Sazuna/UAT_keywords huggingface dataset:
On Stellar Evolution in a Neutrino Hertzsprung-Russell Diagram. We explore the evolution of a select grid of solar metallicity stellar models from their pre-main-sequence phase to near their final fates in a neutrino Hertzsprung-Russell diagram, where the neutrino luminosity replaces the traditional photon luminosity. Using a calibrated MESA solar model for the solar neutrino luminosity ( ${L}_{\nu ,\odot }=0.02398$ · ${L}_{\gamma ,\odot }=9.1795$ × 1031 erg s-1) as a normalization, we identify ≃0.3 MeV electron neutrino emission from helium burning during the helium flash (peak ${L}_{\nu }/{L}_{\nu ,\odot }\simeq {10}^{4}$ , flux ${{\rm{\Phi }}}_{\nu ,\mathrm{He}\mathrm{flash}}\simeq 170$ (10 pc/d)2 cm-2 s-1 for a star located at a distance of d parsec, timescale ≃3 days) and the thermal pulse (peak ${L}_{\nu }/{L}_{\nu ,\odot }\simeq {10}^{9}$ , flux ${{\rm{\Phi }}}_{\nu ,\mathrm{TP}}\simeq 1.7$ × 107 (10 pc/d)2 cm-2 s-1, timescale ≃0.1 yr) phases of evolution in low-mass stars as potential probes for stellar neutrino astronomy. We also delineate the contribution of neutrinos from nuclear reactions and thermal processes to the total neutrino loss along the stellar tracks in a neutrino Hertzsprung-Russell diagram. We find, broadly but with exceptions, that neutrinos from nuclear reactions dominate whenever hydrogen and helium burn, and that neutrinos from thermal processes dominate otherwise.

Keywords: Neutrino astronomy, Stellar physics, Hertzsprung Russell diagram, Stellar evolutionary tracks, Stellar evolution
The Importance of Star Formation Intensity in Lyα Escape from Green Pea Galaxies and Lyman Break Galaxy Analogs. We have studied ultraviolet images of 40 Green Pea galaxies and 15 local Lyman Break Galaxy Analogs to understand the relation between Lyα photon escape and central UV photometric properties. We measured star-formation intensity (SFI; star formation rate per unit area) from the central 250 pc region ( ${S}_{250\mathrm{pc}}$ ) using Cosmic Origins Spectrograph near-ultraviolet images from the Hubble Space Telescope. The measured ${S}_{250\mathrm{pc}}$ of our sample Green Peas ranges from 2.3-46 M⊙ yr-1 kpc-2, with a geometric mean of 15 M⊙ yr-1 kpc-2 and a standard deviation of 0.266 dex, forming a relatively narrow distribution. The Lyman Break Galaxy Analogs show a similarly narrow distribution of ${S}_{250\mathrm{pc}}$ (0.271 dex), though with a larger mean of 28 M⊙ yr-1 kpc-2. We show that while the Lyα equivalent width (EW(Lyα)) and the Lyα escape fraction ( ${f}_{\mathrm{esc}}^{\mathrm{Ly}\alpha }$ ) are not significantly correlated with the central SFI ( ${S}_{250\mathrm{pc}}$ ), both are positively correlated with the ratio of surface brightness to galaxy stellar mass (S250 pc/Mstar), with correlation coefficients (p-values) of 0.702 (1 × 10-8) and 0.529 (5 × 10-4) with EW(Lyα) and ${f}_{\mathrm{esc}}^{\mathrm{Ly}\alpha }$ , respectively. These correlations suggest a scenario where intense central star formation can drive a galactic wind in galaxies with relatively shallow gravitational potential wells, thus clearing channels for the escape of Lyα photons.

Keywords: Starburst galaxies, Galaxy formation, Compact galaxies, Galaxy structure, Star formation, Galaxy evolution, Reionization
Mass Functions of Giant Molecular Clouds and Young Star Clusters in Six Nearby Galaxies. We compare the mass functions of young star clusters (ages ≤ 10 Myr) and giant molecular clouds (GMCs) in six galaxies that cover a large range in mass, metallicity, and star formation rate (LMC, M83, M51, NGC 3627, the Antennae, and NGC 3256). We perform maximum-likelihood fits of the Schechter function, $\psi (M)\,={dN}/{dM}\propto {M}^{\beta }\exp (-M/{M}_{\ast })$ , to both populations. We find that most of the GMC and cluster mass functions in our sample are consistent with a pure power-law distribution ( ${M}_{* }\to \infty $ ). M51 is the only galaxy that shows some evidence for an upper cutoff (M*) in both populations. Therefore, physical upper mass cutoffs in populations of both GMCs and clusters may be the exception rather than the rule. When we perform power-law fits, we find a relatively small range of indices βPL = -2.3 ± 0.3 for our GMC sample and βPL = -2.0 ± 0.3 for the cluster sample. This result, that ${\beta }_{\mathrm{Clusters}}\approx {\beta }_{\mathrm{GMC}}\approx -2$ , is consistent with theoretical predictions for cluster formation and suggests that the star formation efficiency is largely independent of mass in the GMCs.

