Sazuna/UAT_keywords huggingface dataset:
Hydrogen Burning of <SUP>29</SUP>Si and Its Impact on Presolar Stardust Grains from Classical Novae. Presolar stardust grains found in primitive meteorites are believed to retain the isotopic composition of stellar outflows at the time of grain condensation. Therefore, laboratory measurements of their isotopic ratios represent sensitive probes for investigating open questions related to stellar evolution, stellar explosions, nucleosynthesis, mixing mechanisms, dust formation, and galactic chemical evolution. For a few selected presolar grains, classical novae have been discussed as a potential source. For SiC, silicate, and graphite presolar grains, the association is based on the observation of small N(12C)/N(13C) and N(14N)/N(15N) number abundance ratios compared to solar values, and abundance excesses in 30Si relative to 29Si, as previously predicted by models of classical novae. We report on a direct measurement of the 29Si(p,γ)30P reaction, which strongly impacts simulated δ 29Si values from classical novae. Our new experimental 29Si(p,γ)30P thermonuclear reaction rate differs from previous results by up to 50% in the classical nova temperature range (T = 100-400 MK), while the rate uncertainty is reduced by up to a factor of 3. Using our new reaction rate in Monte Carlo reaction network and hydrodynamic simulations of classical novae, we estimate δ 29Si values with much reduced uncertainties. Our results establish δ 29Si values measured in presolar grains as a sensitive probe for assessing their classical nova paternity. We also demonstrate that δ 30Si values from nova simulations are currently not a useful diagnostic tool unless the large uncertainty of the 30P(p,γ)31S reaction rate can be significantly reduced.

Keywords: Meteorites, Nuclear reaction cross sections, Explosive nucleosynthesis, Classical novae
Testing the Alfvén-wave Model of the Solar Wind with Interplanetary Scintillation. Understanding the mechanism(s) of solar wind acceleration is important in astrophysics and geophysics. A promising model of solar wind acceleration is known as the wave/turbulence-driven (WTD) model, in which Alfvén waves feed energy to the solar wind. In this study, we tested the WTD model with global measurements of wind speed from interplanetary scintillation (IPS) observations. For Carrington rotations in minimal and maximal activity phases, we selected field lines calculated by the potential-field source-surface method in high and midlatitudes and compared the simulated and observed wind velocities. The simulation was performed in a self-consistent manner by solving the magnetohydrodynamic equations from the photosphere to the solar wind. In high-latitude regions, the simulated solar wind velocity agrees better with the IPS observation than with the classical Wang-Sheeley empirical estimation, both in maximal and minimal activity phases. In midlatitude regions, the agreement worsens, possibly because of the inaccuracy of the WTD model and/or the magnetic-field extrapolation. Our results indicate that the high-latitude solar wind is likely to be driven by waves and turbulence and that the physics-based prediction of the solar wind velocity is highly feasible with an improved magnetic-field extrapolation.

Keywords: Alfven waves, Solar wind, Interplanetary physics, Magnetohydrodynamical simulations
Quantitative Evaluation of Coronal Magnetic Field Models Using Tomographic Reconstructions of Electron Density. We introduce a new quantitative approach for assessing the quality of coronal magnetic field models. The method compares the location of the magnetic neutral line at a specified height in the magnetic field model with the locations of localized density peaks in the coronal electron density, as measured using coronal rotational tomography. This approach is flexible to the presence of pseudostreamers in the coronal magnetic field, as well as folds in the streamer belt. We present an example application during mid-2010 when the white-light streamer-belt structure is complex and the emergence of a large active region on the far side of the Sun presents a challenge for modeling the coronal magnetic structure.

Keywords: Model selection, Coronagraphic imaging, Solar corona
Velocity Anisotropy in Self-gravitating Molecular Clouds. II. Observation. The view on velocity structures in molecular clouds and their relationship with magnetic fields (B field) has evolved during the past decade from almost no correlation to highly parallel. Our numerical simulations suggest a more nuanced picture: Depending on whether the self-gravity is dynamically dominant, the velocity field can be governed by either contraction (at high densities) or turbulence (at low densities), and their anisotropies will tend to be either perpendicular or parallel, respectively, to the B fields. High-density regions are always embedded in the low-density fore/background, so the velocity behaviors from lines of sight (LOSs) with high column densities will be a mixture of orthogonal anisotropies, which can be hard to interpret and necessitates zooming in onto certain LOS scales to better characterize localized behaviors. We tested and confirmed the above prediction with CO observations of the Taurus molecular cloud.

