Sazuna/UAT_keywords huggingface dataset:
Spitzer Microlensing Parallax Reveals Two Isolated Stars in the Galactic Bulge. We report the mass and distance measurements of two single-lens events from the 2017 Spitzer microlensing campaign. The ground-based observations yield the detection of finite-source effects, and the microlens parallaxes are derived from the joint analysis of ground-based observations and Spitzer observations. We find that the lens of OGLE-2017-BLG-1254 is a 0.60 ± 0.03 M⊙ star with DLS = 0.53 ± 0.11 kpc, where DLS is the distance between the lens and the source. The second event, OGLE-2017-BLG-1161, is subject to the known satellite parallax degeneracy, and thus is either a 0.51-0.10+0.12 M_{⊙} star with DLS = 0.40 ± 0.12 kpc or a 0.38-0.12+0.13 M_{⊙} star with DLS = 0.53 ± 0.19 kpc. Both of the lenses are therefore isolated stars in the Galactic bulge. By comparing the mass and distance distributions of the eight published Spitzer finite-source events with the expectations from a Galactic model, we find that the Spitzer sample is in agreement with the probability of finite-source effects occurring in single-lens events.

Keywords: Gravitational microlensing, Stellar distance, Satellite microlensing parallax, Stellar masses
The MASSIVE Survey. XV. A Stellar Dynamical Mass Measurement of the Supermassive Black Hole in Massive Elliptical Galaxy NGC 1453. We present a new stellar dynamical mass measurement (M_{BH}) of the supermassive black hole (SMBH) in NGC 1453, a fast-rotating massive elliptical galaxy in the MASSIVE survey. We measure stellar kinematics in 135 spatial bins in the central 1.5 kpc × 2 kpc region of the galaxy using high signal-to-noise ratio (S/N ∼ 130) spectra from the Gemini-North GMOS integral field spectrograph (IFS). Combining with wide-field IFS kinematics out to ∼3 effective radii and stellar light distributions from Hubble Space Telescope Wide Field Camera 3 images, we perform Schwarzschild orbit-based mass modeling in the axisymmetric limit to constrain the mass components in NGC 1453. The best-fit black hole mass is M_{BH}=(2.9± 0.4)× 10^{9} M_{☉}; the mass models without a central black hole are excluded at the 8.7σ level. The NGC 1453 black hole lies within the intrinsic scatter of the SMBH and galaxy scaling relations, unlike three other galaxies hosting ≳ 10^{10} M_{☉} SMBHs in the MASSIVE sample. The high-S/N GMOS spectra enable us to determine eight moments of the Gauss-Hermite expansion of the line-of-sight velocity distributions (LOSVDs), which are used as constraints in the orbit modeling. The stellar orbits in the mass models are further constrained to produce negligible h9 through h12 to minimize spurious behavior in the LOSVDs. We show that truncating the series at h4, as was often done in prior work, leads to a much weaker constraint on the inferred M_{BH} for NGC 1453. Furthermore, we discuss precautions and modifications that are needed to achieve axisymmetry in triaxial orbit codes that use the Schwarzschild method to sample the start space of stellar orbits in triaxial gravitational potentials.

Keywords: Galaxy dynamics, Galaxy structure, Galaxy kinematics, Galaxy evolution, Elliptical galaxies, Dark matter, Galaxies
Laminar Flame Speeds in Degenerate Oxygen-Neon Mixtures. The collapse of degenerate oxygen-neon cores (I.e., electron-capture supernovae or accretion-induced collapse) proceeds through a phase in which a deflagration wave ("flame") forms at or near the center and propagates through the star. In models, the assumed speed of this flame influences whether this process leads to an explosion or to the formation of a neutron star. We calculate the laminar flame speeds in degenerate oxygen-neon mixtures with compositions motivated by detailed stellar evolution models. These mixtures include trace amounts of carbon and have a lower electron fraction than those considered in previous work. We find that trace carbon has little effect on the flame speeds, but that material with electron fraction Y_{e} ≈ 0.48-0.49 has laminar flame speeds that are ≈ 2 times faster than those at Y_{e}=0.5. We provide tabulated flame speeds and a corresponding fitting function so that the impact of this difference can be assessed via full star hydrodynamical simulations of the collapse process.

