Sazuna/UAT_keywords huggingface dataset:
Search for Eccentric Binary Neutron Star Mergers in the First and Second Observing Runs of Advanced LIGO. We present a search for gravitational waves from merging binary neutron stars (BNSs) which have non-negligible eccentricity as they enter the Laser Interferometer Gravitational Wave Observatory (LIGO) observing band. We use the public Advanced LIGO data which covers the period from 2015 through 2017 and contains ∼164 days of LIGO-Hanford and LIGO-Livingston coincident observing time. The search was conducted using matched-filtering using the PyCBC toolkit. We find no significant BNS candidates beyond GW170817, which has previously been reported by searches for binaries in circular orbits. We place a 90% upper limit of ∼1700 mergers Gpc-3 yr-1 for eccentricities ≲0.43 at a dominant-mode gravitational-wave frequency of 10 Hz. The absence of a detection with these data is consistent with theoretical predictions of eccentric BNS merger rates. Using our measured rate we estimate the sensitive volume of future gravitational-wave detectors and compare this to theoretical rate predictions. We find that, in the absence of a prior detection, the rate limits set by six months of Cosmic Explorer observations would constrain all current plausible models of eccentric BNS formation.

Keywords: Neutron stars, Elliptical orbits, Gravitational waves, Compact objects
Final Spitzer IRAC Observations of the Rise and Fall of SN 1987A. Spitzer's final Infrared Array Camera observations of SN 1987A show the 3.6 and 4.5 μm emission from the equatorial ring (ER) continues a period of steady decline. Deconvolution of the images reveals that the emission is dominated by the ring, not the ejecta, and is brightest on the west side. Decomposition of the marginally resolved emission also confirms this, and shows that the west side of the ER has been brightening relative to the other portions of the ER. The infrared morphological changes resemble those seen in both the soft X-ray emission and the optical emission. The integrated ER light curves at 3.6 and 4.5 μm are more similar to the optical light curves than the soft X-ray light curve, though differences would be expected if dust is responsible for this emission and its destruction is rapid. Future observations with the James Webb Space Telescope will continue to monitor the ER evolution, and will reveal the true spectrum and nature of the material responsible for the broadband emission at 3.6 and 4.5 μm. The present observations also serendipitously reveal a nearby variable source, subsequently identified as a Be star, that has gone through a multiyear outburst during the course of these observations.

Keywords: Core-collapse supernovae, Light curves, Deconvolution, Large Magellanic Cloud, Supernova remnants, Infrared astronomy, Be stars, Circumstellar dust
Microlensing Analysis for the Gravitational Lens Systems SDSS0924+0219, Q1355-2257, and SDSS1029+2623. We use spectroscopic observations of the gravitationally lensed systems SDSS0924+0219(BC), Q1355-2257(AB), and SDSS1029+2623(BC) to analyze microlensing and dust extinction in the observed components. We detect chromatic microlensing effects in the continuum and microlensing in the broad emission line profiles of the systems SDSS0924+0219(BC) and Q1355-2257(AB). Using magnification maps to simulate microlensing and modeling the emitting region as a Gaussian intensity profile with size rs ∝ λp, we obtain the probability density functions for a logarithmic size prior to ${\lambda }_{\mathrm{rest} \mbox{-} \mathrm{frame}}=3533\,\mathring{\rm A} $ . In the case of SDSS0924+0219, we obtain ${r}_{s}={4}_{-2}^{+3}\,\sqrt{M/{M}_{\odot }}$ lt-d (at 1σ), which is larger than the range of other estimates, and p = 0.8 ± 0.2 (at 1σ), which is smaller than predicted by the thin disk theory, but still in agreement with previous results. In the case of Q1355-2257 we obtain (at 1σ) ${r}_{s}={3.6}_{-1.6}^{+3.0}\,\sqrt{M/{M}_{\odot }}$ lt-d, which is also larger than the theoretical prediction, and p = 2.0 ± 0.7, which is in agreement with the theory within errors. SDSS1029+2326 spectra show evidence of extinction, probably produced by a galaxy in the vicinity of image C. Fitting an extinction curve to the data we estimate ∆E ∼ 0.2 in agreement with previous results. We found no evidence of microlensing for this system.