Keywords: Interstellar magnetic fields, Star forming regions, Molecular clouds
Evidence of Magnetic Reconnection with Multiple X Lines and Flux Ropes in Thin Magnetotail Currents Observed by the MMS Spacecraft: Results of Grad-Shafranov Reconstruction. There is some observational evidence for the existence of multiple X line magnetic reconnection (MR) in various planetary magnetotails but the overall observationally based MR topology in two or three dimensions is still not available. This study reports the first 2D structures of MR with multiple X lines and magnetic islands observed by the Magnetospheric Multiscale (MMS) spacecraft in the Earth's magnetotail based on the Grad-Shafranov (GS) reconstruction model with temperature anisotropy. The tearing mode geometry is revealed within the spatial domain of 3800 km × 800 km with multiple X lines and magnetic islands on the spatial scale of the sub-ion inertial length or a few times the electron gyroradius. The MR event is seen by all four MMS spacecraft but the magnetic islands are caught only by the MMS3 spacecraft, and exhibit large firehose-type temperature anisotropy. The GS reconstructed maps based on the MMS1, 2, and 4 show a single X line and partial ion-scale magnetic islands with a smaller degree of temperature anisotropy. The reconstruction results remain the same for various energy closures, and the firehose-type anisotropy is found to yield smaller magnetic islands than the isotropic cases, which is opposite to the previous findings for MR events with mirror-type temperature anisotropy.

Keywords: Planetary magnetospheres, Space plasmas, Plasma astrophysics, Plasma physics
Optical and Near-infrared Excesses are Correlated in T Tauri Stars. Accretion is one of the defining characteristics of classical T Tauri stars, fueled by the presence of a circumstellar disk comprised of dust and gas. Accretion produces a UV and optical excess, while re-radiated emission at the inner edge of the dust component of the disk produces a near-infrared (NIR) excess. The interplay between stars and their disks helps regulate protoplanetary disk evolution and dispersal, which is key to a full understanding of planet formation. To investigate the relations between NIR excess and optical excess in both single and binary stars, we used an archival sample of spectroscopically characterized members of the Taurus star-forming region (τ ~ 1-2 Myr) with measured luminosities, spectral types, and optical veiling. We combined the archival sample with the Two Micron All Sky Survey and Wide-field Infrared Survey Explorer NIR photometry and high-resolution imaging surveys. We found that NIR and optical excesses are correlated in multiple NIR photometric bands, suggesting that they are closely related, likely because more massive disks have higher inner dust disk walls and are also associated with higher accretion rates. We also found that multiplicity has no impact on accretion or inner disk properties in a sample with a wide range of separations, but the sample was too small to specifically investigate close binaries, where the effects of multiplicity on disk properties should be most significant.

Keywords: T Tauri stars, Young stellar objects, Protoplanetary disks, Stellar accretion, Circumstellar disks
Photometric Analysis of the OGLE Heartbeat Stars. We present an analysis of 991 heartbeat stars (HBSs) from the OGLE Collection of Variable Stars. The sample consists of 512 objects located toward the Galactic bulge, 439 in the Large Magellanic Cloud, and 40 in the Small Magellanic Cloud. We model the I-band OGLE light curves using an analytical model of flux variations reflecting tidal deformations between stars. We present distributions of the model parameters that include the eccentricity, orbital inclination, and argument of the periastron but also the period-amplitude diagrams. On the Hertzsprung-Russell diagram, our HBS sample forms two separate groups of different evolutionary status. The first group, including about 90 systems with short orbital periods (P ≲ 50 days), consists of an early-type primary star lying on (or close to) the main sequence. The second group, including about 900 systems with long orbital periods (P ≳ 100 days), contains a red giant (RG). The position of the RG HBSs on the period-luminosity diagram strongly indicates their binary nature. They appear to be a natural extension of confirmed binary systems that include the OGLE ellipsoidal and long secondary period variables. We also present a time-series analysis leading to detection of tidally excited oscillations (TEOs). We identify such pulsations in about 5% of stars in the sample with a total of 78 different modes. This first relatively large homogeneous sample of TEOs allowed us to construct a diagram revealing the correlation between the TEO's orbital harmonic number and the eccentricity of the host binary system.

