Sazuna/UAT_keywords huggingface dataset:
XMM-Newton and NICER Measurement of the Rms Spectrum of the Millihertz Quasiperiodic Oscillations in the Neutron-star Low-mass X-Ray Binary 4U 1636-53. We used two XMM-Newton and six Neutron Star Interior Composition Explorer observations to investigate the fractional rms amplitude of the millihertz quasiperiodic oscillations (mHz QPOs) in the neutron-star low-mass X-ray binary 4U 1636-53. We studied, for the first time, the fractional rms amplitude of the mHz QPOs versus energy in 4U 1636-53 down to 0.2 keV. We find that, as the energy increases from ∼0.2 to ∼3 keV, the rms amplitude of the mHz QPOs increases, different from the decreasing trend that has been previously observed above 3 keV. This finding has not yet been predicted by any current theoretical model; however, it provides an important observational feature to speculate whether a newly discovered mHz oscillation originates from the marginally stable nuclear burning process on the neutron-star surface.

Keywords: Low-mass x-ray binary stars, Neutron stars, Astrophysical explosive burning
Physics of Pair Producing Gaps in Black Hole Magnetospheres. II. General Relativity. This is the second paper in a series where we examine the physics of pair producing gaps in low-luminosity accreting supermassive black hole systems. In this paper, we carry out time-dependent self-consistent fully general relativistic 1D particle-in-cell simulations of the gap, including full inverse Compton scattering and photon tracking. Similar to the previous paper, we find a highly time-dependent solution where a macroscopic vacuum gap can open quasiperiodically, producing bursts of ${e}^{\pm }$ pairs and high energy radiation. We present the light curve, particle spectrum, and photon spectrum from this process. Using an empirical scaling relation, we rescale the parameters to the inferred values at the base of the jet in M87, and find that the observed TeV flares could potentially be explained by this model under certain parameter assumptions.

Keywords: Black hole physics, Non-thermal radiation sources, Plasma astrophysics, High energy astrophysics
Looking at Blazar Light-curve Periodicities with Gaussian Processes. Temporal analysis of blazar flux is a powerful tool to draw inferences about the emission processes and physics of these sources. In the most general case, the available light curves are irregularly sampled and influenced by gaps, and in addition are also affected by correlated noise, making their analysis complicated. Gaussian processes may offer a viable tool to assess the statistical significance of proposed periods in light curves characterized by any sampling and noise pattern. We infer the significance of the periods proposed in the literature for two well known blazars with multiple claims of possible year-long periodicity: PG 1553 + 113 and PKS 2155-304, in the high-energy and optical bands. Adding a periodic component to the modeling gives a better statistical description of the analyzed light curves. The improvement is rather solid for PG 1553 + 113, both at high energies and in the optical, while for PKS 2155-304 at high energies the improvement is not yet strong enough to allow cogent claims, and no evidence for periodicity emerged from the analysis in the optical. Modeling a light curve by means of Gaussian processes, in spite of being relatively computationally demanding, allows us to derive a wealth of information about the data under study and suggests an original analysis framework for light curves of astrophysical interest.

Keywords: Period determination, Blazars, Astrostatistics techniques, Lomb-Scargle periodogram, Gaussian Processes regression, Time series analysis
Coronal Magnetic Field Topology from Total Solar Eclipse Observations. Measuring the global magnetic field of the solar corona remains exceptionally challenging. The fine-scale density structures observed in white-light images taken during total solar eclipses are currently the best proxies for inferring the magnetic field direction in the corona from the solar limb out to several solar radii (R⊙). We present, for the first time, the topology of the coronal magnetic field continuously between 1 and 6 R⊙, as quantitatively inferred with the rolling Hough transform for 14 unique eclipse coronae that span almost two complete solar cycles. We find that the direction of the coronal magnetic field does not become radial until at least 3 R⊙, with a high variance between 1.5 and 3 R⊙ at different latitudes and phases of the solar cycle. We find that the most nonradial coronal field topologies occur above regions with weaker magnetic field strengths in the photosphere, while stronger photospheric fields are associated with highly radial field lines in the corona. In addition, we find an abundance of field lines that extend continuously from the solar surface out to several solar radii at all latitudes, regardless of the presence of coronal holes. These results have implications for testing and constraining coronal magnetic field models, and for linking in situ solar wind measurements to their sources at the Sun.