Keywords: Quasar microlensing, Strong gravitational lensing, Quasars
Solitons and Turbulence in Solar Wind at 1 au: Multi-satellite Data and FDTD Simulations. During 2015 January 1-31 multi-satellite data at 1 au showed the propagation of single soliton pulses, the formation of soliton trains, and their ultimate development into the turbulence in solar wind magnetic field, density, speed, temperature, and dynamic pressure. This work is motivated by a basic research question: what are the differences in the conditions for excitation of soliton pulse, soliton train, and turbulence in the solar wind? To answer this question, a convective and dispersive system is considered and simulated via the finite difference time domain (FDTD) method. It is found that when a system is initially driven by a weak shock wave only a single soliton pulse will propagate. When the convection coefficient is smaller than or equal to the dispersion coefficient and system is driven by a strong shock then soliton trains are formed. The development of turbulence occurs when the convective coefficient dominates the dispersion coefficient and the system is driven by a stronger shock. Combining the findings of FDTD simulations with the Hall magnetohydrodynamic model, it is concluded that an enhanced interplanetary magnetic field in the magnetic sheath and the declining ion density after corotation interaction region interface provide favorable conditions for the solitons formation. Contrarily, the declining magnetic field in ejecta provides pertinent conditions for the evolution of Alfvénic turbulence. Our findings are critical for understanding the wave development into turbulence in solar wind.

Keywords: Slow solar wind, Ejecta, Fast Fourier transform, Fast solar wind, Interplanetary turbulence, Solar storm, Solar wind, Alfven waves, Solar coronal mass ejections, Shocks, Corotating streams, Interplanetary physics
Spatially Resolved Analysis of Neutral Winds, Stars, and Ionized Gas Kinematics with MEGARA/GTC: New Insights on the Nearby Galaxy UGC 10205. We present a comprehensive analysis of the multiphase structure of the interstellar medium (ISM) and the stellar kinematics in the edge-on nearby galaxy UGC 10205 using integral field spectroscopy (IFS) data taken with Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía (MEGARA) at the GTC. We explore both the neutral and the ionized gas phases using the interstellar Na I D doublet absorption (LR-V setup, R ∼ 6000) and the Hα emission line (HR-R setup, R ∼ 18000), respectively. The high-resolution data show the complexity of the Hα emission-line profile revealing the detection of up to three kinematically distinct gaseous components. Despite of this fact, a thin-disk model is able to reproduce the bulk of the ionized gas motions in the central regions of UGC 10205. The use of asymmetric drift corrections is needed to reconciliate the ionized and the stellar velocity rotation curves. We also report the detection of outflowing neutral gas material blueshifted by ∼ 87 km s-1. The main physical properties that describe the observed outflow are a total mass Mout = (4.55 ± 0.06) × 107 M⊙ and a cold-gas mass outflow rate ${\dot{M}}_{\mathrm{out}}=0.78\pm 0.03$ M ˙ out = 0.78 ± 0.03 M⊙ yr-1. This work points out the necessity of exploiting high-resolution IFS data to understand the multiphase components of the ISM and the multiple kinematical components in the central regions of nearby galaxies.

Keywords: Stellar kinematics, Galaxy winds, Spectroscopy, Extragalactic astronomy, Galaxies
A Curious Case of Circular Polarization in the 25 GHz Methanol Maser Line toward OMC-1. We report the detection of a circular polarization signature in the Stokes V profile of a 25 GHz Class I CH3OH maser toward the high-mass star-forming region OMC-1. Such a feature usually constitutes a detection of the Zeeman effect. If due to a magnetic field in OMC-1, this would represent the first detection and discovery of the Zeeman effect in the 25 GHz Class I CH3OH maser. The feature in Stokes V is detected in two observations with different angular resolutions taken eight years apart with the Very Large Array; for our 2009 D-configuration observations, the fitted value for z ${B}_{\mathrm{los}}$ is 152 ± 12 Hz, where z is the Zeeman splitting factor and ${B}_{\mathrm{los}}$ is the line-of-sight magnetic field. For our 2017 C-configuration observations, the fitted value for z ${B}_{\mathrm{los}}$ = 149 ± 19 Hz, likely for the same maser spot. These correspond to ${B}_{\mathrm{los}}$ in the range 171-214 mG, depending on which hyperfine transition is responsible for the maser line. While these ${B}_{\mathrm{los}}$ values are high, they are not implausible. If the magnetic field increases in proportion to the molecular hydrogen density in shocked regions, then our detected fields predict values for the pre-shock magnetic field that are in agreement with observations. With ${B}_{\mathrm{los}}$ = 171-214 mG, the magnetic energy in the post-shocked regions where these 25 GHz Class I CH3OH masers occur would dominate over the kinetic energy density and be at least of the order of the pressure in the shock, implying that the magnetic field would exert significant influence over the dynamics of these regions.

