Sazuna/UAT_keywords huggingface dataset:
Sunspot Characteristics at the Onset of the Maunder Minimum Based on the Observations of Hevelius. An analysis of the sunspot observations made by Hevelius during 1642-1645 is presented. These records are the only systematic sunspot observations just before the Maunder Minimum (MM). We have studied different phenomena meticulously recorded by Hevelius after translating the original Latin texts. We reevaluate the observations of sunspot groups by Hevelius during this period and obtain an average value 7% greater than that calculated from his observations given in the current group database. Furthermore, the average of the active day fraction obtained in this work from Hevelius’s records previous to the MM is significantly greater than the solar activity level obtained from Hevelius’s sunspot observations made during the MM (70% versus 30%). We also present the butterfly diagram obtained from the sunspot positions recorded by Hevelius for the period 1642-1645. It can be seen that no hemispheric asymmetry exists during this interval, in contrast with the MM. Hevelius noted a ∼3-month period that appeared to lack sunspots in early 1645 that gave the first hint of the impending MM. Recent studies claim that the MM was not a grand minimum period, speculating that astronomers of that time, due to the Aristotelian ideas, did not record all sunspots that they observed, producing thus an underestimation of the solar activity level. However, we show that the good quality of the sunspot records made by Hevelius indicates that his reports of sunspots were true to the observations.

Keywords: Solar activity, The Sun, Sunspots, Maunder minimum
Lyα Observations of High Radial Velocity Low-mass Stars Ross 1044 and Ross 825. The discovery of habitable zone (HZ) planets around low-mass stars has highlighted the need for a comprehensive understanding of the radiation environments in which such planets reside. Of particular importance is knowledge of the far-ultraviolet (FUV) radiation, as low-mass stars are typically much more active than solar-type stars and the proximity of their HZs can be one-tenth the distance. The vast majority of the flux emitted by low-mass stars at FUV wavelengths occurs in the Lyα line at 1216 Å. However, measuring a low-mass star’s Lyα emission directly is almost always impossible because of the contaminating effects of interstellar hydrogen and geocoronal airglow. We observed Ross 825 (K3) and Ross 1044 (M0), two stars with exceptional radial velocities, with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. Their radial velocities resulted in significant line shifts, allowing for a more complete view of their Lyα line profiles. We provide an updated relation between effective temperature and Lyα flux using Gaia DR2 astrometry as well as updated, model-independent relationships between Lyα flux and UV flux measurements from the Galaxy Evolution Explorer (GALEX) for low-mass stars. These new relations, in combination with GALEX's considerable spatial coverage, provide substantial predictive power for the Lyα environments for thousands of nearby, low-mass stars.

Keywords: Low mass stars
Evolution of ONeMg Core in Super-AGB Stars toward Electron-capture Supernovae: Effects of Updated Electron-capture Rate. Stars with ∼8-10 M ⊙ evolve to form a strongly degenerate ONeMg core. When the core mass becomes close to the Chandrasekhar mass, the core undergoes electron captures on 24Mg and 20Ne that induce an electron-capture supernova (ECSN). In order to clarify whether the ECSN leads to a collapse or thermonuclear explosion, we calculate the evolution of an 8.4 M ⊙ star from the main sequence until the oxygen ignition in the ONeMg core. We apply the latest electron-capture rate on 20Ne, including the second forbidden transition, and investigate how the location of the oxygen ignition (center or off-center) and the Y  e  distribution depend on the input physics and the treatment of the semiconvection and convection. The central density when the oxygen deflagration is initiated, ρ c,def, can be significantly higher than that of the oxygen ignition thanks to the convection, and we estimate {log}}10({ρ }{{c},{def}}/{{g}} {cm}}-3)&gt; 10.10. We perform two-dimensional simulations of the flame propagation to examine how the final fate of the ONeMg core depends on the Y  e  distribution and ρ c,def. We find that the deflagration starting from {log}}10({ρ }{{c},{def}}/{{g}} {cm}}-3)&gt; 10.01(&lt; 10.01) leads to a collapse (thermonuclear explosion). Since our estimate of ρ c,def exceeds this critical value, the ONeMg core is likely to collapse, although further studies of the convection and semiconvection before the deflagration are important.