Keywords: Periodic variable stars, Astronomy data modeling, Tidal distortion, Binary stars, Elliptical orbits, Galactic bulge, Time domain astronomy, Stellar oscillations, Magellanic Clouds, Astronomical simulations
Charge States, Helium Abundance, and FIP Bias of the Interplanetary CMEs Classified by Flares and Hot Channels. Identifying the material source of coronal mass ejections (CMEs) is crucial for understanding the generation mechanisms of CMEs. The composition parameters of interplanetary coronal mass ejections (ICMEs) associated with different activities on the Sun may be diverse, as the materials come from distinct regions or are generated by different processes. We classified ICMEs into three types by associated activities on the Sun, with (T1) and without (T3) flares and hot channels, and only associated with flares (T2). The composition parameters of each type of ICMEs were analyzed. We found that all CMEs with hot channels are accompanied by flares, and strong flares are all associated with hot channels in our database. The average length of the filaments in T1 cases are much shorter than those in T3 cases. The average charge states of iron (Q Fe) and helium abundance (A He) for T3 ICMEs are less than 12% and 7%, respectively. The Q Fe and A He for T1 ICMEs present clear bimodal distributions with the minimum between two peaks at 12% and 7%, respectively. Nearly two-thirds of the hot plasma (with higher Q Fe) inside ICMEs is associated with higher A He. The Q Fe and A He are both positively correlated with the flare intensities. The A He and filament scales are not explicitly linked to each other. The statistical results demonstrate that the material contribution of the filaments to ICMEs is low and more than half of the hot materials inside ICMEs originate from the chromosphere in our database. We suggest that they are heated by the chromospheric evaporation process at the hot channel (flux rope) footpoint regions before and/or during the flaring process.

Keywords: Solar abundances, Solar flares, Solar coronal mass ejections
Electromagnetic Signatures from Supermassive Binary Black Holes Approaching Merger. We present fully relativistic predictions for the electromagnetic emission produced by accretion disks surrounding spinning and nonspinning supermassive binary black holes on the verge of merging. We use the code Bothros to post-process data from 3D general relativistic magnetohydrodynamic simulations via ray-tracing calculations. These simulations model the dynamics of a circumbinary disk and the mini-disks that form around two equal-mass black holes orbiting each other at an initial separation of 20 gravitational radii, and evolve the system for more than 10 orbits in the inspiral regime. We model the emission as the sum of thermal blackbody radiation emitted by an optically thick accretion disk and a power-law spectrum extending to hard X-rays emitted by a hot optically thin corona. We generate time-dependent spectra, images, and light curves at various frequencies to investigate intrinsic periodic signals in the emission, as well as the effects of the black hole spin. We find that prograde black hole spin makes mini-disks brighter since the smaller innermost stable circular orbit angular momentum demands more dissipation before matter plunges to the horizon. However, compared to mini-disks in larger separation binaries with spinning black holes, our mini-disks are less luminous: unlike those systems, their mass accretion rate is lower than in the circumbinary disk, and they radiate with lower efficiency because their inflow times are shorter. Compared to a single black hole system matched in mass and accretion rate, these binaries have spectra noticeably weaker and softer in the UV. Finally, we discuss the implications of our findings for the potential observability of these systems.