Keywords: Solar cycle, Solar eclipses, Solar wind, Solar optical telescopes, Solar magnetic fields, Solar corona, Solar coronal holes, Solar coronal plumes, Solar coronal streamers
A Pre-main-sequence γ Dor-δ Sct Hybrid with Extremely Slow Internal Rotation in a Short-period Eclipsing Binary KIC 9850387 Revealed by Asteroseismology. A complete understanding of the formation process of close binaries relies on the reliable determination of their masses and ages, as well as the interior structure of pre-main-sequence (PMS) binaries. PMS eclipsing binaries containing stellar oscillations are therefore benchmarks since the binarity makes it possible to measure the masses and radii independently with great accuracy, while stellar oscillations represent a unique method of probing stellar interiors. Here we report the discovery of KIC 9850387, a short-period PMS eclipsing binary exhibiting hybrid γ Dor-δ Sct pulsations that is also the inner binary of a probable hierarchical triple system. From the light-curve and radial-velocity modeling we determine the masses and radii of the component stars, which suggest the probable PMS nature of the system. Based on four years of Kepler data, the intrinsic oscillations of the star are analyzed. The pulsation spectrum shows 17 low-frequency peaks spaced at exactly equidistant periods that are identified as dipole gravity modes. The practically constant period spacing indicates an extremely slow near-core rotation of the pulsator with a period deduced to be longer than 1 yr. This enables us to fit the pulsation frequencies precisely with non-rotating models. The stellar parameters yielded by asteroseismology modeling are in consistent with the dynamic ones given by the binary model. The results indicate that the pulsator is a young PMS star with an age between 6.4 and 7.1 Myr. KIC 9850387 is therefore the first PMS eclipsing binary identified by asteroseismology.

Keywords: Stellar interiors, Pre-main sequence stars, Eclipsing binary stars, Stellar oscillations, Stellar rotation
A Microlensing Accretion Disk Size Measurement in the Lensed Quasar WFI 2026-4536. We use 13 seasons of R-band photometry from the 1.2 m Leonard Euler Swiss Telescope at La Silla to examine microlensing variability in the quadruply imaged lensed quasar WFI 2026-4536. The lightcurves exhibit ∼0.2 mag of uncorrelated variability across all epochs and a prominent single feature of ∼0.1 mag within a single season. We analyze this variability to constrain the size of the quasar's accretion disk. Adopting a nominal inclination of 60°, we find an accretion disk scale radius of $\mathrm{log}({r}_{s}/\mathrm{cm})={15.74}_{-0.29}^{+0.34}$ at a rest-frame wavelength of 2043 Å, and we estimate a black hole mass of $\mathrm{log}({M}_{\mathrm{BH}}/{M}_{\odot })={9.18}_{-0.34}^{+0.39}$ , based on the C IV line in VLT spectra. This size measurement is fully consistent with the quasar accretion disk size—black hole mass relation, providing another system in which the accretion disk is larger than predicted by thin-disk theory.

Keywords: Quasar microlensing, Strong gravitational lensing, Reverberation mapping, Gravitational microlensing
The Evolution of Dust Disk Sizes from a Homogeneous Analysis of 1-10 Myr old Stars. We utilize ALMA archival data to estimate the dust disk size of 152 protoplanetary disks in Lupus (1-3 Myr), Chamaeleon I (2-3 Myr), and Upper-Sco (5-11 Myr). We combine our sample with 47 disks from Tau/Aur and Oph whose dust disk radii were estimated, as here, through fitting radial profile models to visibility data. We use these 199 homogeneously derived disk sizes to identify empirical disk-disk and disk-host property relations as well as to search for evolutionary trends. In agreement with previous studies, we find that dust disk sizes and millimeter luminosities are correlated, but show for the first time that the relationship is not universal between regions. We find that disks in the 2-3 Myr old Cha I are not smaller than disks in other regions of similar age, and confirm the Barenfeld et al. finding that the 5-10 Myr USco disks are smaller than disks belonging to younger regions. Finally, we find that the outer edge of the solar system, as defined by the Kuiper Belt, is consistent with a population of dust disk sizes which have not experienced significant truncation.