Keywords: Supernovae, Late stellar evolution, Nuclear reaction cross sections
A Two-zone Model for Blazar Emission: Implications for TXS 0506+056 and the Neutrino Event IceCube-170922A. A high-energy muon neutrino event, IceCube-170922A, was recently discovered in both spatial and temporal coincidence with a gamma-ray flare of the blazar TXS 0506+056. It has been shown with standard one-zone models that neutrinos can be produced in the blazar jet via hadronic interactions, but with a flux that is mostly limited by the X-ray data. In this work, we explore the neutrino production from TXS 0506+056 by invoking two physically distinct emission zones in the jet, with an inner blob inside of or close to the broad-line region (BLR) and an outer one well beyond the BLR. Using the Doppler-boosted radiation of the BLR as the target photon field, the inner zone accounts for the neutrino and gamma-ray emission via pγ interactions and inverse Compton scattering, respectively, while the outer zone produces the optical and X-ray emission via synchrotron and synchrotron self-Compton processes. The different conditions of the two zones allow us to suppress the X-ray emission from the electromagnetic cascade, and set a much higher upper limit on the muon neutrino flux (i.e., ∼10-11 erg cm-2 s-1) than in one-zone models. We compare our scenario in detail with one-zone models discussed in the literature, and argue that differentiating between such scenarios will become possible with next-generation neutrino telescopes, such as IceCube-Gen2.

Keywords: High energy astrophysics, High-energy cosmic radiation, Gamma-ray sources, Blazars, Neutrino astronomy
A Search for Late-time Radio Emission and Fast Radio Bursts from Superluminous Supernovae. We present results of a search for late-time radio emission and fast radio bursts (FRBs) from a sample of type-I superluminous supernovae (SLSNe-I). We used the Karl G. Jansky Very Large Array to observe 10 SLSN-I more than 5 yr old at a frequency of 3 GHz. We searched fast-sampled visibilities for FRBs and used the same data to perform a deep imaging search for late-time radio emission expected in models of magnetar-powered supernovae. No FRBs were found. One SLSN-I, PTF10hgi, is detected in deep imaging, corresponding to a luminosity of 1.2 × 1028 erg s-1. This luminosity, considered with the recent 6 GHz detection of PTF10hgi in Eftekhari et al., supports the interpretation that it is powered by a young, fast-spinning (∼ms spin period) magnetar with ∼15 M ⊙ of partially ionized ejecta. Broadly, our observations are most consistent with SLSNe-I being powered by neutron stars with fast spin periods, although most require more free-free absorption than is inferred for PTF10hgi. We predict that radio observations at higher frequencies or in the near future will detect these systems and begin constraining properties of the young pulsars and their birth environments.

Keywords: Extragalactic radio sources, Radio bursts, Radio interferometry, Supernovae
The Atmospheric Circulation of Ultra-hot Jupiters. Recent observations of ultra-hot Jupiters with dayside temperatures in excess of 2500 K have found evidence for new physical processes at play in their atmospheres. In this work, we investigate the effects of the dissociation of molecular hydrogen and recombination of atomic hydrogen on the atmospheric circulation of ultra-hot Jupiters. To do so, we incorporate these effects into a general circulation model (GCM) for hot Jupiter atmospheres and run a large suite of models varying the incident stellar flux, rotation period, and strength of frictional drag. We find that including hydrogen dissociation and recombination reduces the fractional day-to-night temperature contrast of ultra-hot Jupiter atmospheres and causes the speed of the equatorial jet to decrease in simulations with fixed rotation. This is because the large energy input required for hydrogen dissociation cools the dayside of the planet, and the energy released due to hydrogen recombination warms the nightside. The resulting decrease in the day-to-night temperature contrast reduces the day-to-night pressure gradient that drives the circulation, resulting in weaker wind speeds. The results from our GCM experiments qualitatively agree with previous theory that found that the fractional day-night temperature contrast of ultra-hot Jupiters should decrease with increasing equilibrium temperature owing to hydrogen dissociation and recombination. Lastly, we compute full-phase light curves from our suite of GCM experiments, finding that the reduced day-to-night temperature contrast in ultra-hot Jupiter atmospheres causes a smaller phase curve amplitude. The reduction in phase curve amplitude due to hydrogen dissociation and recombination could explain the relatively small phase curve amplitudes of observed ultra-hot Jupiters.

