Sazuna/UAT_keywords huggingface dataset:
On the Power to Constrain the Accretion History of Massive Black Holes via Spin Measurements by Upcoming X-Ray Telescopes. The spin distribution of massive black holes (MBHs) contains rich information on their assembly history. However, only limited information can be extracted from currently available spin measurements of MBHs owing to the small sample size and large measurement uncertainties. Upcoming X-ray telescopes with improved spectral resolution and larger effective area are expected to provide new insights into the growth history of MBHs. Here we investigate, at a proof of concept level, how stringent constraints can be placed on the accretion history of MBHs by the spin measurements from future X-ray missions. We assume a toy model consisting of a two-phase accretion history composed of an initial coherent phase with a constant disk orientation, followed by a chaotic phase with random disk orientations in each accretion episode. By utilizing mock spin data generated from such models and performing Bayesian Markov Chain Monte Carlo simulations, we find that most accretion models of MBHs can be reconstructed provided that $\gtrsim 100$ MBH spins are measured with an accuracy of $\lesssim 0.1$ . We also quantify the precision of the reconstructed parameters by adopting various combinations of sample sizes and spin accuracies, and find that the sample size is more crucial to model reconstruction once the spin accuracy reaches ∼0.1. To some extent, a better spin accuracy will compensate for a small sample size and vice versa. Future X-ray missions such as the Advanced Telescope for High Energy Astrophysics and the enhanced X-ray Timing and Polarimetry mission, may provide spin measurements of ≳100 MBHs with an uncertainty of ∼0.04-0.1 and will thus put strong constraints on the MBH growth history.

Keywords: Accretion, Black hole physics, Supermassive black holes, X-ray detectors, Active galaxies, Galaxy nuclei
An Experimental and Theoretical Investigation into the Formation of Ketene (H<SUB>2</SUB>CCO) and Ethynol (HCCOH) in Interstellar Analog Ices. The formation of isomers of C2H2O—ketene (H2CCO), ethynol (HCCOH), and oxirene (c-CHCHO)—was investigated in interstellar ice analogs composed of carbon monoxide and water. Using tunable photoionization time-of-flight mass spectrometry to selectively ionize the isomer of interest, ketene and ethynol were detected as reaction products, but oxirene remains elusive. These findings demonstrate that organic compounds that are precursors to complex organic molecules can form without an organic source of carbon. Furthermore, we report the first plausible detection of ethynol in astrophysically relevant ices. These investigations were supported by theoretical calculations describing reaction energies, pathways, ionization energies, and harmonic frequencies.

Keywords: Interstellar molecules, Laboratory astrophysics, Chemical abundances, Astrochemistry, Interdisciplinary astronomy
Testing Rotating Regular Metrics as Candidates for Astrophysical Black Holes. The Event Horizon Telescope, a global submillimeter wavelength very long baseline interferometry array, produced the first image of supermassive black hole M87* showing a ring of diameter θd = 42 ± 3 μas, inferred a black hole mass of M = (6.5 ± 0.7) × 109M⊙, and allowed us to investigate the nature of strong-field gravity. The observed image is consistent with the shadow of a Kerr black hole, which according to the Kerr hypothesis describes the background spacetimes of all astrophysical black holes. The hypothesis, a strong-field prediction of general relativity, may be violated in the modified theories of gravity that admit non-Kerr black holes. Here, we use the black hole shadow to investigate the constraints when rotating regular black holes (non-Kerr) can be considered as astrophysical black hole candidates, paying attention to three leading regular black hole models with additional parameters g related to nonlinear electrodynamics charge. Our interesting results based on the systematic bias analysis are that rotating regular black holes shadows may or may not capture Kerr black hole shadows, depending on the values of the parameter g. Indeed, the shadows of Bardeen black holes (g ≲ 0.26M), Hayward black holes (g ≲ 0.65M) and non-singular black holes (g ≲ 0.25M) are indistinguishable from Kerr black hole shadows within the current observational uncertainties, and thereby they can be strong viable candidates for the astrophysical black holes. Whereas Bardeen black holes (g ≤ 0.30182M), Hayward black holes (g ≤ 0.73627M), and non-singular black holes (g ≤ 0.30461M), within the 1σ region for θd = 39 μas, are consistent with the observed angular diameter of M87*.