Keywords: Solar system formation, Pre-main sequence stars, Dust continuum emission, Protoplanetary disks, Open star clusters
Swift Monitoring of M51: A 38 day Superorbital Period for the Pulsar ULX7 and a New Transient Ultraluminous X-Ray Source. We present the results from a monitoring campaign made with the Neil Gehrels Swift Observatory of the M51 galaxies, which contain several variable ultraluminous X-ray sources (ULXs). The ongoing campaign started in 2018 May, and we report here on ∼1.5 yr of observations. The campaign, which consists of 106 observations, has a typical cadence of 3-6 days, and has the goal of determining the long-term X-ray variability of the ULXs. Two of the most variable sources were ULX7 and ULX8, both of which are known to be powered by neutron stars that are exceeding their isotropic Eddington luminosities by factors of up to 100. This is further evidence that neutron-star-powered ULXs are the most variable. Our two main results are, first, that ULX7 exhibits a periodic flux modulation with a period of 38 days varying over a magnitude and a half in flux from peak to trough. Since the orbital period of the system is known to be 2 days, the modulation is superorbital, which is a near-ubiquitous property of ULX pulsars. Second, we identify a new transient ULX, M51 XT-1, the onset of which occurred during our campaign, reaching a peak luminosity of ∼1040 erg s-1, before gradually fading over the next ∼200 days until it slipped below the detection limit of our observations. Combined with the high-quality Swift/X-ray Telescope lightcurve of the transient, serendipitous observations made with Chandra and XMM-Newton provide insights into the onset and evolution of a likely super-Eddington event.

Keywords: X-ray photometry, Light curves, X-ray point sources, Transient sources, Galaxy nuclei, X-ray transient sources, X-ray active galactic nuclei, X-ray bright point, Active galactic nuclei
The Low Effective Spin of Binary Black Holes and Implications for Individual Gravitational-wave Events. While the Advanced LIGO and Virgo gravitational-wave (GW) experiments now regularly observe binary black hole (BBH) mergers, the evolutionary origin of these events remains a mystery. Analysis of the BBH spin distribution may shed light on this mystery, offering a means of discriminating between different binary formation channels. Using the data from Advanced LIGO and Virgo's first and second observing runs, here we seek to carefully characterize the distribution of effective spin ${\chi }_{\mathrm{eff}}$ among BBHs, hierarchically measuring the distribution's mean μ and variance σ2 while accounting for selection effects and degeneracies between spin and other black hole parameters. We demonstrate that the known population of BBHs have spins that are both small, with μ ≈ 0, and very narrowly distributed, with σ2 ≤ 0.07 at 95% credibility. We then explore what these ensemble properties imply about the spins of individual BBH mergers, reanalyzing existing GW events with a population-informed prior on their effective spin. Under this analysis, the BBH GW170729, which previously excluded ${\chi }_{\mathrm{eff}}=0$ , is now consistent with zero effective spin at ∼10% credibility. More broadly, we find that uninformative spin priors generally yield overestimates for the effective spin magnitudes of compact binary mergers.

Keywords: Bayesian statistics, Black holes, Gravitational waves, Compact objects, LIGO
Cosmic Spin and Mass Evolution of Black Holes and Its Impact. We build an evolution model of the central black hole that depends on the processes of gas accretion, the capture of stars, mergers, and electromagnetic torque. In the case of gas accretion in the presence of cooling sources, the flow is momentum driven, after which the black hole reaches a saturated mass; subsequently, it grows only by stellar capture and mergers. We model the evolution of the mass and spin with the initial seed mass and spin in ΛCDM cosmology. For stellar capture, we have assumed a power-law density profile for the stellar cusp in a framework of relativistic loss cone theory that includes the effects of black hole spin, Carter's constant, loss cone angular momentum, and capture radius. Based on this, the predicted capture rates of 10-5 to 10-6 yr-1 are closer to the observed range. We have considered the merger activity to be effective for z ≲ 4, and we self-consistently include the Blandford-Znajek torque. We calculate these effects on the black hole growth individually and in combination, for deriving the evolution. Before saturation, accretion dominates the black hole growth (∼95% of the final mass), and subsequently stellar capture and mergers take over with roughly equal contributions. The simulations of the evolution of the M•-σ relation using these effects are consistent with available observations. We run our model backward in time and retrodict the parameters at formation. Our model will provide useful inputs for building demographics of the black holes and in formation scenarios involving stellar capture.