Keywords: White dwarf stars, Oxygen burning, Degenerate matter
Realistic On-the-fly Outcomes of Planetary Collisions. II. Bringing Machine Learning to N-body Simulations. Terrestrial planet formation theory is at a bottleneck, with the growing realization that pairwise collisions are treated far too simply. Here, and in our companion paper that introduces the training methodology, we demonstrate the first application of machine learning to more realistically model the late stage of planet formation by giant impacts. We present surrogate models that give fast, reliable answers for the masses and velocities of the two largest remnants of a giant impact, as a function of the colliding masses and their impact velocity and angle, with the caveat that our training data do not yet include pre-impact rotation or variable thermal conditions. We compare canonical N-body scenarios of terrestrial planet formation assuming perfect merger with our more realistic treatment that includes inefficient accretions and hit-and-run collisions. The result is a protracted tail of final events lasting ∼200 Myr, and the conversion of about half the mass of the initial population to debris. We obtain profoundly different solar system architectures, featuring a much wider range of terrestrial planet masses and enhanced compositional diversity.

Keywords: Planetary system formation, Open source software, Solar system terrestrial planets, Planet formation
Extremely Long Convergence Times in a 3D GCM Simulation of the Sub-Neptune Gliese 1214b. We present gray gas general circulation model (GCM) simulations of the tidally locked mini-Neptune GJ 1214b. On timescales of 1000-10,000 Earth days, our results are comparable to previous studies of the same planet, in the sense that they all exhibit two off-equatorial eastward jets. Over much longer integration times (50,000-250,000 Earth days) we find a significantly different circulation and observational features. The zonal-mean flow transitions from two off-equatorial jets to a single wide equatorial jet that has higher velocity and extends deeper. The hot spot location also shifts eastward over the integration time. Our results imply a convergence time far longer than the typical integration time used in previous studies. We demonstrate that this long convergence time is related to the long radiative timescale of the deep atmosphere and can be understood through a series of simple arguments. Our results indicate that particular attention must be paid to model convergence time in exoplanet GCM simulations, and that other results on the circulation of tidally locked exoplanets with thick atmospheres may need to be revisited.

Keywords: Hot Jupiters, Exoplanets, Atmospheric circulation, Hot Neptunes, Planetary atmospheres, Mini Neptunes, Extrasolar gaseous giant planets, Exoplanet atmospheres
Stellar Metallicities from SkyMapper Photometry I: A Study of the Tucana II Ultra-faint Dwarf Galaxy. We present a study of the ultra-faint Milky Way dwarf satellite galaxy Tucana II using deep photometry from the 1.3 m SkyMapper telescope at Siding Spring Observatory, Australia. The SkyMapper filter set contains a metallicity-sensitive intermediate-band V filter covering the prominent Ca II K feature at 3933.7 Å. When combined with photometry from the SkyMapper u, g, and I filters, we demonstrate that V-band photometry can be used to obtain stellar metallicities with a precision of ∼0.20 dex when [Fe/H] &gt; -2.5, and ∼0.34 dex when [Fe/H] &lt; -2.5. Since the u and V filters bracket the Balmer Jump at 3646 Å, we also find that the filter set can be used to derive surface gravities. We thus derive photometric metallicities and surface gravities for all stars down to a magnitude of g ∼ 20 within ∼75' of Tucana II. Photometric metallicity and surface gravity cuts remove nearly all foreground contamination. By incorporating Gaia proper motions, we derive quantitative membership probabilities that recover all known members of the red giant branch of Tucana II. Additionally, we identify multiple likely new members in the center of the system, as well as candidate members several half-light radii from the center of the system. Finally, we present a metallicity distribution function derived from the photometric metallicities of likely Tucana II members. This result demonstrates the utility of wide-field imaging with the SkyMapper filter set in studying ultra-faint dwarf galaxies, and in general, low surface brightness populations of metal-poor stars. Upcoming work will clarify the membership status of several distant stars identified as candidate members of Tucana II.