Keywords: Gravitational lensing, Black hole physics, Supermassive black holes, General relativity
The Ups and Downs of Accreting X-Ray Pulsars: Decade-long Observations with the Fermi Gamma-Ray Burst Monitor. We review more than 10 yr of continuous monitoring of accreting X-ray pulsars with the all-sky Gamma-ray Burst Monitor (GBM) aboard the Fermi Gamma-ray Space Telescope. Our work includes data from the start of GBM operations in 2008 August, through to 2019 November. Pulsations from 39 accreting pulsars are observed over an energy range of 10-50 keV by GBM. The GBM Accreting Pulsars Program performs data reduction and analysis for each accreting pulsar and makes histories of the pulse frequency and pulsed flux publicly available. We examine in detail the spin histories, outbursts, and torque behaviors of the persistent and transient X-ray pulsars observed by GBM. The spin period evolution of each source is analyzed in the context of disk-accretion and quasi-spherical settling accretion-driven torque models. Long-term pulse frequency histories are also analyzed over the GBM mission lifetime and compared to those available from the previous Burst and Transient Source Experiment all-sky monitoring mission, revealing previously unnoticed episodes in some of the analyzed sources (such as a torque reversal in 2S 1845-024). We obtain new, or update known, orbital solutions for three sources. Our results demonstrate the capabilities of GBM as an excellent instrument for monitoring accreting X-ray pulsars and its important scientific contribution to this field.

Keywords: Neutron stars, X-ray transient sources, Stellar accretion disks, Accretion
Sources of Bipolar Outflows and Model Challenges for the Egg Nebula. The striking features of the Egg Nebula—searchlight beams that illuminate a pair of bipolar lobes, quadrupolar outflows, and arcs imprinted on an expanding spherical envelope—have long defied a coherent explanation. Here we present images at high angular resolutions of emission from dust and dense molecular gas in the nebula. Away from the systemic velocity, the molecular gas primarily traces the walls of the bipolar lobes, where bipolar outflows collide with the envelope ejected by the progenitor AGB star. At and close to the systemic velocity, both the molecular gas and dust trace the walls of a cylindrical channel swept aside by these bipolar outflows; in addition, the dust also traces a channel orthogonal to the bipolar lobes, swept aside by the orthogonal set of bipolar outflows. Close to the center, the dense gas traces an expanding spherical shell, corresponding to a very dense final puff from the progenitor AGB star. The center of this shell lies within the channel aligned with the optical lobes but is displaced to the south of the channel orthogonal to these lobes, and it closely coincides with the illumination center of the nebula (location of post-AGB star), as well as the expansion center of the bipolar lobes. We highlight difficulties faced by models whereby a binary companion both induces arcs in the wind of the progenitor AGB star and gives rise to the quadrupolar outflows. Instead, we suggest that the addition of a second companion, thus forming a triple-star system, can naturally produce all the features seen.

Keywords: Circumstellar envelopes, Asymptotic giant branch stars, Planetary nebulae, Stellar mass loss
Supernova Hydrodynamics: A Lab-scale Study of the Blast-driven Instability Using High-speed Diagnostics. A novel experimental approach to study the blast-driven instability at a nondiffuse, gaseous interface with a density gradient is presented. Under Euler similarity, this approach enables study of dissipative-scale hydrodynamics relevant to many astrophysical and laboratory high energy density phenomena in a well-resolved manner. The instability is initiated by passing a Taylor-Sedov blast wave originating from a controlled detonation through a perturbed and stably stratified interface between two gases. The facility and driving blast wave are characterized to obtain repeatable conditions and capture large ensembles of time-resolved Mie scattering imaging that show consistent hydrodynamic development. We analyze the instability evolution between different gas pairs to demonstrate the wide range of development and turbulent behavior that may occur between different supernova layers. The mean evolution of the hydrodynamic instability is compared to a buoyancy-drag model that is frequently used to estimate perturbation growth in supernova mixing research. We propose a time delay to this model in order to reproduce the measured instability behavior and demonstrate model robustness in handling flows driven by a time-varying acceleration.