Keywords: Giant molecular clouds, Young star clusters, Star formation
A Statistical Study of the Plasma and Composition Distribution inside Magnetic Clouds: 1998-2011. A comprehensive analysis of plasma and composition characteristics inside magnetic clouds (MCs) observed by the Advanced Composition Explorer spacecraft from 1998 February to 2011 August is presented. The results show that MCs have specific interior structures, and MCs of different speeds show differences in composition and structure. Compared with the slow MCs, fast MCs have enhanced mean charge states of iron, oxygen, silicon, magnesium, ${{\rm{O}}}^{7+}/{{\rm{O}}}^{6+}$ , ${{\rm{C}}}^{6+}/{{\rm{C}}}^{5+}$ , ${{\rm{C}}}^{6+}/{{\rm{C}}}^{4+}$ , and ${\mathrm{Fe}}^{\geqslant 16+}/{\mathrm{Fe}}_{\mathrm{total}}$ values. For ionic species in fast MCs, a higher atomic number represents a greater enhancement of mean charge state than slow MCs. We also find that both the fast and slow MCs display bimodal structure distribution in the mean iron charge state ( $\langle Q\rangle \mathrm{Fe}$ ), which suggests that the existence of flux rope prior to the eruption is common. Furthermore, the $\langle Q\rangle \mathrm{Fe}$ , ${\mathrm{Fe}}^{\geqslant 16+}/{\mathrm{Fe}}_{\mathrm{total}}$ , and ${{\rm{O}}}^{7+}/{{\rm{O}}}^{6+}$ ratio distribution inside fast MCs have the feature that the posterior peak is higher than the anterior one. This result agrees with the "standard model" for coronal mass ejection/flares, by which magnetic reconnection occurs beneath the flux rope, thereby ionizing the ions of the posterior part of the flux rope sufficiently by high-energy electron collisions or by direct heating in the reconnection region.

Keywords: Solar flares, Solar wind, Solar physics, Solar filaments, Solar coronal mass ejections, Solar filament eruptions, Solar storm, Interplanetary physics
Pointing Chandra toward the Extreme Ultraviolet Fluxes of Very Low Mass Stars. The X-ray and EUV emission of stars plays a key role in the loss and evolution of the atmospheres of their planets. The coronae of dwarf stars later than M6 appear to behave differently from those of earlier spectral types and are more X-ray dim and radio bright. Too faint to have been observed by the Extreme Ultraviolet Explorer, their EUV behavior is currently highly uncertain. We have devised a method to use the Chandra X-ray Observatory High Resolution Camera to provide a measure of EUV emission in the 50-170 Å range and applied it to the M6.5 dwarf LHS 248 in a pilot 10 ks exposure. Analysis with model spectra using simple, idealized coronal emission measure distributions inspired by the Chandra Low Energy Transmission Grating spectra of the M5.5 dwarf Proxima Cen and results from the literature finds the greatest consistency with a very shallow emission measure distribution slope, DEM ∝ T3/2 or shallower, in the range log T = 5.5-6.5, although this could be an artifact of systematic errors. Instead, cooler, more solar-like differential emission measures (DEMs) with a wide range of slopes were able to match the observations. Within the limitations of systematic errors, model spectra constrained by this method can provide accurate (within a factor of 2-4) synthesis and extrapolation of EUV spectra for wavelengths &lt;400-500 Å. At longer wavelengths, models are uncertain by an order of magnitude or more and depend on the details of the emission measure distribution at temperatures log T &lt; 5.5. The method is sensitive to the possible incompleteness of plasma radiative loss models in the 30-170 Å range for which reexamination would be warranted.