Keywords: Accretion, Black hole physics, Cosmological evolution, Stellar dynamics, Galaxy nuclei
A New Facility for Airborne Solar Astronomy: NASA's WB-57 at the 2017 Total Solar Eclipse. NASA's WB-57 High Altitude Research Program provides a deployable, mobile, and stratospheric platform for scientific research. Airborne platforms are of particular value for making coronal observations during total solar eclipses because of their ability both to follow the Moon's shadow and to get above most of the atmospheric air mass that can interfere with astronomical observations. We used the 2017 August 21 eclipse as a pathfinding mission for high-altitude airborne solar astronomy, using the existing high-speed visible-light and near/midwave infrared imaging suite mounted in the WB-57 nose cone. In this paper, we describe the aircraft, the instrument, and the 2017 mission; operations and data acquisition; and preliminary analysis of data quality from the existing instrument suite. We describe benefits and technical limitations of this platform for solar and other astronomical observations. We present a preliminary analysis of the visible-light data quality and discuss the limiting factors that must be overcome with future instrumentation. We conclude with a discussion of lessons learned from this pathfinding mission and prospects for future research at upcoming eclipses, as well as an evaluation of the capabilities of the WB-57 platform for future solar astronomy and general astronomical observation.

Keywords: Total eclipses, The Sun, Solar coronal heating, Solar eclipses, Solar coronal waves, Solar corona, Astronomical instrumentation, Solar instruments, Solar coronal plumes, Solar coronal streamers
The Ultraluminous Lyα Luminosity Function at z = 6.6. We present the luminosity function (LF) for ultraluminous Lyα emitting galaxies (LAEs) at z = 6.6. We define ultraluminous LAEs (ULLAEs) as galaxies with $\mathrm{log}L(\mathrm{Ly}\alpha )\gt 43.5$ erg s-1. We select our main sample using the g', r', I', z', and NB921 observations of a wide-area (30 deg2) Hyper Suprime-Cam survey of the north ecliptic pole (NEP) field. We select candidates with $g^{\prime} ,r^{\prime} ,I^{\prime} \gt 26$ , NB921 ≤ 23.5, and $\mathrm{NB}921-z^{\prime} \leqslant 1.3$ . Using the DEIMOS spectrograph on Keck II, we confirm 9 of our 14 candidates as ULLAEs at z = 6.6 and the remaining 5 as an active galactic nucleus at z = 6.6, two [O III]λ5007 emitting galaxies at z = 0.84 and z = 0.85, and two nondetections. This emphasizes the need for full spectroscopic follow-up to determine accurate LFs. In constructing the ULLAE LF at z = 6.6, we combine our nine NEP ULLAEs with two previously discovered and confirmed ULLAEs in the COSMOS field: CR7 and COLA1. We apply rigorous corrections for incompleteness based on simulations. We compare our ULLAE LF at z = 6.6 with LFs at z = 5.7 and z = 6.6 from the literature. Our data reject some previous LF normalizations and power-law indices, but they are broadly consistent with others. Indeed, a comparative analysis of the different literature LFs suggests that no LF is fully consistent with any of the others, making it critical to determine the evolution from z = 5.7 to z = 6.6 using LFs constructed in exactly the same way at both redshifts.

Keywords: Lyman-alpha galaxies, Observational cosmology, High-redshift galaxies, Emission line galaxies
A Hybrid Method of Accurate Classification for Blazars of Uncertain Type in Fermi-LAT Catalogs. Significant progress in the classification of Fermi unassociated sources has led to an increase in the number of blazars being found. The optical spectrum is effectively used to classify the blazars into two groups such as BL Lac objects and flat spectrum radio quasars (FSRQs). However, the accurate classification of the blazars without optical spectrum information, I.e., blazars of uncertain type (BCUs), remains a significant challenge. In this paper, we present a principle component analysis (PCA) and machine-learning hybrid blazars classification method. The method, based on the data from the Fermi-LAT 3FGL Catalog, first used the PCA to extract the primary features of the BCUs and then used a machine-learning algorithm to further classify the BCUs. Experimental results indicate that the use of PCA algorithms significantly improved the classification. More importantly, comparison with the Fermi-LAT 4FGL Catalog, which contains the spectral classification of those BCUs in the Fermi-LAT 3FGL Catalog, reveals that the proposed classification method in the study exhibits higher accuracy than currently established methods; specifically, 151 out of 171 BL Lac objects and 19 out of 24 FSRQs are correctly classified.