Keywords: Interdisciplinary astronomy, Ejecta, Hydrodynamics, Core-collapse supernovae, Laboratory astrophysics, Experimental techniques, Shocks, Supernovae, Astrophysical fluid dynamics, Supernova dynamics
Large Population of ALMA Galaxies at z &gt; 6 with Very High [O III] 88 μm to [C II] 158 μm Flux Ratios: Evidence of Extremely High Ionization Parameter or PDR Deficit?. We present our new Atacama Large Millimeter/Submillimeter Array (ALMA) observations targeting [O III]88 μm, [C II]158 μm, [N II]122 μm, and dust-continuum emission for three Lyman break galaxies at z = 6.0293-6.2037, identified in the Subaru/Hyper Suprime-Cam survey. We clearly detect [O III] and [C II] lines from all of the galaxies at 4.3-11.8σ levels, and identify multi-band dust-continuum emission in two of the three galaxies, allowing us to estimate infrared luminosities and dust temperatures simultaneously. In conjunction with previous ALMA observations for six galaxies at z &gt; 6, we confirm that all the nine z = 6-9 galaxies have high [O III]/[C II] ratios of ${L}_{[{\rm{O}}{\rm{III}}]}/{L}_{[{\rm{C}}{\rm{II}}]}\sim 3\mbox{--}20$, ∼10 times higher than z ∼ 0 galaxies. We also find a positive correlation between the [O III]/[C II] ratio and the Lyα equivalent width (EW) at the ∼90% significance level. We carefully investigate physical origins of the high [O III]/[C II] ratios at z = 6-9 using Cloudy, and find that high density of the interstellar medium, low C/O abundance ratio, and the cosmic microwave background attenuation are responsible to only a part of the z = 6-9 galaxies. Instead, the observed high [O III]/[C II] ratios are explained by 10-100 times higher ionization parameters or low photodissociation region (PDR) covering fractions of 0%-10%, both of which are consistent with our [N II] observations. The latter scenario can be reproduced with a density-bounded nebula with PDR deficit, which would enhance the Lyα, Lyman continuum, and ${{\rm{C}}}^{+}$ ionizing photons escape from galaxies, consistent with the [O III]/[C II]-Lyα EW correlation we find.

Keywords: Galaxy evolution
Significance of Gravitational Nonlinearities on the Dynamics of Disk Galaxies. The discrepancy between the visible mass in galaxies or galaxy clusters and that inferred from their dynamics is well known. The prevailing solution to this problem is dark matter. Here we show that a different approach, one that conforms to both the current standard model of particle physics and general relativity (GR), explains the recently observed tight correlation between the galactic baryonic mass and the measured accelerations in the galaxy. Using direct calculations based on GR's Lagrangian and parameter-free galactic models, we show that the nonlinear effects of GR make baryonic matter alone sufficient to explain this observation. Our approach also shows that a specific acceleration scale dynamically emerges. It agrees well with the value of the MOND acceleration scale.

Keywords: General relativity, Dark matter, Spiral galaxies
A Comparison of X-Ray Photon Indices among the Narrow- and Broad-line Seyfert 1 Galaxies. We present a detailed comparative systematic study using a sample of 221 narrow-line Seyfert 1 (NLSy1) galaxies in comparison to a redshift-matched sample of 154 broad-line Seyfert 1 (BLSy1) galaxies based on their observations using ROSAT and/or XMM-Newton in soft X-ray band (0.1-2.0 keV). A homogeneous analysis is carried out to estimate their soft X-ray photon indices ( ${{\rm{\Gamma }}}_{X}^{s}$ ) and its correlations with other parameters of nuclear activities such as Eddington ratios (REdd), bolometric luminosities (Lbol), black hole masses (MBH), and the widths of the broad component of Hβ lines (FWHM(Hβ)). In our analysis, we found clear evidence of the difference in the ${{\rm{\Gamma }}}_{X}^{s}$ and REdd distributions among NLSy1 and BLSy1 galaxies, with steeper ${{\rm{\Gamma }}}_{X}^{s}$ and higher REdd for the former. Such a difference also exists in the spectral index distribution in hard X-ray ( ${{\rm{\Gamma }}}_{X}^{h}$ ), based on the analysis of 53 NLSy1 and 46 BLSy1 galaxies in the 2-10 keV energy band. The difference in REdd distributions does exist even after applying the average correction for the difference in the inclination angle of NLSy1 and BLSy1 galaxies. We also estimated REdd, based on SED fitting of 34 NLSy1 and 30 BLSy1 galaxies over the 0.3-10 keV energy band, and found that results are still consistent with REdd estimates based on the optical bolometric luminosity. Our analysis suggests that the higher REdd in NLSy1 is responsible for its steeper X-ray spectral slope compared to the BLSy1, consistent with the disk-corona model as proposed for the luminous AGNs.