Keywords: Accretion, Spacetime metric, High energy astrophysics, Active galactic nuclei, General relativity, Compact objects, Astrophysical black holes
Unveiling the Nature of SN 2011fh: A Young and Massive Star Gives Rise to a Luminous SN 2009ip-like Event. In recent years, many Type IIn supernovae have been found to share striking similarities with the peculiar SN 2009ip, whose true nature is still under debate. Here, we present 10 yr of observations of SN 2011fh, an interacting transient with spectroscopic and photometric similarities to SN 2009ip. SN 2011fh had an M  r  ~ -16 mag brightening event, followed by a brighter M  r  ~ -18 mag luminous outburst in 2011 August. The spectra of SN 2011fh are dominated by narrow to intermediate Balmer emission lines throughout its evolution, with P Cygni profiles indicating fast-moving material at ~6400 km s-1. HST/WFC3 observations from 2016 October revealed a bright source with M F814W ≍ -13.3 mag, indicating that we are seeing the ongoing interaction of the ejecta with the circumstellar material or that the star might be going through an eruptive phase five years after the luminous outburst of 2011. Using HST photometry of the stellar cluster around SN 2011fh, we estimated an age of ~4.5 Myr for the progenitor, which implies a stellar mass of ~60 M ☉, using single-star evolution models, or a mass range of 35-80 M ☉, considering a binary system. We also show that the progenitor of SN 2011fh exceeded the classical Eddington limit by a large factor in the months preceding the luminous outburst of 2011, suggesting strong super-Eddington winds as a possible mechanism for the observed mass loss. These findings favor an energetic outburst in a young and massive star, possibly a luminous blue variable.

Keywords: Transient sources, Massive stars, Supernovae, Stellar mass loss
Dependence of Pulsation Mode of Cepheids on Metallicity. The Cepheid variables in the Small Magellanic Cloud (SMC), the Large Magellanic Cloud (LMC), the Milky Way, M33, and M31 are used to examine the dependence of pulsation mode on metallicity, which was previously found in red supergiants. The initial samples of Cepheids are collected from the Cepheid catalogs identified from the Optical Gravitational Lensing Experiment, PS1, DIRECT, Wide-field Infrared Survey Explorer, and Zwicky Transient Facility surveys. The contaminants are removed with the help of the Gaia/EDR3 astrometric information for extra galaxies or by comparing the geometric distance and the distance from the P-L relation for the Milky Way. The division of fundamental (FU) and first-overtone (1O) modes is refined according to the gap between the two modes in the P-L diagram of the objects in each galaxy. The ratio of FU/(FU+1O) is found to be 0.59, 0.60, 0.69, 0.83, and 0.85 for the SMC, the LMC, the Milky Way, M33, and M31, respectively, in order of metallicity, which confirms that the pulsation mode depends on metallicity in the way that the ratio of FU/(FU+1O) increases with metallicity. This dependence is not changed if the incompleteness of the samples is taken into account.

Keywords: Cepheid variable stars, Metallicity, Pulsation modes
Tidal Evolution and Diffusive Growth During High-eccentricity Planet Migration: Revisiting the Eccentricity Distribution of Hot Jupiters. High-eccentricity tidal migration is a potential formation channel for hot Jupiters. During this process, the planetary f-mode may experience a phase of diffusive growth, allowing its energy to quickly build up to large values. In Yu et al., we demonstrated that nonlinear mode interactions between a parent f-mode and daughter f- and p-modes expand the parameter space over which the diffusive growth of the parent is triggered. We extend that study by incorporating (1) the angular momentum transfer between the orbit and the mode, and consequently the evolution of the pericenter distance; (2) a prescription to regulate the nonlinear frequency shift at high parent mode energies; and (3) dissipation of the parent's energy due to both turbulent convective damping of the daughter modes and strongly nonlinear wave-breaking events. The new ingredients allow us to follow the coupled evolution of the mode and orbit over ≳104 yr, covering the diffusive evolution from its onset to its termination. We find that the semimajor axis shrinks by a factor of nearly 10 over 104 yr, corresponding to a tidal quality factor ${ \mathcal Q }\sim 10$ . The f-mode's diffusive growth terminates while the eccentricity is still high, at around e = 0.8-0.95. Using these results, we revisit the eccentricity distribution of proto-hot Jupiters. We estimate that less than 1 proto-HJ with eccentricity &gt;0.9 should be expected in Kepler's data once the diffusive regime is accounted for, explaining the observed paucity of this population.