Keywords: Blazars, Classification
Global Energetics of Solar Flares. X. Petschek Reconnection Rate and Alfvén Mach Number of Magnetic Reconnection Outflows. We investigate physical scaling laws for magnetic energy dissipation in solar flares, in the framework of the Sweet-Parker model and the Petschek model. We find that the total dissipated magnetic energy Ediss in a flare depends on the mean magnetic field component Bf associated with the free energy Ef, the length scale L of the magnetic area, the hydrostatic density scale height λ of the solar corona, the Alfvén Mach number MA = V1/VA (the ratio of the inflow speed V1 to the Alfvénic outflow speed VA), and the flare duration τf, I.e., ${E}_{\mathrm{diss}}=(1/4\pi ){B}_{f}^{2}\ L\ \lambda \ {V}_{{\rm{A}}}\ {M}_{{\rm{A}}}\ {\tau }_{f}$ , where the Alfvén speed depends on the nonpotential field strength Bnp and the mean electron density ne in the reconnection outflow. Using MDI/Solar Dynamics Observatory (SDO) and AIA/SDO observations and 3D magnetic field solutions obtained with the vertical-current approximation non-linear force-free field code we measure all physical parameters necessary to test scaling laws, which represents a new method to measure Alfvén Mach numbers MA, the reconnection rate, and the total free energy dissipated in solar flares.

Keywords: Solar flares, Solar magnetic reconnection, Solar coronal loops, Solar coronal heating, Solar magnetic fields
AGN X-Ray Irradiation of CO Gas in NGC 2110 Revealed by Chandra and ALMA. We report spatial distributions of the Fe-Kα line at 6.4 keV and the CO(J = 2-1) line at 230.538 GHz in NGC 2110, which are, respectively, revealed by Chandra and Atacama Large Millimeter/submillimeter Array (ALMA) at ≈0"5. A Chandra 6.2-6.5 keV to 3.0-6.0 keV image suggests that the Fe-Kα emission extends preferentially in a northwest to southeast direction out to ≈3″, or ∼500 pc, on each side. Spatially resolved spectral analyses support this by finding significant Fe-Kα emission lines only in the northwest and southeast regions. Moreover, their equivalent widths are found to be ∼1.5 keV, indicative for the fluorescence by nuclear X-ray irradiation as the physical origin. By contrast, CO(J = 2-1) emission is weak therein. For quantitative discussion, we derive ionization parameters by following an X-ray dominated region (XDR) model. We then find them high enough to interpret the weakness as the result of X-ray dissociation of CO and/or H2. Another possibility also remains that CO molecules follow a superthermal distribution, resulting in brighter emission in higher-J lines. Further follow-up observations are encouraged to draw a conclusion on what predominantly changes the interstellar matter properties and whether the X-ray irradiation eventually affects the surrounding star formation as active galactic nucleus (AGN) feedback.

Keywords: AGN host galaxies, Molecular gas, X-ray astronomy, X-ray active galactic nuclei, Star formation, Active galactic nuclei, Submillimeter astronomy, Radio astronomy, Astrophysical black holes
KIC 10736223: An Algol-type Eclipsing Binary That Has Just Undergone the Rapid Mass-transfer Stage. This paper reports the discovery of an Algol system KIC 10736223 that just passed the rapid mass transfer stage. From the light-curve and radial-velocity modeling we find KIC 10736223 to be a detached Algol system with the less-massive secondary nearly filling its Roche lobe. Based on the short-cadence Kepler data, we analyzed intrinsic oscillations of the pulsator and identified six secured independent δ Scuti-type pulsation modes (f1, f3, f9, f19, f42, and f48). We compute two grids of theoretical models to reproduce the δ Scuti frequencies, and find that fitting results of mass-accreting models agree well with those of single-star evolutionary models. The fundamental parameters of the primary star yielded with asteroseismology are $M={1.57}_{-0.09}^{+0.05}$ M⊙, Z = 0.009 ± 0.001, $R={1.484}_{-0.028}^{+0.016}$ R⊙, $\mathrm{log}g={4.291}_{-0.009}^{+0.004}$ , ${T}_{\mathrm{eff}}={7748}_{-378}^{+230}$ K, and L = ${7.136}_{-1.519}^{+1.014}$ L⊙. The asteroseismic parameters match well with the dynamical parameters derived from the binary model. Moreover, our asteroseismic results show that the pulsator is an almost unevolved star with an age between 9.46 and 11.65 Myr for single-star evolutionary models and 2.67-3.14 Myr for mass-accreting models. Therefore, KIC 10736223 may be an Algol system that has just undergone the rapid mass-transfer process.

Keywords: Eclipsing binary stars, Stellar oscillations, Asteroseismology, Delta Scuti variable stars