Keywords: Hydrodynamics, Exoplanet atmospheres, Hot Jupiters
Type IIP Supernova Progenitors and Their Explodability. I. Convective Overshoot, Blue Loops, and Surface Composition. We present the evolution of massive star progenitors of supernovae of type IIP. We take the example of the nearby and well-studied SN 2013ej. We explore how convective overshoot affects the stellar structure, surface abundances, and effective temperature of massive stars, using the Modules for Experiments in Stellar Astrophysics. In particular, models with moderate overshoot (f = 0.02-0.031) show the presence of blue loops in the Hertzsprung-Russell diagram with a red to blue excursion (log10[T eff/K] from &lt;3.6 to &gt;4.0) and transition back to red, during the core helium-burning phase. Models with overshoot outside this range of f values kept the star in the red supergiant state throughout the post-helium-ignition phases. The surface CNO abundance shows enrichment post-main-sequence and again around the time when helium is exhausted in the core. These evolutionary changes in surface CNO abundance are indistinguishable in the currently available observations due to large observational uncertainties. However, these observations may distinguish between the ratio of surface nitrogen to oxygen at different evolutionary stages of the star. We also compare the effects of convective overshoot on various parameters related to likelihood of explosion of a star as opposed to collapse to a black hole. These parameters are the compactness parameter, M 4, and μ 4. The combination μ 4 × M 4, and μ 4 have similar variations with f and both peak at f = 0.032. We find that all of our 13 {M}⊙  models are likely to explode.

Keywords: Stellar convective zones, Core-collapse supernovae, Blue loop, Type II supernovae, Massive stars, Stellar evolutionary models, Computational methods, Supergiant stars
Understanding the Discrepancy between IRX and Balmer Decrement in Tracing Galaxy Dust Attenuation. We compare the infrared excess (IRX) and Balmer decrement ({{H}}α /{{H}}β ) as dust attenuation indicators in relation to other galaxy parameters using a sample of ∼32,000 local star-forming galaxies (SFGs) carefully selected from the Sloan Digital Sky Survey, the Galaxy Evolution Explorer, and the Wide-field Infrared Survey Explore. While at fixed {{H}}α /{{H}}β , IRX turns out to be independent on galaxy stellar mass, the Balmer decrement does show a strong mass dependence at fixed IRX. We find the discrepancy, parameterized by the color excess ratio {R}EBV}\equiv E{(B-V)}IRX}/E{(B-V)}{{H}α /{{H}}β }, is not dependent on the gas-phase metallicity and axial ratio, but on the specific star formation rate (SSFR) and galaxy size (R e) following {R}EBV}=0.79+0.15{log}({SSFR}/{R}{{e}}2). This finding reveals that the nebular attenuation as probed by the Balmer decrement becomes increasingly larger than the global (stellar) attenuation of SFGs with decreasing SSFR surface density. This can be understood in the context of an enhanced fraction of intermediate-age stellar populations that are less attenuated by dust than the H II region-traced young population, in conjunction with a decreasing dust opacity of the diffuse interstellar matter when spreading over a larger spatial extent. Once the SSFR surface density of an SFG is known, the conversion between attenuation of nebular and stellar emission can be well estimated using our scaling relation.

