Sazuna/UAT_keywords huggingface dataset:
Fe VII Emission Lines in the Wavelength Range 193-197 Å. The identifications of Fe VII emission lines in the wavelength range 193-197 Å are discussed in the light of new measurements of laboratory spectra and atomic data calculations. This region is of importance to studies of solar spectra from the EUV Imaging Spectrometer (EIS) on board the Hinode spacecraft, which has its peak sensitivity at these wavelengths. Ten lines are measured, arising from seven fine structure levels in the 3p53d3 configuration. Two lines have not previously been reported and lead to new experimental energies for the ${({a}^{2}D)}^{3}{F}_{\mathrm{2,3}}$ levels. Updated experimental energies are obtained for the remaining levels. The new atomic model is used to compute theoretical values for the two density diagnostic ratios λ196.21/λ195.39 and λ196.21/λ196.06, and densities are derived from EIS spectra of coronal loop footpoints.

Keywords: Solar extreme ultraviolet emission, Atomic spectroscopy, Spectroscopy, Solar transition region, Line intensities
A Single-pulse Study of PSR J1022+1001 Using the FAST Radio Telescope. Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we have recorded ∼105 single pulses from PSR J1022+1001. We studied the polarization properties, their energy distribution, and their times of arrival. This is only possible with the high sensitivity available using FAST. There is no indication that PSR J1022+1001 exhibits giant pulse, nulling, or traditional mode changing phenomena. The energy in the leading and trailing components of the integrated profile is shown to be correlated. The degree of both linear and circular polarization increases with the pulse flux density for individual pulses. Our data indicates that pulse jitter leads to an excess noise in the timing residuals of 67 ns when scaled to one hour, which is consistent with Liu et al. We have unsuccessfully trialed various methods to improve timing precision through the selection of specific single pulses. Our work demonstrates that FAST can detect individual pulses from pulsars that are observed in order to detect and study gravitational waves. This capability enables detailed studies, and parameterization, of the noise processes that affect the sensitivity of a pulsar timing array.

Keywords: Astronomy data analysis, Pulsars
Final Compact Remnants in Core-collapse Supernovae from 20 to 40 M<SUB>⊙</SUB>: The Lower Mass Gap. A mass paucity of compact objects in the range of ∼2-5 M⊙ has been suggested by X-ray binary observations, namely, the "lower mass gap." Gravitational wave detections have unlocked another mass measurement method, and aLIGO/Virgo has observed some candidates in the gap. We revisit the numerical simulations on the core-collapse supernovae (CCSNe) for ∼20-40 M⊙ progenitor stars with different initial explosion energies. As a result, the lower explosion energy naturally causes more efficient fallback accretion for low-metallicity progenitors, and then the newborn black holes (BHs) in the center of the CCSNe can escape from the gap, but neutron stars cannot easily collapse into BHs in the gap; nevertheless, the final remnants of the solar-metallicity progenitors stick to the gap. If we consider that only drastic CCSNe can be observed and that those with lower explosion energies are universal, the lower mass gap can be reasonably built. The width and depth of the gap are mainly determined by the typical CCSN initial explosion energy and metallicity. One can expect that the future multimessenger observations of compact objects delineate the shape of the gap, which might constrain the properties of the CCSNe and their progenitors.

Keywords: Accretion, Neutron stars, Stellar mass black holes, Core-collapse supernovae
Detecting Reconnection Events in Kinetic Vlasov Hybrid Simulations Using Clustering Techniques. Kinetic turbulence in magnetized space plasmas has been extensively studied via in situ observations, numerical simulations, and theoretical models. In this context, a key point concerns the formation of coherent current structures and their disruption through magnetic reconnection. We present automatic techniques aimed at detecting reconnection events in a large data set of numerical simulations. We make use of clustering techniques known as K-means and DBscan (usually referred to in literature as unsupervised machine-learning approaches), and other methods based on thresholds of standard reconnection proxies. All our techniques also use a threshold on the aspect ratio of the regions selected. We test the performance of our algorithms. We propose an optimal aspect ratio to be used in the automated machine-learning algorithm: AR = 18. The performance of the unsupervised approach results in it being strongly competitive with respect to those of other methods based on thresholds of standard reconnection proxies.

