Sazuna/UAT_keywords huggingface dataset:
Supernova Interaction with a Dense Detached Shell in SN 2001em. We carry out a comprehensive analysis of supernova SN 2001em covering a period of 19 yr since discovery. SN 2001em is the oldest supernova known to have undergone a metamorphosis from a stripped envelope to an interacting supernova. An early spectrum indicates it exploded as a Type Ib supernova. Later, the ejecta caught up with a dense circumstellar H-shell, ejected a few thousand years before the explosion, triggering interaction between the supernova ejecta and the dense shell, producing radio, X-ray, and Hα emission. We use archival data with the Very Large Array in radio bands and with Chandra, XMM-Newton, and Swift-XRT in X-ray bands, along with published Hα measurements. We combine these data with our low radio frequency observations with the Giant Metrewave Radio Telescope at two epochs covering three frequencies. While the observations missed the phase when the shock entered the dense shell, the X-rays indicate that the shock came out of the dense shell at around 1750 days. The data suggest a forward shock origin of the X-ray emission. Radio data show a spectral inversion at late epochs ( $\gt 5000$ days) at around 3 GHz, which mimics the properties of the central absorbed component seen in SN 1986J. A possible explanation for this component is that the progenitor of SN 2001em was a massive binary system that had undergone a period of common-envelope evolution. The hydrogen envelope from the SN 2001em progenitor may have been lost as a result of binary interaction.

Keywords: Circumstellar matter, Non-thermal radiation sources, Circumstellar shells, X-ray sources, Radio observatories, Supernovae
The Cosmic Thermal History Probed by Sunyaev-Zeldovich Effect Tomography. The cosmic thermal history, quantified by the evolution of the mean thermal energy density in the universe, is driven by the growth of structures as baryons get shock heated in collapsing dark matter halos. This process can be probed by redshift-dependent amplitudes of the thermal Sunyaev-Zeldovich (SZ) effect background. To do so, we cross-correlate eight sky intensity maps in the Planck and Infrared Astronomical Satellite missions with two million spectroscopic redshift references in the Sloan Digital Sky Surveys. This delivers snapshot spectra for the far-infrared to microwave background light as a function of redshift up to z ∼ 3. We decompose them into the SZ and thermal dust components. Our SZ measurements directly constrain $\langle {{bP}}_{{\rm{e}}}\rangle $ , the halo bias-weighted mean electron pressure, up to z ∼ 1. This is the highest redshift achieved to date, with uncorrelated redshift bins thanks to the spectroscopic references. We detect a threefold increase in the density-weighted mean electron temperature ${\overline{T}}_{{\rm{e}}}$ from 7 × 105 K at z = 1 to 2 × 106 K today. Over z = 1-0, we witness the build-up of nearly 70% of the present-day mean thermal energy density ρth, with the corresponding density parameter Ωth reaching 1.5 × 10-8. We find the mass bias parameter of Planck's universal pressure profile of B = 1.27 (or 1 - b = 1/B = 0.79), consistent with the magnitude of nonthermal pressure in gas motion and turbulence from mass assembly. We estimate the redshift-integrated mean Compton parameter y ∼ 1.2 × 10-6, which will be tested by future spectral distortion experiments. More than half originates from the large-scale structure at z &lt; 1, which we detect directly.

Keywords: Diffuse radiation, Cosmology, Large-scale structure of the universe
Absorption-line Environments of High-redshift BOSS Quasars. The early stage of massive galaxy evolution often involves outflows driven by a starburst or a central quasar plus cold mode accretion (infall), which adds to the mass build-up in the galaxies. To study the nature of these infall and outflows in the quasar environments, we have examined the correlation of narrow absorption lines (NALs) at positive and negative velocity shifts to other quasar properties, such as their broad absorption-line (BAL) outflows and radio-loudness, using spectral data from SDSS-BOSS DR12. Our results show that the incidence of associated absorption lines (AALs) and outflow AALs is strongly correlated with BALs, which indicates most AALs form in quasar-driven outflows. Multiple AALs are also strongly correlated with BALs, demonstrating quasar outflows tend to be highly structured and can create multiple gas components with different velocity shifts along our line of sight. Infall AALs appear less often in quasars with BALs than quasars without BALs. This suggests that BAL outflows act on large scale in host galaxies and inhibit the infall of gas from the IGM, supporting theoretical models in which quasar outflow plays an important role in the feedback to host galaxies. Despite having larger distances, infall AALs are more highly ionized than outflow AALs, which can be attributed to the lower densities in the infall absorbers.