Keywords: Exoplanet migration, Hot Jupiters, Hydrodynamics, Exoplanets, Exoplanet tides
A Multimission Method for the Reconstruction of Gamma-ray Events on Silicon Tracker Pair Telescopes. γ-ray astronomy in the energy range from MeV to GeV can provide a unique detection window for γ-ray bursts and other transient sources, fundamental information on particle acceleration mechanisms, MeV-blazar population studies up to z ~ 4.5, and a full overview of line emission from cosmic-ray interaction. Silicon-based pair tracking telescopes rely on γ-ray conversion into an electron-positron pair and its tracking using a stack of silicon strips. The method presented in this work is based on a Rauch-Tung-Striebel smoother. Its internal Kalman filter enables keeping multiple hypotheses about particle tracks and implementing statistically meaningful measurement selection among hits on different planes of the tracker. The algorithm can be easily configured to work with different tracker geometries and mass models. It can be used for the exploitation of data from past and current γ-ray missions as well as to assess the performances of new pair-tracking telescopes. The proposed method has been validated on Astrorivelatore Gamma a Immagini Leggero data and then used to investigate the performances of both e-ASTROGAM and All-Sky-ASTROGAM telescopes. The algorithm efficiency and its accuracy in estimating both the photon direction and energy were evaluated on γ-ray events simulated at different energies in the range between 30 MeV and 3 GeV. The point-spread function of each tracker was then compared with its angular resolution limit showing both the expected performances of the instrument and the margin of improvement that could be obtained by optimizing the reconstruction method.

Keywords: Gamma-ray detectors, Bayesian statistics, Algorithms, Gamma-ray telescopes
The Number of Possible CETIs within Our Galaxy and the Communication Probability among These CETIs. As the only known intelligent civilization, human beings are always curious about the existence of other communicating extraterrestrial intelligent civilizations (CETIs). Based on the latest astrophysical information, we carry out Monte Carlo simulations to estimate the number of possible CETIs within our Galaxy and the communication probability among them. Two poorly known parameters have a great impact on the results. One is the probability of life appearing on terrestrial planets and eventually evolving into a CETI (f  c ), and the other determines at what stage of their host star's evolution CETIs would be born (F). In order to ensure the completeness of the simulation, we consider a variety of combinations of f  c  and F. Our results indicate that for optimistic situations (e.g., F = 25% and f  c  = 0.1%), there could be ${\mathrm{42,777}}_{-369}^{+267}$ CETIs and they need to survive for ${3}_{-2}^{+17}$ yr ( ${2000}_{-1400}^{+2000}$ yr) to achieve one-way communication (two-way communication). In this case, human beings need to survive ${0.3}_{-0.298}^{+0.6}$ Myr to receive one alien signal. For pessimistic situations (e.g., F = 75% and f  c  = 0.001%), only ${111}_{-17}^{+28}$ CETIs could be born and they need to survive for ${0.8}_{-0.796}^{+1.2}$ Myr ( ${0.9}_{-0.88}^{+4.1}$ Myr) to achieve one-way communication (two-way communication). In this case, human beings need to survive ${50}_{-49.6}^{+250}$ Myr to receive one signal from other CETIs. Our results may quantitatively explain why we have not detected any alien signals so far. The uncertainty of the results has been discussed in detail and would be alleviated with the further improvement of our astronomical observation ability in the future.

Keywords: Astrobiology
A Search for Correlations between Turbulence and Star Formation in THINGS Galaxies. The spatial range for feedback from star formation varies from molecular cloud disruption on parsec scales to supershells and disk blowout on kiloparsec scales. The relative amounts of energy and momentum given to these scales are important for understanding the termination of star formation in any one region and the origin of interstellar turbulence and disk stability in galaxies as a whole. Here, we measure, for 11 THINGS galaxies, the excess kinetic energy, velocity dispersion, and surface density of H I gas associated with regions of excess star formation, where the excess is determined from the difference between the observed local value and the azimuthal average. We find small decreases in the excess kinetic energy and velocity dispersion in regions of excess star formation rate density, suggesting that most of the feedback energy does not go into local H I motion. Most likely, it disrupts molecular clouds and dissipates rapidly at high gas density. Some could also be distributed over larger regions, filling in spaces between the peaks of star formation and contributing to other energy sources from self-gravity and spiral arm shocks.

Keywords: Star forming regions, Stellar feedback, Interstellar atomic gas