Keywords: Astronomy data modeling, Solar magnetic reconnection, Astronomy data analysis, Computational methods, Clustering
Physical and Chemical Structure of the Disk and Envelope of the Class 0/I Protostar L1527. Submillimeter spectral line and continuum emission from the protoplanetary disks and envelopes of protostars is a powerful probe of their structure, chemistry, and dynamics. Here we present a benchmark study of our modeling code, RadChemT, that for the first time uses a chemical model to reproduce ALMA C18O (2-1), and CARMA 12CO (1-0) and N2H+ (1-0) observations of L1527; this allows us to distinguish the disk, the infalling envelope, and outflow of this Class 0/I protostar. RadChemT combines dynamics, radiative transfer, gas chemistry, and gas-grain reactions to generate models that can be directly compared with observations for individual protostars. Rather than individually fit abundances to a large number of free parameters, we aim to best match the spectral line maps by (i) adopting a physical model based on density structure and luminosity derived primarily from previous work that fit spectral energy distribution and 2D imaging data, updating it to include a narrow jet detected in CARMA and ALMA data near (≤75 au) the protostar, and then (ii) computing the resulting astrochemical abundances for 292 chemical species. Our model reproduces the C18O and N2H+ line strengths within a factor of 3.0; this is encouraging considering the pronounced abundance variation (factor &gt;103) between the outflow shell and CO snowline region near the midplane. Further, our modeling confirms suggestions regarding the anticorrelation between N2H+ and the CO snowline between 400 au and 2000 au from the central star. Our modeling tools represent a new and powerful capability with which to exploit the richness of spectral line imaging provided by modern submillimeter interferometers.

Keywords: Spectral line identification, Astrochemistry, Molecular physics, Star formation, Radiative transfer, Protostars
Luminosity Functions and Host-to-host Scatter of Dwarf Satellite Systems in the Local Volume. Low-mass satellites around Milky Way (MW)-like galaxies are important probes of small-scale structure and galaxy formation. However, confirmation of satellite candidates with distance measurements remains a key barrier to fast progress in the Local Volume (LV). We measure the surface brightness fluctuation distances to recently cataloged candidate dwarf satellites around 10 massive hosts within D &lt; 12 Mpc to confirm association. The satellite systems of these hosts are complete and mostly cleaned of contaminants down to Mg ∼ -9 to -10, within the area of the search footprints. Joining this sample with hosts surveyed to comparable or better completeness in the literature, we explore how well cosmological simulations combined with common stellar to halo mass relations (SHMR) match observed satellite luminosity functions in the classical satellite luminosity regime. Adopting an SHMR that matches hydrodynamic simulations, we find that the predicted overall satellite abundance agrees well with the observations. The MW is remarkably typical in its luminosity function among LV hosts. We find that the host-to-host scatter predicted by the model is in close agreement with the scatter between the observed systems, once the different masses of the observed systems are taken into account. However, we find significant evidence that the observed systems have more bright and fewer faint satellites than the SHMR model predicts, possibly necessitating a higher normalization of the SHMR around halo masses of 1011 M⊙ or significantly greater scatter than present in common SHMRs. These results demonstrate the utility of nearby satellite systems in inferring the galaxy-subhalo connection in the low-mass regime.

Keywords: Luminosity function, Galaxy dark matter halos, Galaxy distances, Dwarf galaxies
On the Thermally Pulsing Asymptotic Giant Branch Contribution to the Light of Nearby Disk Galaxies. The study of the luminosity contribution from thermally pulsing asymptotic giant branch (TP-AGB) stars to the stellar populations of galaxies is crucial to determine their physical parameters (e.g., stellar mass and age). We use a sample of 84 nearby disk galaxies to explore diverse stellar population synthesis models with different luminosity contributions from TP-AGB stars. We fit the models to optical and near-infrared (NIR) photometry, on a pixel-by-pixel basis. The statistics of the fits show a preference for a low-luminosity contribution (i.e., high mass-to-light ratio in the NIR) from TP-AGB stars. Nevertheless, for 30%-40% of the pixels in our sample a high-luminosity contribution (hence low mass-to-light ratio in the NIR) from TP-AGB stars is favored. According to our findings, the mean TP-AGB star luminosity contribution in nearby disk galaxies may vary with Hubble type. This may be a consequence of the variation of the TP-AGB mass-loss rate with metallicity, if metal-poor stars begin losing mass earlier than metal-rich stars, because of a pre-dust wind that precedes the dust-driven wind.