Keywords: Quasar absorption line spectroscopy, Quasars
Evidence for Emergent Dark Energy. We introduce a generalized form of an emergent dark energy model with one degree of freedom for the dark energy sector that has the flexibility to include both the ΛCDM model as well as the Phenomenologically Emergent Dark Energy (PEDE) model proposed by Li &amp; Shafieloo as two of its special limits. The free parameter for the dark energy sector, namely Δ, has a value of 0 for the Λ case and a value of 1 for the PEDE case. Fitting the introduced parametric form to Planck cosmic microwave background (CMB) data and recent H0 results from local observations of cepheids and supernovae, we show that the Δ = 0 associated with the ΛCDM model would fall out of the 4&amp;sgr; confidence limits of the derived posterior of the Δ parameter. Moreover, H0 tensions with the emergent dark energy model will be alleviated and this model can satisfy the combination of Planck CMB data and local H0 observations with ΔDIC = -2.88 compared with the ΛCDM model.

Keywords: Hubble constant, Cosmological constant, Dark energy
Electron Temperature Anisotropy and Electron Beam Constraints from Electron Kinetic Instabilities in the Solar Wind. Electron temperature anisotropies and electron beams are nonthermal features of the observed nonequilibrium electron velocity distributions in the solar wind. In collision-poor plasmas these nonequilibrium distributions are expected to be regulated by kinetic instabilities through wave-particle interactions. This study considers electron instabilities driven by the interplay of core electron temperature anisotropies and the electron beam, and first gives a comprehensive analysis of instabilities in arbitrary directions to the background magnetic field. It clarifies the dominant parameter regime (e.g., parallel core electron plasma beta ${\beta }_{\mathrm{ec}\parallel }$ , core electron temperature anisotropy ${A}_{\mathrm{ec}}\equiv {T}_{\mathrm{ec}\perp }/{T}_{\mathrm{ec}\parallel }$ , and electron beam velocity Veb) for each kind of electron instability (e.g., the electron beam-driven electron acoustic/magnetoacoustic instability, the electron beam-driven whistler instability, the electromagnetic electron cyclotron instability, the electron mirror instability, the electron firehose instability, and the ordinary-mode instability). It finds that the electron beam can destabilize electron acoustic/magnetoacoustic waves in the low- ${\beta }_{\mathrm{ec}\parallel }$ regime, and whistler waves in the medium- and large- ${\beta }_{\mathrm{ec}\parallel }$ regime. It also finds that a new oblique fast-magnetosonic/whistler instability is driven by the electron beam with ${V}_{\mathrm{eb}}\gtrsim 7{V}_{A}$ in a regime where ${\beta }_{\mathrm{ec}\parallel }\sim 0.1\mbox{--}2$ and Aec &lt; 1. Moreover, this study presents electromagnetic responses of each kind of electron instability. These results provide a comprehensive overview for electron instability constraints on core electron temperature anisotropies and electron beams in the solar wind.

Keywords: Solar wind, Plasma astrophysics, Plasma physics
Star Formation and Morphological Properties of Galaxies in the Pan-STARRS 3π Survey. I. A Machine-learning Approach to Galaxy and Supernova Classification. We present a classification of galaxies in the Pan-STARRS1 (PS1) 3π survey based on their recent star formation history and morphology. Specifically, we train and test two Random Forest (RF) classifiers using photometric features (colors and moments) from the PS1 data release 2. The labels for the morphological classification are taken from Huertas-Company et al., while labels for the star formation fraction (SFF) are from the Blanton et al. catalog. We find that colors provide more predictive accuracy than photometric moments. We morphologically classify galaxies as either early- or late-type, and our RF model achieves a 78% classification accuracy. Our second model classifies galaxies as having either a low-to-moderate or high SFF. This model achieves an 89% classification accuracy. We apply both RF classifiers to the entire PS1 3π dataset, which allows us to assign two scores to each PS1 source: PHSFF, which quantifies the probability of having a high SFF; and Pspiral, which quantifies the probability of having a late-type morphology. Finally, as a proof of concept, we apply our classification framework to supernova (SN) host galaxies from the Zwicky Transient Factory and the Lick Observatory Supernova Search samples. We show that by selecting PHSFF or Pspiral, it is possible to significantly enhance or suppress the fraction of core-collapse SNe (or thermonuclear SNe) in the sample with respect to random guessing. This result demonstrates how contextual information can aid transient classifications at the time of first detection. In the current era of spectroscopically starved time-domain astronomy, prompt automated classification is paramount. Our table is available at 10.5281/zenodo.3990545.