Keywords: Local Group, Stellar abundances, Dwarf galaxies
Search for PeV Gamma-Ray Emission from the Southern Hemisphere with 5 Yr of Data from the IceCube Observatory. The measurement of diffuse PeV gamma-ray emission from the Galactic plane would provide information about the energy spectrum and propagation of Galactic cosmic rays, and the detection of a pointlike source of PeV gamma-rays would be strong evidence for a Galactic source capable of accelerating cosmic rays up to at least a few PeV. This paper presents several unbinned maximum-likelihood searches for PeV gamma-rays in the Southern Hemisphere using 5 yr of data from the IceTop air shower surface detector and the in-ice array of the IceCube Observatory. The combination of both detectors takes advantage of the low muon content and deep shower maximum of gamma-ray air showers and provides excellent sensitivity to gamma-rays between ∼0.6 and 100 PeV. Our measurements of pointlike and diffuse Galactic emission of PeV gamma-rays are consistent with the background, so we constrain the angle-integrated diffuse gamma-ray flux from the Galactic plane at 2 PeV to 2.61 × 10-19 cm-2 s-1 TeV-1 at 90% confidence, assuming an E-3 spectrum, and we estimate 90% upper limits on pointlike emission at 2 PeV between 10-21 and 10-20 cm-2 s-1 TeV-1 for an E-2 spectrum, depending on decl. Furthermore, we exclude unbroken power-law emission up to 2 PeV for several TeV gamma-ray sources observed by the High Energy Spectroscopic System and calculate upper limits on the energy cutoffs of these sources at 90% confidence. We also find no PeV gamma-rays correlated with neutrinos from IceCube's high-energy starting event sample. These are currently the strongest constraints on PeV gamma-ray emission.

Keywords: Galactic cosmic rays, Gamma-rays, Particle astrophysics, Cosmic rays
Predicting Solar Flares Using a Novel Deep Convolutional Neural Network. Space weather forecasting is very important, and the prediction of space weather, especially for solar flares, has increasingly attracted research interests with the numerous recent breakthroughs in machine learning. In this study, we propose a novel convolutional neural network (CNN) model to make binary class prediction for both ≥C-class and ≥M-class flares within 24 hr. We collect magnetogram samples of solar active regions (ARs) provided by the Space-weather Helioseismic and Magnetic Imager Active Region Patches (SHARP) data from 2010 May to 2018 September. These samples are used to construct 10 separate data sets. Then, after training, validating, and testing our model, we compare the results of our model with previous studies in several metrics, with a focus on the true skill statistic (TSS). The major results are summarized as follows. (1) We propose a method of shuffle and split cross-validation (CV) based on AR segregation, which is the first attempt to verify the validity and stability of the model in flare prediction. (2) The proposed CNN model achieves a relatively high score of TSS = 0.749 ± 0.079 for ≥M-class prediction, and TSS = 0.679 ± 0.045 for ≥C-class prediction, which is greatly improved compared with previous studies. (3) The model trained on 10 CV data sets is considerably robust and stable in making flare prediction for both ≥C class and ≥M class. Our experimental results indicate that our proposed CNN model is a highly effective method for flare forecasting, with quite excellent prediction performance.

Keywords: Solar flares, Convolutional neural networks, Astronomical techniques, Solar activity, Magnetic fields
Revealing the Double Nucleus of NGC 4490. NGC 4490/85 (UGC 7651/48) or Arp 269 is well known for being one of the closest interacting/merging galactic systems. NGC 4490 has a high star formation rate (SFR) and is surrounded by an enormous H I feature stretching about 60 kpc north and south of the optically visible galaxies. Both the driver for the high SFR in NGC 4490 and the formation mechanism of the H I structure are puzzling aspects of this system. We have used mid-infrared Spitzer data to show that NGC 4490 has a double nucleus morphology. One nucleus is visible in the optical, while the other is only visible at infrared and radio wavelengths. We find the optical nucleus and the potential infrared visible nucleus have similar sizes, masses, and luminosities. Both are comparable in mass and luminosity to other nuclei found in interacting galaxy pairs and much more massive and luminous compared with typical nonnuclear star-forming complexes. We examine possible origin scenarios for the infrared feature, and conclude that it is likely that NGC 4490 is itself a merger remnant, which is now interacting with NGC 4485. This earlier encounter provides both a possible driver for extended star formation in NGC 4490, and multiple pathways for the formation of the extended H I plume.

Keywords: Galaxy formation, Galaxy mergers, Galaxy structure, Galaxy evolution
A Joint Mass-Radius-Period Distribution of Exoplanets. The radius-period distribution of exoplanets has been characterized by the Kepler survey, and the empirical mass-radius relation by the subset of Kepler planets with mass measurements. We combine the two in order to constrain the joint mass-radius-period distribution of Kepler transiting planets. We employ hierarchical Bayesian modeling and mixture models to formulate four models with varying complexity and fit these models to the data. We find that the most complex models that treat planets with significant gaseous envelopes, evaporated core planets, and intrinsically rocky planets as three separate populations are preferred by the data and provide the best fit to the observed distribution of Kepler planets. We use these models to calculate occurrence rates of planets in different regimes and to predict masses of Kepler planets, revealing the model-dependent nature of both. When using models with envelope mass loss to calculate η⊕, we find nearly an order of magnitude drop, indicating that many Earth-like planets discovered with Kepler may be evaporated cores which do not extrapolate out to higher orbital periods. This work provides a framework for higher-dimensional studies of planet occurrence and for using mixture models to incorporate different theoretical populations of planets.