Keywords: M dwarf stars, Late-type stars, Solar extreme ultraviolet emission, Stellar activity, X-ray stars, Stellar coronae, Exoplanet atmospheres
Modeling Rotational Disruption of Grains and Microwave Emission from Spinning Dust in AGB Envelopes. Radio observations of some asymptotic giant branch (AGB) star envelopes show excess emission at frequencies below 100 GHz that cannot be explained by thermal dust emission (hereafter anomalous microwave emission (AME)). Moreover, AGB envelopes are a common place where gas molecules condense to form nanoparticles (e.g., polycyclic aromatic hydrocarbons) and large grains. In this paper, we study whether electric dipole emission from rapidly spinning nanoparticles can reproduce the AME observed toward AGB stars. To properly model the size distribution of nanoparticles in the AGB envelope, we take into account both the increase of nanoparticles due to rotational disruption of large grains spun up by radiative torques and the decrease of the smallest nanoparticles due to rotational disruption driven by stochastic gas collisions. We then perform detailed modeling of microwave emission from rapidly spinning nanoparticles from both C-rich and O-rich AGB envelopes using the grain-size distribution constrained by rotational disruption. We find that spinning dust emission is dominant over thermal dust emission at frequencies below 100 GHz. We attempt to fit the observational data of AME using our spinning dust model and demonstrate that spinning dust can reproduce the observed AME in six AGB stars. Finally, we discuss how microwave emission from spinning dust in AGB envelopes could be observed with high-resolution upcoming radio telescopes such the Next Generation Very Large Array and Atacama Large Millimeter/submillimeter Array Band 1. This would be a major leap for understanding AGB envelopes' formation, evolution, and internal structures of dust. Observations would help to distinguish the carrier of AME via comparisons of C-rich and O-rich stars, because polycyclic aromatic hydrocarbons (PAHs) are formed in C-rich AGB stars, while silicates are formed in O-rich stars.

Keywords: Circumstellar envelopes, Interstellar dust extinction, Asymptotic giant branch stars, Interstellar extinction, Radio continuum emission
The Formation History of Subhalos and the Evolution of Satellite Galaxies. Satellites constitute an important fraction of the overall galaxy population and are believed to form in dark matter subhalos. Here we use the cosmological hydrodynamic simulation TNG100 to investigate how the formation histories of subhalos affect the properties and evolution of their host galaxies. We use a scaled formation time ( ${a}_{\mathrm{nf}}$ ) to characterize the mass assembly histories of the subhalos before they are accreted by massive host halos. We find that satellite galaxies in young subhalos (low ${a}_{\mathrm{nf}}$ ) are less massive and more gas-rich and have stronger star formation and a higher fraction of ex situ stellar mass than satellites in old subhalos (high ${a}_{\mathrm{nf}}$ ). Furthermore, these low- ${a}_{\mathrm{nf}}$ satellites require longer timescales to be quenched as a population than the high- ${a}_{\mathrm{nf}}$ counterparts. We find very different merger histories between satellites in fast-accretion (FA, ${a}_{\mathrm{nf}}\lt 1.3$ ) and slow-accretion (SA, ${a}_{\mathrm{nf}}\gt 1.3$ ) subhalos. For FA satellites the galaxy merger frequency dramatically increases just after accretion, which enhances the star formation at accretion, whereas for SA satellites the mergers occur smoothly and continuously across the accretion time. Moreover, mergers with FA satellites happen mainly after accretion, while a contrary trend is found for SA satellites. Our results provide insight into the evolution and star formation quenching of the satellite population.

Keywords: Cosmology, Hydrodynamical simulations, Galaxy evolution
The Impact of Planetary Rotation Rate on the Reflectance and Thermal Emission Spectrum of Terrestrial Exoplanets around Sunlike Stars. Robust atmospheric and radiative transfer modeling will be required to properly interpret reflected-light and thermal emission spectra of terrestrial exoplanets. This will help break observational degeneracies between the numerous atmospheric, planetary, and stellar factors that drive planetary climate. Here, we simulate the climates of earthlike worlds around the Sun with increasingly slow rotation periods, from earthlike to fully Sun-synchronous, using the ROCKE-3D general circulation model. We then provide these results as input to the Spectral Planet Model, which employs the Spectral Mapping Atmospheric Radiative Transfer model to simulate the spectra of a planet as it would be observed from a future space-based telescope. We find that the primary observable effects of slowing planetary rotation rate are the altered cloud distributions, altitudes, and opacities that subsequently drive many changes to the spectra by altering the absorption band depths of biologically relevant gas species (e.g., ${{\rm{H}}}_{2}{\rm{O}}$ , ${{\rm{O}}}_{2}$ , and ${{\rm{O}}}_{3}$ ). We also identify a potentially diagnostic feature of synchronously rotating worlds in mid-infrared ${{\rm{H}}}_{2}{\rm{O}}$ absorption/emission lines.