Keywords: Galaxy physics, Galaxy accretion disks, Active galaxies, Seyfert galaxies, Active galactic nuclei, X-ray surveys
The Effect of Seafloor Weathering on Planetary Habitability. Conventionally, a habitable planet is one that can support liquid water on its surface. Habitability depends on temperature, which is set by insolation and the greenhouse effect, due mainly to CO2 and water vapor. The CO2 level is increased by volcanic outgassing and decreased by continental and seafloor weathering. Here, I examine the climate evolution of Earth-like planets using a globally averaged climate model that includes both weathering types. Climate is sensitive to the relative contributions of continental and seafloor weathering, even when the total weathering rate is fixed. Climate also depends strongly on the dependence of seafloor weathering on CO2 partial pressure. Both these factors are uncertain. Earth-like planets have two equilibrium climate states: (I) an ice-free state where outgassing is balanced by both weathering types, and (II) an ice-covered state where outgassing is balanced by seafloor weathering alone. The second of these has not been explored in detail before. For some planets, neither state exists, and the climate cycles between ice-covered and ice-free states. For some other planets, both equilibria exist, and the climate depends on the initial conditions. Insolation increases over time due to stellar evolution, so a planet usually encounters the ice-covered equilibrium first. Such a planet will remain ice covered, even if the ice-free state appears subsequently, unless the climate receives a large perturbation. The ice-covered equilibrium state covers a large fraction of phase space for Earth-like planets. Many planets conventionally assigned to a star's habitable zone may be rendered uninhabitable as a result.

Keywords: Ocean-atmosphere interactions, Earth (planet), Astrobiology, Habitable zone, Habitable planets, Land-atmosphere interactions
A Fully Self-consistent Model for Solar Flares. The "standard solar flare model" collects all physical ingredients identified by multiwavelength observations of our Sun: magnetic reconnection, fast particle acceleration, and the resulting emission at various wavelengths, especially in soft to hard X-ray channels. Its cartoon representation is found throughout textbooks on solar and plasma astrophysics and guides interpretations of unresolved energetic flaring events on other stars, accretion disks, and jets. To date, a fully self-consistent model that reproduces the standard scenario in all its facets is lacking, since this requires the combination of a large-scale, multidimensional magnetohydrodynamic (MHD) plasma description with a realistic fast electron treatment. Here we demonstrate such a novel combination, where MHD combines with an analytic fast electron model, adjusted to handle time-evolving, reconnecting magnetic fields and particle trapping. This allows us to study (1) the role of fast electron deposition in the triggering of chromospheric evaporation flows, (2) the physical mechanisms that generate various hard X-ray sources at chromospheric footpoints or looptops, and (3) the relationship between soft X-ray and hard X-ray fluxes throughout the entire flare loop evolution. For the first time, this self-consistent solar flare model demonstrates the observationally suggested relationship between flux swept out by the hard X-ray footpoint regions and the actual reconnection rate at the X-point, which is a major unknown in flaring scenarios. We also demonstrate that a looptop hard X-ray source can result from fast electron trapping.

Keywords: Solar flares, X-ray sources
Gaussbock: Fast Parallel-iterative Cosmological Parameter Estimation with Bayesian Nonparametrics. We present and apply Gaussbock, a new embarrassingly parallel iterative algorithm for cosmological parameter estimation designed for an era of cheap parallel-computing resources. Gaussbock uses Bayesian nonparametrics and truncated importance sampling to accurately draw samples from posterior distributions with an orders-of-magnitude speed-up in wall time over alternative methods. Contemporary problems in this area often suffer from both increased computational costs due to high-dimensional parameter spaces and consequent excessive time requirements, as well as the need to fine-tune proposal distributions or sampling parameters. Gaussbock is designed specifically with these issues in mind. We explore and validate the performance and convergence of the algorithm on a fast approximation to the Dark Energy Survey Year 1 (DES Y1) posterior, finding reasonable scaling behavior with the number of parameters. We then test on the full DES Y1 posterior using large-scale supercomputing facilities and recover reasonable agreement with previous chains, although the algorithm can underestimate the tails of poorly constrained parameters. Additionally, we discuss and demonstrate how Gaussbock recovers complex posterior shapes very well at lower dimensions, but faces challenges to perform well on such distributions in higher dimensions. In addition, we provide the community with a user-friendly software tool for accelerated cosmological parameter estimation based on the methodology described in this paper.