Keywords: Core-collapse supernovae, Classification, Type Ia supernovae, Random Forests, Supernovae
Two Flares with One Shock: The Interesting Case of 3C 454.3. The quasar 3C 454.3 is a blazar known for its rapid and violent outbursts seen across the electromagnetic spectrum. Using γ-ray, X-ray, multiband optical, and very-long-baseline interferometric data we investigate the nature of two such events that occurred in 2013 and 2014 accompanied by strong variations in optical polarization, including a ∼230° electric vector position angle (EVPA) rotation. Our results suggest that a single disturbance was responsible for both flaring events. We interpret the disturbance as a shock propagating down the jet. Under this interpretation the 2013 flare originated most likely due to changes in the viewing angle caused by perhaps a bent or helical trajectory of the shock upstream of the radio core. The 2014 flare and optical polarization behavior are the result of the shock exiting the 43 GHz radio core, suggesting that shock crossings are one of the possible mechanisms for EVPA rotations.

Keywords: Radio loud quasars, Blazars, Relativistic jets, Supermassive black holes
A New Transition Wolf-Rayet WN/C Star in the Milky Way. We report the discovery of a new transition type Wolf-Rayet (W-R) WN/C star in the Galaxy. According to its coordinates (R.A., decl.)J2000 = ${18}^{{\rm{h}}}{51}^{{\rm{m}}}39\buildrel{\rm{s}}\over{.} 7$ , -05°34'51"1, and the distance (7.11 ${}_{-1.22}^{+1.56}\,$ kpc away from Earth) inferred from the second Gaia data release, it is found that W-R 121-16 is located in the Far 3 kpc Arm, and it is 3.75 kpc away from the Galactic Center. The optical spectra obtained by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope and the 2.16 m telescope, both located at the Xinglong Observatory in China, indicate that this is a W-R star of the transitional WN7o/WC subtype. A current stellar mass of about ${7.1}_{-1.1}^{+1.7}\,$ M⊙, a mass-loss rate of $\dot{M}={10}^{-{4.97}_{-0.20}^{+0.16}}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ , a bolometric luminosity of log L/L⊙ = ${4.88}_{-0.15}^{+0.17}$ , and a stellar temperature of ${T}_{* }={47}_{-5}^{+9}\,$ kK are derived by fitting the observed spectrum with a specific Potsdam W-R model. The magnitude in V-band varies between 13.95 and 14.14 mag, while no period is found. Based on the optical spectra, the time domain data, and the indices of the astrometric solution of the Gaia data, W-R 121-16 is likely a transitional WN/C single star rather than a WN+WC binary.

Keywords: Wolf-Rayet stars, Massive stars, Stellar distance, Galaxy stellar content
Standing on the Shoulders of Giants: New Mass and Distance Estimates for Betelgeuse through Combined Evolutionary, Asteroseismic, and Hydrodynamic Simulations with MESA. We conduct a rigorous examination of the nearby red supergiant Betelgeuse by drawing on the synthesis of new observational data and three different modeling techniques. Our observational results include the release of new, processed photometric measurements collected with the space-based Solar Mass Ejection Imager instrument prior to Betelgeuse's recent, unprecedented dimming event. We detect the first radial overtone in the photometric data and report a period of 185 ± 13.5 days. Our theoretical predictions include self-consistent results from multi-timescale evolutionary, oscillatory, and hydrodynamic simulations conducted with the Modules for Experiments in Stellar Astrophysics software suite. Significant outcomes of our modeling efforts include a precise prediction for the star's radius: ${764}_{-62}^{+116}\,{R}_{\odot }$ . In concert with additional constraints, this allows us to derive a new, independent distance estimate of ${168}_{-15}^{+27}$ pc and a parallax of $\pi ={5.95}_{-0.85}^{+0.58}$ mas, in good agreement with Hipparcos but less so with recent radio measurements. Seismic results from both perturbed hydrostatic and evolving hydrodynamic simulations constrain the period and driving mechanisms of Betelgeuse's dominant periodicities in new ways. Our analyses converge to the conclusion that Betelgeuse's ≈400 day period is the result of pulsation in the fundamental mode, driven by the κ-mechanism. Grid-based hydrodynamic modeling reveals that the behavior of the oscillating envelope is mass-dependent, and likewise suggests that the nonlinear pulsation excitation time could serve as a mass constraint. Our results place α Orionis definitively in the early core helium-burning phase of the red supergiant branch. We report a present-day mass of 16.5-19 M⊙—slightly lower than typical literature values.