Keywords: Exoplanet detection methods, Exoplanet atmospheric variability, Planetary atmospheres, Exoplanet atmospheres
How Does Magnetic Reconnection Drive the Early-stage Evolution of Coronal Mass Ejections?. Theoretically, coronal mass ejection (CME) kinematics are related to magnetic reconnection processes in the solar corona. However, the current quantitative understanding of this relationship is based on the analysis of only a handful of events. Here we report a statistical study of 60 CME-flare events from 2010 August to 2013 December. We investigate kinematic properties of CMEs and magnetic reconnection in the low corona during the early phase of the eruptions, by combining limb observations from STEREO with simultaneous on-disk views from SDO. For a subset of 42 events with reconnection rate evaluated by the magnetic fluxes swept by the flare ribbons on the solar disk observed from SDO, we find a strong correlation between the peak CME acceleration and the peak reconnection rate. Also, the maximum velocities of relatively fast CMEs (≳600 km s-1) are positively correlated with the reconnection flux, but no such correlation is found for slow CMEs. A time-lagged correlation analysis suggests that the distribution of the time lag of CME acceleration relative to reconnection rate exhibits three peaks, approximately 10 minutes apart, and on average, acceleration-led events have smaller reconnection rates. We further compare the CME total mechanical energy with the estimated energy in the current sheet. The comparison suggests that, for small-flare events, reconnection in the current sheet alone is insufficient to fuel CMEs. Results from this study suggest that flare reconnection may dominate the acceleration of fast CMEs, but for events of slow CMEs and weak reconnection, other mechanisms may be more important.

Keywords: Coronagraphic imaging, Solar flares, Solar coronal mass ejections, Solar magnetic reconnection
2016 Outburst of H 1743-322: XMM-Newton and NuSTAR View. We report the detection of a type C quasi-periodic oscillation (QPO) along with an upper harmonic in the commensurate ratio of 1:2 in two observations of the low-mass black hole transient H 1743-322 jointly observed by XMM-Newton and NuSTAR during the 2016 outburst. We find that the QPO and the upper harmonic exhibit shifts in their centroid frequencies in the second observation with respect to the first one. The hardness intensity diagram implies that in contrast to the 2008 and 2014 failed outbursts, the 2016 outburst was a successful one. We also detect the presence of a broad iron Kα line at ∼6.5 keV and a reflection hump in the energy range 15-30 keV in both of the observations. Along with the shape of the power density spectra, the nature of the characteristic frequencies and the fractional rms amplitude of the timing features imply that the source stayed in the low/hard state during these observations. Moreover, the photon index and other spectral parameters also indicate the low/hard state behavior of the source. Unlike the soft lag detected in this source during the 2008 and 2014 failed outbursts, we observe hard time lags of 0.40 ± 0.15 s and 0.32 ± 0.07 s in the 0.07-0.4 Hz frequency range in the two observations during the 2016 outburst. The correlation between the photon index and the centroid frequency of the QPO is consistent with the previous results. Furthermore, the high value of the Comptonized fraction and the weak thermal component indicate that the QPO is being modulated by the Comptonization process.

Keywords: Low-mass x-ray binary stars, Stellar mass black holes, High energy astrophysics
SN 2019ein: New Insights into the Similarities and Diversity among High-velocity Type Ia Supernovae. We present optical observations of the Type Ia supernova (SN) 2019ein, starting two days after the estimated explosion date. The spectra and light curves show that SN 2019ein belongs to a high-velocity (HV) and broad-line group with a relatively rapid decline in the light curves (Δm15(B) = 1.36 ± 0.02 mag) and a short rise time (15.37 ± 0.55 days). The Si II λ6355 velocity, associated with a photospheric component but not with a detached high-velocity feature, reached ∼20,000 km s-1 12 days before the B-band maximum. The line velocity, however, decreased very rapidly and smoothly toward maximum light, to ∼13,000 km s-1, which is relatively low among HV SNe. This indicates that the speed of the spectral evolution of HV SNe Ia is correlated with not only the velocity at maximum light, but also the light-curve decline rate, as is the case for normal-velocity (NV) SNe Ia. Spectral synthesis modeling shows that the outermost layer at &gt;17,000 km s-1 is well described by an O-Ne-C burning layer extending to at least 25,000 km s-1, and there is no unburnt carbon below 30,000 km s-1; these properties are largely consistent with the delayed detonation scenario and are shared with the prototypical HV SN 2002bo despite the large difference in Δm15(B). This structure is strikingly different from that derived for the well-studied NV SN 2011fe. We suggest that the relation between the mass of 56Ni (or Δm15) and the extent of the O-Ne-C burning layer provides an important constraint on the explosion mechanism(s) of HV and NV SNe.