Keywords: Spiral galaxies, Galaxy stellar content, Asymptotic giant branch stars, Galaxy photometry, Galaxy evolution
Detection of Energy Cutoffs in Flare-accelerated Electrons. Energy cutoffs in electron distribution define the lower and upper limits on the energy range of energetic electrons accelerated in solar flares. They are crucial parameters for understanding particle acceleration processes and energy budgets. Their signatures have been reported in studies of flattened flare X-ray spectra, i.e., the impulsive emission of nonthermal bremsstrahlung from energetic electrons impacting ambient, thermal plasma. However, these observations have not provided unambiguous constraints on the cutoffs. Moreover, other processes may result in similar spectral features. Even the existence and necessity of cutoffs as physical parameters of energetic electrons have been under debate. Here we report a search for their signatures in flare-accelerated electrons with two approaches, i.e., in both X-ray spectra and solar energetic particle (SEP) events. These represent two different electron populations, but may contain information of the same acceleration process. By studying a special group of late impulsive flares, and a group of selected SEP events, we found evidence of cutoffs revealed in both X-ray spectra and SEP electron distributions. In particular, we found for the first time consistent low- and high-energy cutoffs in both hard X-ray-producing and escaping electrons in two events. We also showed the importance of high-energy cutoff in studies of spectral shapes. These results provide evidence of cutoffs in flare-accelerated energetic electrons and new clues for constraining electron distribution parameters and particle acceleration models.

Keywords: Solar flares, Solar flare spectra, Solar x-ray emission, X-ray telescopes, Solar x-ray flares
Formation of Dust Filaments in the Diffuse Envelopes of Molecular Clouds. The path to understanding star formation processes begins with the study of the formation of molecular clouds. The outskirts of these clouds are characterized by low column densities that allow the penetration of ultraviolet radiation, resulting in a nonnegligible ionization fraction and the charging of the small dust grains that are mixed with the gas; this diffuse phase is then coupled to the ambient magnetic field. Despite the general assumption that dust and gas are tightly correlated, several observational and theoretical studies have reported variations in the dust-to-gas ratio toward diffuse and cold clouds. In this work, we present the implementation of a new charged particles module for analyzing the dust dynamics in molecular cloud envelopes. We study the evolution of a single population of small charged grains (0.05 μm) in the turbulent, magnetized molecular cloud envelope using this module. We show that variations in the dust-to-gas ratio arise due to the coupling of the grains with the magnetic field, forming elongated dust structures decoupled from the gas. This emphasizes the importance of considering the dynamics of charged dust when simulating the different phases of the interstellar medium, especially for star formation studies.

Keywords: Interstellar dust, Warm neutral medium, Interstellar clouds, Star formation
Medium-band Observation of the Neutrino Emitting Blazar, TXS 0506+056. TXS 0506+056 is a blazar that has been recently identified as the counterpart of the neutrino event IceCube-170922A. Understanding the blazar type of TXS 0506+056 is important to constrain the neutrino emission mechanism, but the blazar nature of TXS 0506+056 is still uncertain. As an attempt to understand the nature of TXS 0506+056, we report the medium-band observation results of TXS 0506+056, covering the wavelength range of 0.575-1.025 μm. The use of the medium-band filters allows us to examine if there were any significant changes in its spectral shapes over the course of one month and give a better constraint on the peak frequency of synchrotron radiation with quasi-simultaneous data sets. The peak frequency is found to be 1014.28 Hz, and our analysis shows that TXS 0506+056 is not an outlier from the blazar sequence. As a way to determine the blazar type, we also analyzed if TXS 0506+056 is bluer-when-brighter (BL Lac type and some flat spectrum radio quasars, FSRQs) or redder-when-brighter (found only in some FSRQs). Even though we detect no significant variability in the spectral shape larger than observational error during our medium-band observation period, the comparison with a data set taken in 2012 shows a possible redder-when-brighter behavior of FSRQs. Our results demonstrate that medium-band observations with small to moderate-sized telescopes can be an effective way to trace the spectral evolution of transients such as TXS 0506+056.