Keywords: Stellar oscillations, Hydrodynamical simulations, Stellar evolutionary models, Red giant stars
On the Rotation of the Solar Chromosphere. Rotation is a significant characteristic of the Sun and other stars, and it plays an important role in understanding their dynamo actions and magnetic activities. In this study, the rotation of the solar chromospheric activity is investigated from a global point of view with an over 40 yr Mg II index. We determined the time-varying rotational period lengths (RPLs) with the synchrosqueezed wavelet transform, which provides high temporal and frequency resolution; furthermore, we compared the RPLs with the photospheric and coronal RPLs obtained from the sunspot numbers and the 10.7 cm radio flux data. The significance of the RPLs is taken into consideration. We found that the RPLs of the chromosphere exhibit a downward trend, as do those of the photosphere and corona; in addition, their RPLs at the recent four solar maxima also show a declining trend. This suggests that the rotation of the solar atmosphere has been accelerating during the recent four solar cycles, which is inferred to be caused by the declining strength of solar activity. The variations of the solar atmospheric RPLs show periodicities of multiple harmonics of the solar cycle period, and it is modulated by the solar activity cycle.

Keywords: Solar activity, Solar rotation, Solar chromosphere
A QPO in NGC 4945 from Archival RXTE Data. We report the discovery of an ∼6 week quasi-periodic oscillation (QPO) in archival NGC 4945 data observed by the Rossi X-ray Timing Explorer (RXTE) satellite. QPOs are important observables in accretion disks and have been studied extensively in both neutron star (NS) and black hole (BH) X-ray binaries (XRB). QPOs should be present in active galactic nuclei (AGN) if galactic BHs and supermassive black holes are governed by a common set of physical processes. The search for QPOs in AGN has proven difficult because the time scales would be much longer, due to their higher mass. RXTE AGN light curves spanning 1996 to 2011 provide an excellent and perhaps unique opportunity to search for low-frequency QPOs. We investigated the 533 RXTE observations made of the Seyfert-2 AGN, NGC 4945. During a large cluster of observations in 2006-2007 (194 observations, spanning 396 days), the Lomb-Scargle periodogram shows a candidate QPO at 0.274 μHz (period ≈42.2 days). We estimate the uncertainties using the false alarm probability. We discuss the possible identification of this feature with the Lense-Thirring precession period.

Keywords: X-ray active galactic nuclei, Active galaxies, Active galactic nuclei, High energy astrophysics
Full Transport General Relativistic Radiation Magnetohydrodynamics for Nucleosynthesis in Collapsars. We model a compact black hole-accretion disk system in the collapsar scenario with full transport, frequency dependent, general relativistic radiation magnetohydrodynamics. We examine whether or not winds from a collapsar disk can undergo rapid neutron capture (r-process) nucleosynthesis and significantly contribute to solar r-process abundances. We find the inclusion of accurate transport has significant effects on outflows, raising the electron fraction above ${Y}_{{\rm{e}}}\sim 0.3$ and preventing third-peak r-process material from being synthesized. We analyze the time evolution of neutrino processes and electron fraction in the disk and present a simple one-dimensional model for the vertical structure that emerges. We compare our simulation to semi-analytic expectations and argue that accurate neutrino transport and realistic initial and boundary conditions are required to capture the dynamics and nucleosynthetic outcome of a collapsar.