Keywords: Extinction, Star formation, Galaxy evolution, Interstellar medium
Fast Outflows Identified in Early Star-forming Galaxies at z = 5-6. We present velocities of galactic outflows in seven star-forming galaxies at z = 5-6 with stellar masses of M * ∼ 1010.1 {M}⊙ . Although it is challenging to observationally determine the outflow velocities, we overcome this by using ALMA [C II] 158 μm emission lines for systemic velocities and deep Keck spectra with metal absorption lines for velocity profiles available to date. We construct a composite Keck spectrum of the galaxies at z = 5-6 with the [C II]-systemic velocities, and fit outflow-line profiles to the Si II λ1260, C II λ1335, and Si IV λλ1394,1403 absorption lines in the composite spectrum. We measure the maximum (90%) and central outflow velocities to be {v}\max ={700}-110+180 {km} {{{s}}}-1 and {v}out}={400}-150+100 {km} {{{s}}}-1 on average, respectively, showing no significant differences between the outflow velocities derived with the low- to high-ionization absorption lines. For M * ∼ 1010.1 {M}⊙ , we find that the {v}\max  value of our z = 5-6 galaxies is 3 times higher than those of z ∼ 0 galaxies and comparable to z ∼ 2 galaxies. Estimating the halo circular velocity {v}cir} from the stellar masses and the abundance matching results, we investigate a {v}\max -{v}cir} relation. Interestingly, {v}\max  for galaxies with M * = 1010.0-10.8 {M}⊙  shows a clear positive correlation with {v}cir} and/or the galaxy star formation rate over z = 0-6 with a small scatter of ≃ +/- 0.1 dex, which is in good agreement with theoretical predictions. This positive correlation suggests that the outflow velocity is physically related to the halo circular velocity, and that the redshift evolution of {v}\max  at fixed M * is explained by the increase in {v}cir} toward high redshift.

Keywords: High-redshift galaxies, Galaxy formation, Galaxy winds, Galaxy evolution
A Carbon-rich Hot Bubble in the Planetary Nebula NGC 5189. We present the discovery of extended X-ray emission from the planetary nebula (PN) NGC 5189 around the [WO1]-type WD 1330-657 with XMM-Newton. The X-ray-emitting gas fills the cavities detected in the Hubble Space Telescope [O III] narrowband image and presents a limb-brightened morphology toward the outer edges of the east and west lobes. The bulk of the X-ray emission is detected in the soft (0.3-0.7 keV) band with the XMM-Newton EPIC spectra dominated by the C VI Lyα line at 0.37 keV (=33.7 Å). Spectral analysis resulted in carbon and neon abundances 38 and 6 times their solar values, with a plasma temperature of kT = 0.14 ± 0.01 keV (T = 1.6 × 106 K) and X-ray luminosity of L X = (2.8 ± 0.8) × 1032 erg s-1. NGC 5189 is an evolved and extended PN (≲0.70 pc in radius), thus, we suggest that the origin of its X-ray emission is consistent with the born-again scenario in which the central star becomes carbon-rich through an eruptive very late thermal pulse, subsequently developing a fast, carbon-rich wind powering the X-ray emission as suggested for A 30 and A 78.

Keywords: Stellar wind bubbles, Stellar winds, Planetary nebulae, X-ray sources, Wolf-Rayet stars
The Mass-Metallicity Relation at z ∼ 0.8: Redshift Evolution and Parameter Dependency. The spectra of emission-line galaxies from the extended Baryon Oscillation Spectroscopic Survey of the Sloan Digit Sky Survey (SDSS) are used to study the mass-metallicity relation (MZR) at z ∼ 0.8. The selected sample contains about 180,000 massive star-forming galaxies with 0.6 &lt; z &lt; 1.05 and 9&lt; {log}({M}\star /{M}⊙ )&lt; 12. The spectra are stacked in bins of different parameters including redshift, stellar mass, star formation rate (SFR), specific star formation rate (sSFR), half-light radius, mass density, and optical color. The average MZR at z ∼ 0.83 has a downward evolution in the MZR from the local to high-redshift universe, which is consistent with previous works. At a specified stellar mass, galaxies with higher SFR/sSFR and larger half-light radius have systematically lower metallicity. This behavior is reversed for galaxies with larger mass density and optical color. Among the above physical parameters, the MZR has the most significant dependency on SFR. Our galaxy sample at 0.6 &lt; z &lt; 1.05 approximately follows the fundamental metallicity relation (FMR) in the local universe, although the sample inhomogeneity and incompleteness might have an effect on our MZR and FMR.