Keywords: BL Lacertae objects, Blazars, Neutrino astronomy, Active galaxies, Medium band photometry, Active galactic nuclei, Astronomical instrumentation, Time domain astronomy
A Simplified Photodynamical Model for Planetary Mass Determination in Low-eccentricity Multitransiting Systems. Inferring planetary parameters from transit timing variations (TTVs) is challenging for small exoplanets because their transits may be so weak that determination of individual transit timing is difficult or impossible. We implement a useful combination of tools that together provide a numerically fast global photodynamical model. This is used to fit the TTV-bearing light curve, in order to constrain the masses of transiting exoplanets in low-eccentricity, multiplanet systems—and small planets in particular. We present inferred dynamical masses and orbital eccentricities in four multi-planet systems from Kepler's complete long-cadence data set. We test our model against Kepler-36/KOI-277, a system with some of the most precisely determined planetary masses through TTV inversion methods, and find masses of 5.56+0.41-0.45 and 9.76+0.79-0.89 ${m}_{\oplus }$ for Kepler-36 b and c, respectively—consistent with literature in both value and error. We then improve the mass determination of the four planets in Kepler-79/KOI-152, where literature values were physically problematic to 12.5+4.5-3.6, 9.5+2.3-2.1, 11.3+2.2-2.2 and 6.3+1.0-1.0 ${m}_{\oplus }$ for Kepler-79 b, c, d, and e, respectively. We provide new mass constraints where none existed before for two systems. These are 12.5+3.2-2.6 ${m}_{\oplus }$ for Kepler-450 c, and 3.3+1.7-1.0 and 17.4+7.1-3.8 ${m}_{\oplus }$ for Kepler-595 c (previously KOI-547.03) and b, respectively. The photodynamical code used here, called PyDynamicaLC, is made publicly available.

Keywords: Exoplanet astronomy, Mini Neptunes, Super Earths, Exoplanets
Re-estimating the Spin Parameter of the Black Hole in Cygnus X-1. Cygnus X-1 is a well-studied persistent black hole X-ray binary. Recently, the three parameters needed to estimate the black hole spin of this system, namely the black hole mass M, the orbital inclination i, and the source distance D, have been updated. In this work we redetermine the spin parameter using the continuum-fitting technique for those updated parameter values. Based on the assumption that the spin axis of the black hole is aligned with the orbital plane, we fit the thermal disk component to a fully relativistic thin accretion disk model. The error in the spin estimate arising from the combined observational uncertainties is obtained via Monte Carlo simulations. We demonstrate that, without considering the counteracting torque effect, the new spin parameter is constrained to be a* &gt; 0.9985 (3σ), which confirms that the spin of the black hole in Cygnus X-1 is extreme.

Keywords: Black hole physics, X-ray binary stars, High energy astrophysics
Wind Mass-loss Rates of Stripped Stars Inferred from Cygnus X-1. Recent observations of the high-mass X-ray binary Cygnus X-1 have shown that both the companion star (41 solar masses) and the black hole (21 solar masses) are more massive than previously estimated. Furthermore, the black hole appears to be nearly maximally spinning. Here, we present a possible formation channel for the Cygnus X-1 system that matches the observed system properties. In this formation channel, we find that the orbital parameters of Cygnus X-1, combined with the observed metallicity of the companion, imply a significant reduction in mass loss through winds relative to commonly used prescriptions for stripped stars.

Keywords: Stellar winds, High mass x-ray binary stars, Stellar mass black holes
WIYN Open Cluster Study. LXXXIV. The Effect of Chromospheric Activity on Oxygen Abundances from the 7774 Å Triplet in Pleiades Dwarfs. We present a spectroscopic analysis of 7774 Å O I triplet abundances, 8498-8662 Å Ca II triplet chromospheric activity, and rotation in the Pleiades open cluster, with the objective of thoroughly examining the O triplet overabundance trends observed in cool open cluster dwarfs, and to thereby make clear the cause of that trend. High-dispersion, contemporaneous spectra of the O I triplet, Ca II triplet, and Hα spectral regions in 41 Pleiades dwarfs were acquired using Hydra on the WIYN 3.5 m telescope. Our Ca II emission equivalent-width data exhibit a strong positive correlation with decreasing Teff, with the rapidly rotating stars enhanced by up to 50% above the slowly rotating stars. Our triplet [O/H] values exhibit a statistically significant positive correlation with total Ca II triplet emission, and similarly, significant correlations have been found by every study to date that used contemporaneous O triplet abundance and chromospheric activity data, which is strong evidence that chromospheric activity is the cause of the observed overabundance trends. Based on the slowly rotating, low Ca II emission stars in the near-solar range 5450 K &lt; Teff &lt; 6100 K, we find a cluster mean [O/H] = + 0.143 ± 0.061, consistent with the substantial super-solar [O/H] values exhibited by most young ( &lt; 1 Gyr) open clusters. We also find a cluster mean [Fe/H] = + 0.029 ± 0.034, in excellent agreement with previous studies.