Keywords: Supernova neutrinos, Core-collapse supernovae, Gamma-ray sources, R-process, Relativistic fluid dynamics, Astrophysical black holes, Relativistic disks
Convectively Driven 3D Turbulence in Massive Star Envelopes. I. A 1D Implementation of Diffusive Radiative Transport. Massive (M &gt; 30 M⊙) stars exhibit luminosities that are near the Eddington limit for electron scattering, causing the increase in opacity associated with iron at $T\,\approx 180,000\,{\rm{K}}$ to trigger supersonic convection in their outer envelopes. Three-dimensional radiative hydrodynamics simulations by Jiang and collaborators with the Athena++ computational tool have found order-of-magnitude density and radiative flux fluctuations in these convective regions, even at optical depths $\gg 100$ . We show here that radiation can diffuse out of a parcel during the timescale of convection in these optically thick parts of the star, motivating our use of a "pseudo" Mach number to characterize both the fluctuation amplitudes and their correlations. In this first paper, we derive the impact of these fluctuations on the radiative pressure gradient needed to carry a given radiative luminosity. This implementation leads to a remarkable improvement between 1D and 3D radiative pressure gradients, and builds confidence in our path to an eventual 1D implementation of these intrinsically 3D envelopes. However, simply reducing the radiation pressure gradient is not enough to implement a new 1D model. Rather, we must also account for the impact of two other aspects of turbulent convection: the substantial pressure and the ability to transport an appreciable fraction of the luminosity, which will be addressed in upcoming works. This turbulent convection also arises in other instances where the stellar luminosity approaches the Eddington luminosity. Hence, our effort should apply to other astrophysical situations where an opacity peak arises in a near Eddington-limited, radiation pressure-dominated plasma.

Keywords: Stellar processes, Stellar structures, Stellar convection envelopes, Stellar physics, Stellar convective shells, Stellar photospheres, Stellar surfaces
Electron-impact Excitation of Fe I. The Fe I spectra emitted by astrophysical sources contain information on plasma parameters such as chemical abundances and magnetic fields. However, to determine these parameters requires detailed plasma modeling, which in turn needs accurate atomic data for processes such as radiative decay and electron-impact excitation in Fe I. A lack of fine-structure resolved collision strengths for transitions in Fe I is addressed in this paper with the presentation of data obtained from a Dirac R-matrix calculation. The suitability of our choice of target description is shown, with our energies generally within 7% of literature values. Various A-values are compared with other theoretical and experimental results, and the quality of the collision strengths produced in this work demonstrated. A comparison of 300- and 1000-level close-coupling expansions is made, the latter shown to eliminate pseudoresonances in the collision strengths at electron energies between 0.5 and 1.0 Ry. Maxwell-averaged effective collision strengths are presented, and the convergence of our data is shown in the temperature range 1000-100,000 K.

Keywords: Collision physics, De-excitation rates, Excitation rates, Atomic physics
On the Impact of Random Residual Calibration Error on the Gibbs ILC CMB Estimates over Large Angular Scales. Residual errors in calibration coefficients corresponding to observed cosmic microwave background (CMB) maps are an important issue when estimating a pure CMB signal. These errors in the input-foreground-contaminated CMB maps, if not properly taken into account in a component separation method, may lead to bias in the cleaned CMB map and estimated CMB angular power spectrum. But the inability to exactly determine the calibration coefficients corresponding to each observed CMB map from a multifrequency CMB experiment makes it very difficult to incorporate their exact and actual values during the component separation method. Hence, the effect of any random and residual calibration error in the cleaned CMB map and its angular power spectrum of a component separation problem can only be understood by performing detailed Monte Carlo simulations. In this paper, we investigate the impact of using input-observed CMB maps with random calibration errors on the posterior density of a cleaned CMB map and theoretical CMB angular power spectrum over large angular scales of the sky following the Gibbs Internal-Linear-Combination (ILC) method. By performing detailed Monte Carlo simulations of WMAP and Planck temperature anisotropy observations, including their estimate on calibration errors, we show that the best-fit map corresponding to the posterior maximum is minimally biased in the Gibbs ILC method by a CMB normalization bias and residual foreground bias. The residual calibration-induced error in the best-fit power spectrum causes an overall 6% increase of the net error when added in quadrature with the cosmic-variance-induced error.

Keywords: Posterior distribution, Gibbs Sampler, Cosmic microwave background radiation