Keywords: Galaxy abundances, Emission line galaxies, Scaling relations
Frequency Distribution of Acoustic Oscillation in the Solar Atmosphere During Flare Event. We present a study of multi-wavelength observations, of a C 2.3 solar flare in Active Region NOAA 12353, observed on 2015 May 23, which reveal new properties of acoustic waves in the flaring region. The space-, and ground-based data measured by the HELioseismological Large Regions Interferometric Device, operating at the Vacuum Tower Telescope, the Atmospheric Imaging Assembly (AIA), and Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory, were used in this paper. First, using power spectra of solar oscillations, we identified the dominant frequencies and their location at seven different atmospheric levels before and after the flare event. Second, based on AIA observations taken in six Extreme Ultraviolet filters, we derived Differential Emission Measure (DEM) profiles and DEM maps of the flare. Finally, we confirm the sigma shape of the magnetic field in the active area, directly related to the flare. Our results are as follows: the high-frequency waves (ν &gt; 5 mHz) in the photosphere, in both cases, before and after the flare, are generated at the footpoints of the chromospheric loop, while in the chromosphere (Hα line), before the event the power enhancement exhibits the maximum of flare emission, and after the eruption the enhancement by all frequencies is observed only in the post-flare loop area. Moreover, the power of oscillation in the pores surrounding the area before the flare has a random character, while after the flare oscillation power is concentrated in the pore, and weakened outside of. We conclude that accurate detection of high-frequency acoustic waves in active regions can lead to faster and easier prediction of high-energy events.

Keywords: Solar atmosphere, Solar flares, Helioseismology, Solar physics, Solar magnetic fields
Mid-IR Variability and Dust Reverberation Mapping of Low-z Quasars. I. Data, Methods, and Basic Results. The continued operation of the Wide-field Infrared Survey Explorer (WISE), combined with several ground-based optical transient surveys (e.g., CRTS, ASAS-SN, and PTF), offers an unprecedented opportunity to explore the dust structures in luminous active galactic nuclei (AGNs). We use these data for a mid-IR dust reverberation mapping (RM) study of 87 archetypal Palomar-Green quasars at z ≲ 0.5. To cope with various contaminations of the photometry data and the sparse time sampling of the light curves, procedures to combine these data sets and retrieve the dust RM signals have been developed. We find that ∼70% of the sample (with a completeness correction up to 95%) has convincing mid-IR time lags in the WISE W1 (∼3.4 μm) and W2 (∼4.5 μm) bands, and they are proportional to the square root of the AGN luminosity. Combined with previous K-band (∼2.2 μm) RM results in the literature, the inferred dust emission size ratios are {R}K:{R}W1:{R}W2=0.6:1:1.2. Under simple assumptions, we put preliminary constraints on the projected dust surface density at these bands and reveal the possibly different torus structures among hot-dust-deficient, warm-dust-deficient, and normal quasars from the reverberation signals. With multi-epoch Spitzer data and later WISE photometry, we also explore AGN IR variability at 10-24 μm over a 5 yr timescale. Except for blazars and flat-spectrum radio sources, the majority of AGNs have typical variation amplitudes at 24 μm of no more than 10% of that in the W1 band, indicating that the dust reverberation signals damp out quickly at longer wavelengths. In particular, steep-spectrum radio quasars also lack strong 24 μm variability, consistent with the unification picture of radio-loud AGNs.

Keywords: Supermassive black holes, Quasars, Reverberation mapping, Radio quiet quasars, Radio loud quasars, Infrared astronomy, Active galactic nuclei, Dust continuum emission, Infrared galaxies, Extragalactic astronomy, Time series analysis
Age Determination of Galactic B-type Stars in Double-lined Eclipsing Binaries. We present the results of age determination for galactic B-type main-sequence stars that are components of double-lined eclipsing binaries. Only detached systems are considered. We analyze 38 binary systems that meet such criteria. The analysis is based on evolutionary computations, and we consider that the age is determined if there is a common value from the radius-age diagrams and the agreement in the position of both components in the Hertzsprung-Russell diagram. In some cases, to meet these two conditions, it was necessary to adjust the value of the metallicity, Z, or/and the parameter of overshooting from the convective core, α ov. We determine a consistent age for 33 of the 38 binaries. Additionally, we completed extensive computations, and for each system, we give the range of α ov and Z for which a consistent solution exists. The age of the studied B-type main-sequence stars ranges, as counted from the Zero Age Main Sequence, from about 2.5 Myr to about 200 Myr.

Keywords: Spectroscopic binary stars, Early-type stars, Eclipsing binary stars, Stellar evolutionary models