Keywords: Astronomy data analysis, Astrostatistics, Cosmological parameters
Inferences About the Magnetic Field Structure of a CME with Both In Situ and Faraday Rotation Constraints. On 2012 August 2, two coronal mass ejections (CMEs; CME-1 and CME-2) erupted from the west limb of the Sun as viewed from Earth, and were observed in images from the white-light coronagraphs on the SOlar and Heliospheric Observatory and Solar TErrestrial RElations Observatory (STEREO) spacecraft. These events were also observed by the Very Large Array (VLA), which was monitoring the Sun at radio wavelengths, allowing time-dependent Faraday rotation observations to be made of both events. We use the white-light imaging and radio data to model the 3D field geometry of both CMEs, assuming a magnetic flux rope geometry. For CME-2, we also consider 1 au in situ field measurements in the analysis, as this CME hits STEREO-A on August 6, making this the first CME with observational constraints from stereoscopic coronal imaging, radio Faraday rotation, and in situ plasma measurements combined. The imaging and in situ observations of CME-2 provide two clear predictions for the radio data: VLA should observe positive rotation measures (RMs) when the radio line of sight first encounters the CME, and the sign should reverse to negative within two hours. The initial positive RMs are in fact observed. The expected sign reversal is not, but the VLA data unfortunately end too soon to be sure of the significance of this discrepancy. We interpret an RM increase prior to the expected occultation time of the CME as a signature of a sheath region of deflected field ahead of the CME itself.

Keywords: Interplanetary medium, Solar coronal mass ejections
Kinematic Structure of the Galactic Center S Cluster. We present a detailed analysis of the kinematics of 112 stars that mostly comprise the high-velocity S cluster and orbit the supermassive black hole Sgr A* at the center of the Milky Way. For 39 of them, orbital elements are known; for the remainder, we know proper motions. The distribution of the inclinations and the proper motion flight directions deviate significantly from a uniform distribution, which one expects if the orientation of the orbits are random. Across the central arcseconds, the S-cluster stars are arranged in two almost edge-on disks that are located at a position angle approximately ±45° with respect to the Galactic plane. The angular momentum vectors for stars in each disk point in both directions, I.e., the stars in a given disk rotate in opposite ways. The poles of this structure are located only about 25° from the line of sight. This structure may be the result of a resonance process that started with the formation of the young B-dwarf stars in the cluster about 6 Myr ago. Alternatively, it indicated the presence of a disturber at a distance from the center comparable to the distance of the compact stellar association IRS 13.

Keywords: Galactic center, Stellar dynamics, Black holes, Star clusters
Distinct Accretion Modes of Cygnus X-1 Revealed from Hard X-Rays. Thanks to recurrent observations of the black hole binary Cyg X-1 carried out over 15 years the INTEGRAL satellite has collected the largest data set in the hard X-ray band for this source. We have analyzed these data, complemented by data collected by other X-ray satellites and radio flux at 15 GHz. To characterize the spectral and variability properties of the system we have examined parameters such as the hard X-ray flux, photon index, and fractional variability. Our main result is that the 2D distribution of the photon index and flux determined for the 22-100 keV band forms six clusters. This result, interpreted within the Comptonization scenario as the dominant process responsible for the hard X-ray emission, leads to a conclusion that the hot plasma in Cyg X-1 takes the form of six specific geometries. The distinct character of each of these plasma states is reinforced by their different X-ray and radio variability patterns. In particular, the hardest and softest plasma states show no short-term flux-photon index correlation typical for the four other states, implying a lack of interaction between the plasma and accretion disk. The system evolves between these two extreme states, with the spectral slope regulated by a variable cooling of the plasma by the disk photons.

Keywords: X-ray binary stars, High mass x-ray binary stars