyze the available optical data, estimating the bolometric luminosities of the accretion disks Lbol, and the black hole masses; we also derive the minimum jet kinetic luminosities, Pj. With this information we investigate the distribution of our sample in the three-dimensional space of the accretion rate λEdd &Congruent Lbol/LEdd, the nuclear X-ray luminosity LX considered here as a limit for the emission of the disk coronae, and Pj, expressing the latter two parameters either in the Eddington units, or in the units of the disk luminosity. We find that (I) the accretion rate λEdd in our sample is distributed within a narrow range λEdd ∼ 0.01-0.2; (II) the normalized jet power Pj/LEdd formally correlates with the accretion rate λEdd, with some saturation at the largest values λEdd > 0.05; (III) the jet production efficiency ηjet ≡ Pj/\dot{M}acc c2 spans a range from ηjet ≲ 10-3 up to ∼0.2 at maximum, which is below the level expected for magnetically arrested disks around maximally spinning black holes; and (IV) there is a diversification in ηjet on the hardness-intensity diagram LX/Lbol - λEdd, with the jets being produced most efficiently during the high/hard states, and suppressed during the soft states.

Keywords: non-thermal radiation sources; radio jets; active galactic nuclei; x-ray sources; radio continuum emission; emission line galaxies; radio galaxies
Dynamical Properties of Magnetized Low-angular-momentum Accretion Flows around a Kerr Black Hole

An essential factor for determining the characteristics of an accretion flow is its angular momentum. According to the angular momentum of the flow, semi-analytical analysis suggests various types of accretion solutions. It is critical to test these with numerical simulations, using the most advanced framework available (general relativistic magnetohydrodynamics), to understand how the flow changes with different angular momentum. By changing the initial condition of the accretion torus minimally, we can simulate a steady, low-angular-momentum accretion flow around a Kerr black hole. We focus primarily on the lower limits of angular momentum and find that an accretion flow with an intermediate range of angular momentum differs significantly from high- or very-low-angular-momentum flows. The intermediate-angular-momentum accretion flow has the highest density, pressure, and temperature near the black hole, making it easier to observe. We find that the density and pressure have power-law scalings ρ ∝ r n‑3/2 and p g ∝ r n‑5/2, which only hold for very-low-angular-momentum cases. With the increase in flow angular momentum, it develops a nonaxisymmetric nature. In this case, simple self-similarity does not hold. We also find that the sonic surface moves away from the innermost stable circular orbit as the angular momentum decreases. Finally, we emphasize that an intermediate-angular-momentum flow could provide a possible solution to explaining the complex observation features of the supermassive black hole Sgr A* at our galactic center.

Keywords: accretion; black hole physics; magnetohydrodynamical simulations; magnetohydrodynamics; relativistic fluid dynamics