Keywords: Type Ia supernovae, Supernovae
Evidence of Particle Acceleration in the Superbubble 30 Doradus C with NuSTAR. We present evidence of diffuse, non-thermal X-ray emission from the superbubble 30 Doradus C (30 Dor C) using hard X-ray images and spectra from NuSTAR observations. For this analysis, we utilize data from a 200 ks targeted observation of 30 Dor C as well as 2.8 Ms of serendipitous off-axis observations from the monitoring of nearby SN 1987A. The complete shell of 30 Dor C is detected up to 20 keV, and the young supernova remnant MCSNR J0536-6913 in the southeast of 30 Dor C is not detected above 8 keV. Additionally, six point sources identified in previous Chandra and XMM-Newton investigations have hard X-ray emission coincident with their locations. Joint spectral fits to the NuSTAR and XMM-Newton spectra across the 30 Dor C shell confirm the non-thermal nature of the diffuse emission. Given the best-fit rolloff frequencies of the X-ray spectra, we find maximum electron energies of ≍70-110 TeV (assuming a B-field strength of 4 μG), suggesting 30 Dor C is accelerating particles. Particles are either accelerated via diffusive shock acceleration at locations where the shocks have not stalled behind the Hα shell, or cosmic-rays are accelerated through repeated acceleration of low-energy particles via turbulence and magnetohydrodynamic waves in the bubble's interior.

Keywords: X-ray astronomy, Shocks, Interstellar medium, Superbubbles
Time Dependence of the Flux of Helium Nuclei in Cosmic Rays Measured by the PAMELA Experiment between 2006 July and 2009 December. Precise time-dependent measurements of the Z = 2 component in the cosmic radiation provide crucial information about the propagation of charged particles through the heliosphere. The PAMELA experiment, with its long flight duration (2006 June 15-2016 January 23) and the low energy threshold (80 MeV/n) is an ideal detector for cosmic-ray solar modulation studies. In this paper, the helium nuclei spectra measured by the PAMELA instrument from 2006 July to 2009 December over a Carrington rotation time basis are presented. A state-of-the-art three-dimensional model for cosmic-ray propagation inside the heliosphere was used to interpret the time-dependent measured fluxes. Proton-to-helium flux ratio time profiles at various rigidities are also presented in order to study any features that could result from the different masses and local interstellar spectra shapes.

Keywords: Galactic cosmic rays, Cosmic ray detectors, Heliosphere
What Constraints on the Neutron Star Maximum Mass Can One Pose from GW170817 Observations?. The post-merger product of the first binary neutron star merger event detected in gravitational waves, GW170817, depends on neutron star equation of state (EoS) and is not well determined. We generally discuss the constraints one may pose on the maximum mass of a non-spinning neutron star, MTOV, based on the observations and some EoS-independent universal relations of rapidly spinning neutron stars. If the merger product is a black hole after a brief hypermassive neutron star (HMNS) phase, we derive ${M}_{\mathrm{TOV}}\lt {2.09}_{-0.09}^{+0.11}{(}_{-0.04}^{+0.06}){M}_{\odot }$ at the 2σ (1σ) level. The cases for a massive neutron star (MNS), neither a supramassive neutron star (SMNS) nor even a stable neutron star (SNS) are also allowed by the data. We derive ${2.09}_{-0.09}^{+0.11}{(}_{-0.04}^{+0.06}{M}_{\odot })\leqslant {M}_{\mathrm{TOV}}\lt {2.43}_{-0.08}^{+0.10}{(}_{-0.04}^{+0.06}){M}_{\odot }$ for the SMNS case and ${M}_{\mathrm{TOV}}\geqslant {2.43}_{-0.08}^{+0.10}{(}_{-0.04}^{+0.06}){M}_{\odot }$ for the SNS case, at the 2σ (1σ) confidence level. In the MNS cases, we also discuss the constraints on the neutron star parameters (the dipolar magnetic field strength at the surface Bp and the ellipticity ɛ) that affect the spin down history, by considering different MNS survival times, e.g., 300 s, 1 day, and 155 days after the merger, as suggested by various observational arguments. We find that once an SMNS is formed, without violating the electromagnetic observational constraints, there always exist a set of ( ${B}_{p},\epsilon $ ) parameters that allow the SMNS to survive for 300 s, 1 day, 155 days, or even longer.

Keywords: Gamma-ray bursts, Gravitational waves