Keywords: Open star clusters, Stellar abundances, Stellar activity
The MOSDEF Survey: Environmental Dependence of the Gas-phase Metallicity of Galaxies at 1.4 ≤ z ≤ 2.6. Using the near-IR spectroscopy of the MOSFIRE Deep Evolution Field survey, we investigate the role of the local environment in the gas-phase metallicity of galaxies. The local environment measurements are derived from accurate and uniformly calculated photometric redshifts with well-calibrated probability distributions. Based on rest-frame optical emission lines, [N II]λ6584 and Hα, we measure gas-phase oxygen abundances of 167 galaxies at 1.37 ≤ z ≤ 1.7 and 303 galaxies at 2.09 ≤ z ≤ 2.61, located in diverse environments. We find that at z ∼ 1.5, the average metallicity of galaxies in overdensities with M* ∼ 109.8 M⊙, 1010.2 M⊙, and 1010.8 M⊙ is higher relative to their field counterparts by 0.094 ± 0.051, 0.068 ± 0.028, and 0.052 ± 0.043 dex, respectively. However, this metallicity enhancement does not exist at higher redshift, z ∼ 2.3, where, compared to the field galaxies, we find 0.056 ± 0.043, 0.056 ± 0.028, and 0.096 ± 0.034 dex lower metallicity for galaxies in overdense environments with M* ∼ 109.8 M⊙, 1010.2 M⊙ and 1010.7 M⊙, respectively. Our results suggest that, at 1.37 ≤ z ≤ 2.61, the variation of mass-metallicity relation with local environment is small (&lt;0.1 dex), and reverses at z ∼ 2. Our results support the hypothesis that, at the early stages of cluster formation, owing to efficient gas cooling, galaxies residing in overdensities host a higher fraction of pristine gas with prominent primordial gas accretion, which lowers their gas-phase metallicity compared to their coeval field galaxies. However, as the universe evolves to lower redshifts (z ≲ 2), the shock-heated gas in overdensities cannot cool down efficiently, and galaxies become metal-rich rapidly due to the suppression of pristine gas inflow and re-accretion of metal-enriched outflows in overdensities. * Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation.

Keywords: Metallicity, Large-scale structure of the universe, Galaxy environments, Galaxy evolution, High-redshift galaxies
A Comparison of Star-forming Clumps and Tidal Tails in Local Mergers and High-redshift Galaxies. The Clusters, Clumps, Dust, and Gas in Extreme Star-forming Galaxies (CCDG) survey with the Hubble Space Telescope includes multiwavelength imaging of 13 galaxies less than 100 Mpc away, spanning a range of morphologies and sizes, from blue compact dwarfs to luminous infrared galaxies, all with star formation rates in excess of hundreds of solar masses per year. Images of seven merging galaxies in the CCDG survey were artificially redshifted to compare with galaxies at z = 0.5, 1, and 2. Most redshifted tails have surface brightnesses that would be visible at z = 0.5 or 1 but not at z = 2 due to cosmological dimming. Giant star clumps are apparent in these galaxies; the 51 measured have similar sizes, masses, and colors to clumps in observed high-z systems in the UDF, GEMS, GOODS, and CANDELS surveys. These results suggest that some clumpy high-z galaxies without observable tidal features could be the result of mergers. The local clumps also have the same star formation rate per unit area and stellar surface density as clumps observed at intermediate and high redshift, so they provide insight into the substructure of distant clumps. A total of 1596 star clusters brighter than MV = -9 were identified within the boundaries of the local clumps. The cluster magnitude distribution function is a power law with approximately the same slope (∼-1 for a plot of number versus log luminosity) for all the galaxies both inside and outside the clumps and independently of clump surface brightness.

Keywords: Interacting galaxies, Starburst galaxies, High-redshift galaxies, Galaxy evolution