Keywords: Interstellar molecules, High resolution spectroscopy, Star forming regions, Interstellar magnetic fields, Star formation, Astrophysical masers, Interstellar medium, Polarimetry
Large-scale Structures in the CANDELS Fields: The Role of the Environment in Star Formation Activity. We present a robust method, weighted von Mises kernel density estimation, along with boundary correction to reconstruct the underlying number density field of galaxies. We apply this method to galaxies brighter than Hubble Space Telescope $/{\rm{F}}160{\rm{w}}\leqslant 26$ AB mag in the redshift range 0.4 ≤ z ≤ 5 in the five CANDELS fields (GOODS-N, GOODS-S, EGS, UDS, and COSMOS). We then use these measurements to explore the environmental dependence of the star formation activity of galaxies. We find strong evidence of environmental quenching for massive galaxies (M ≳ 1011 M⊙) out to z ∼ 3.5 such that an overdense environment hosts ≳20% more massive quiescent galaxies than an underdense region. We also find that environmental quenching efficiency grows with stellar mass and reaches ∼60% for massive galaxies at z ∼ 0.5. The environmental quenching is also more efficient than stellar mass quenching for low-mass galaxies (M ≲ 1010 M⊙) at low and intermediate redshifts (z ≲ 1.2). Our findings concur thoroughly with the "overconsumption" quenching model where the termination of cool gas accretion (cosmological starvation) happens in an overdense environment and the galaxy starts to consume its remaining gas reservoir in depletion time. The depletion time depends on the stellar mass and could explain the evolution of environmental quenching efficiency with stellar mass.

Keywords: Large-scale structure of the universe, Galaxy quenching, Galaxy evolution, Galaxy environments
LIGO/Virgo Sources from Merging Black Holes in Ultradwarf Galaxies. The origins of the black hole-black hole mergers discovered through gravitational waves with the LIGO/Virgo Collaboration are a mystery. We investigate the idea that some of these black holes originate from the centers of extremely low mass ultradwarf galaxies that have merged together in the distant past at z &gt; 1. Extrapolating the central black hole/stellar mass ratio suggests that the black holes in these mergers could arise from galaxies of masses ∼105-106 M⊙. We investigate whether these galaxies merge at a rate consistent with the observed black hole rate of ∼9.7-101 Gpc-3 yr-1 using the latest LIGO/Virgo results. We show that in the nearby universe the merger rate and number densities of ultradwarf galaxies are too low, by an order or magnitude, to produce these black hole mergers. However, by considering that the merger fraction, merger timescales, and the number densities of low-mass galaxies all conspire at z &gt; 1-1.5 to increase the merger rate for these galaxies at higher redshifts, we argue that it is possible that these observed gravitational wave events could arise from black holes in the centers of low-mass galaxies. The major uncertainty in this calculation is the merger dynamical timescales for black holes in low-mass galaxies. Our results suggest that a very long black hole merger timescale of 4-7 Gyr is needed, consistent with an extended merger history. Further simulations of black hole merger timescales are needed to test this possibility; however, our theory can be tested by searching for host galaxies of gravitational wave events. Results from these searches will put limits on dwarf galaxy mergers and/or the presence and formation mechanisms of black holes through Population III stars in the lowest-mass galaxies.

Keywords: Intermediate-mass black holes, Supermassive black holes, Dwarf galaxies, Galaxy mergers, Gravitational waves, Galaxy evolution, LIGO
Fermi and Swift Observations of GRB 190114C: Tracing the Evolution of High-energy Emission from Prompt to Afterglow. We report on the observations of gamma-ray burst (GRB) 190114C by the Fermi Gamma-ray Space Telescope and the Neil Gehrels Swift Observatory. The prompt gamma-ray emission was detected by the Fermi GRB Monitor (GBM), the Fermi Large Area Telescope (LAT), and the Swift Burst Alert Telescope (BAT) and the long-lived afterglow emission was subsequently observed by the GBM, LAT, Swift X-ray Telescope (XRT), and Swift UV Optical Telescope. The early-time observations reveal multiple emission components that evolve independently, with a delayed power-law component that exhibits significant spectral attenuation above 40 MeV in the first few seconds of the burst. This power-law component transitions to a harder spectrum that is consistent with the afterglow emission observed by the XRT at later times. This afterglow component is clearly identifiable in the GBM and BAT light curves as a slowly fading emission component on which the rest of the prompt emission is superimposed. As a result, we are able to observe the transition from internal-shock- to external-shock-dominated emission. We find that the temporal and spectral evolution of the broadband afterglow emission can be well modeled as synchrotron emission from a forward shock propagating into a wind-like circumstellar environment. We estimate the initial bulk Lorentz factor using the observed high-energy spectral cutoff. Considering the onset of the afterglow component, we constrain the deceleration radius at which this forward shock begins to radiate in order to estimate the maximum synchrotron energy as a function of time. We find that even in the LAT energy range, there exist high-energy photons that are in tension with the theoretical maximum energy that can be achieved through synchrotron emission from a shock. These violations of the maximum synchrotron energy are further compounded by the detection of very high-energy (VHE) emission above 300 GeV by MAGIC concurrent with our observations. We conclude that the observations of VHE photons from GRB 190114C necessitates either an additional emission mechanism at very high energies that is hidden in the synchrotron component in the LAT energy range, an acceleration mechanism that imparts energy to the particles at a rate that is faster than the electron synchrotron energy-loss rate, or revisions of the fundamental assumptions used in estimating the maximum photon energy attainable through the synchrotron process.

Keywords: Gamma-ray bursts
Continuous Null-point Magnetic Reconnection Builds Up a Torus Unstable Magnetic Flux Rope Triggering the X9.3 Flare in Solar AR 12673. Two X-class solar flares occurred on 2017 September 6 from active region NOAA 12673: the first one is a confined X2.2 flare, and it is followed only ∼3 hr later by the second one, which is the strongest flare in solar cycle 24, reaching X9.3 class and accompanied by a coronal mass ejection. Why did these two X-class flares occur in the same position with similar magnetic configurations, but one is eruptive while the other is not? Here we track the coronal magnetic field evolution via nonlinear force-free field extrapolations from a time sequence of vector magnetograms with high cadence. A detailed analysis of the magnetic field shows that a magnetic flux rope (MFR) forms and grows gradually before the first flare, and shortly afterward, the MFR's growth is significantly enhanced with a much faster rise in height, from far below the threshold of torus instability to above it, while the magnetic twist only increases mildly. Combining EUV observations and the magnetic field extrapolation, we found that overlying the MFR is a null-point magnetic topology, where recurrent brightening is seen after the first flare. We thus suggest a scenario to interpret the occurrence of the two flares. The first flare occurred since the MFR reached a high enough height to activate the null point, and its continuous expansion forces the null-point reconnection recurrently. Such reconnection weakens the overlying field, allowing the MFR to rise faster, which eventually crosses the threshold of torus instability and triggers the second, eruptive flare.

Keywords: Solar flares, Solar magnetic reconnection, Solar active regions, Solar coronal mass ejections, Solar filament eruptions, Magnetic fields
Limits on Mode Coherence in Pulsating DA White Dwarfs Due to a Nonstatic Convection Zone. The standard theory of pulsations deals with the frequencies and growth rates of infinitesimal perturbations in a stellar model. Modes that are calculated to be linearly driven should increase their amplitudes exponentially with time; the fact that nearly constant amplitudes are usually observed is evidence that nonlinear mechanisms inhibit the growth of finite-amplitude pulsations. Models predict that the mass of convection zones in pulsating hydrogen-atmosphere (DAV) white dwarfs is very sensitive to temperature (I.e., ${M}_{\mathrm{CZ}}\propto {T}_{\mathrm{eff}}^{-90}$ ), leading to the possibility that even low-amplitude pulsators may experience significant nonlinear effects. In particular, the outer turning point of finite-amplitude g-mode pulsations can vary with the local surface temperature, producing a reflected wave that is out of phase with what is required for a standing wave. This can lead to a lack of coherence of the mode and a reduction in its global amplitude. In this paper we show that (1) whether a mode is calculated to propagate to the base of the convection zone is an accurate predictor of its width in the Fourier spectrum, (2) the phase shifts produced by reflection from the outer turning point are large enough to produce significant damping, and (3) amplitudes and periods are predicted to increase from the blue edge to the middle of the instability strip, and subsequently decrease as the red edge is approached. This amplitude decrease is in agreement with the observational data while the period decrease has not yet been systematically studied.

Keywords: Stellar interiors, White dwarf stars, Analytical mathematics, Computational methods, DA stars, Stellar oscillations
Predicting Coronal Mass Ejections Using SDO/HMI Vector Magnetic Data Products and Recurrent Neural Networks. We present two recurrent neural networks (RNNs), one based on gated recurrent units and the other based on long short-term memory, for predicting whether an active region (AR) that produces an M- or X-class flare will also produce a coronal mass ejection (CME). We model data samples in an AR as time series and use the RNNs to capture temporal information on the data samples. Each data sample has 18 physical parameters, or features, derived from photospheric vector magnetic field data taken by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory. We survey M- and X-class flares that occurred from 2010 to 2019 May using the Geostationary Operational Environmental Satellite's X-ray flare catalogs provided by the National Centers for Environmental Information (NCEI), and select those flares with identified ARs in the NCEI catalogs. In addition, we extract the associations of flares and CMEs from the Space Weather Database of Notifications, Knowledge, Information. We use the information gathered above to build the labels (positive versus negative) of the data samples at hand. Experimental results demonstrate the superiority of our RNNs over closely related machine learning methods in predicting the labels of the data samples. We also discuss an extension of our approach to predict a probabilistic estimate of how likely an M- or X-class flare is to initiate a CME, with good performance results. To our knowledge this is the first time that RNNs have been used for CME prediction.

Keywords: Solar activity, Solar active regions, Solar flares, Solar coronal mass ejections
Interplanetary Protons versus Interacting Protons in the 2017 September 10 Solar Eruptive Event. We analyze the relativistic proton emission from the Sun during the eruptive event on 2017 September 10, which caused a ground-level enhancement (GLE 72) registered by the worldwide network of neutron monitors. Using the neutron monitor data and interplanetary transport modeling both along and across interplanetary magnetic field (IMF) lines, we deduce parameters of the proton injection into the interplanetary medium. The inferred injection profile of the interplanetary protons is compared with the profile of the &gt;100 MeV γ-ray emission observed by the Fermi Large Area Telescope, attributed to pion production from the interaction of &gt;300 MeV protons at the Sun. GLE 72 started with a prompt component that arrived along the IMF lines. This was followed by a more prolonged enhancement caused by protons arriving at the Earth across the IMF lines from the southwest. The interplanetary proton event is modeled using two sources—one source at the root of the Earth-connected IMF line and another source situated near the solar western limb. The maximum phase of the second injection of interplanetary protons coincides with the maximum phase of the prolonged &gt;100 MeV γ-ray emission that originated from a small area at the solar western limb, below the current sheet trailing the associated coronal mass ejection (CME). A possible common source of interacting protons and interplanetary protons is discussed in terms of proton acceleration at the CME bow shock versus coronal (re-)acceleration in the wake of the CME.

Keywords: Solar flares, Solar energetic particles, Solar gamma-ray emission, Solar coronal mass ejection shocks, Solar coronal mass ejections, Solar particle emission