Keywords: Bayesian statistics, Astrostatistics, Exoplanet astronomy, Exoplanet structure, Mixture model
Characterization of the Particle-induced Background of XMM-Newton EPIC-pn: Short- and Long-term Variability. The particle-induced background of X-ray observatories is produced by galactic cosmic ray (GCR) primary protons, electrons, and He ions. Events due to direct interaction with the detector are usually removed by onboard processing. The interactions of these primary particles with the detector environment produce secondary particles that mimic X-ray events from celestial sources, and are much more difficult to identify. The filter-wheel closed data from the XMM-Newton EPIC-pn camera in small window mode (SWM) contains both the X-ray-like background events, and the events due to direct interactions with the primary particles. From this data, we demonstrate that X-ray-like background events are spatially correlated with the primary particle interaction. This result can be used to further characterize and reduce the non-X-ray background in silicon-based X-ray detectors in current and future missions. We also show that spectrum and pattern fractions of secondary particle events are different from those produced by cosmic X-rays.

Keywords: Solar energetic particles, Astronomical instrumentation, Galactic cosmic rays, X-ray telescopes
Slip-back Mapping as a Tracker of Topological Changes in Evolving Magnetic Configurations. The topology of the coronal magnetic field has a strong impact on the properties of the solar corona and presumably on the origin of the slow solar wind. To advance our understanding of this impact, we revisit the concept of so-called slip-back mapping and adapt it to determine open, closed, and disconnected flux systems that are formed in the solar corona by magnetic reconnection during a given time interval. In particular, the method we developed allows us to describe magnetic flux transfer between open and closed flux regions via so-called interchange reconnection with an unprecedented level of detail. We illustrate the application of this method to the analysis of the global MHD evolution of the solar corona driven by idealized differential rotation of the photospheric plasma.

Keywords: Magnetohydrodynamics, Solar wind, Solar corona
A Massive Star's Dying Breaths: Pulsating Red Supergiants and Their Resulting Type IIP Supernovae. Massive stars undergo fundamental mode and first overtone radial pulsations with periods of 100-1000 days as red supergiants (RSGs). At large amplitudes, these pulsations substantially modify the outer envelope's density structure encountered by the outgoing shock wave from the eventual core collapse of these M &gt; 9 M_{⊙} stars. Using Modules for Experiments in Stellar Astrophysics (MESA), we model the effects of fundamental mode and first overtone pulsations in the RSG envelopes and the resulting Type IIP supernovae (SNe) using MESA+STELLA. We find that, in the case of fundamental mode pulsations, SN plateau observables, such as the luminosity at day 50, L50; time-integrated shock energy, ET; and plateau duration, tp, are consistent with radial scalings derived considering explosions of nonpulsating stars. Namely, most of the effect of the pulsation is consistent with the behavior expected for a star of a different size at the time of explosion. However, in the case of overtone pulsations, the Lagrangian displacement is not monotonic. Therefore, in such cases, excessively bright or faint SN emission at different times reflects the underdense or overdense structure of the emitting region near the SN photosphere.

Keywords: Red supergiant stars, Hydrodynamics, Type II supernovae, Massive stars, Radiative transfer, Stellar oscillations, Supernovae
Photodissociation Branching Ratios of <SUP>13</SUP>C<SUP>16</SUP>O in the Vacuum Ultraviolet Region from 102,745 to 106,360 cm<SUP>-1</SUP>. Direct branching ratio measurements for 13C16O are reported for the three lowest dissociation channels that produce C(3P)+O(3P), C(1D)+O(3P), and C(3P)+O(1D) in the vacuum ultraviolet (VUV) region from 102,745 cm-1 (97.33 nm) to 106,360 cm-1 (94.02 nm) and covering six 1Σ+ and six 1Π states. A time-slice velocity-map ion imaging apparatus with a tunable VUV laser source that is generated by the two-photon resonance-enhanced four-wave mixing technique is used to make these measurements. The results show that the substitution of 12C by 13C dramatically changes the photodissociation branching ratios into channels that produce C and O atoms in the excited 1D state for most of the absorption bands in the titled energy range. This isotope effect strongly depends on the specific rovibronic quantum states of CO that are being excited. The branching ratio data from the present study for 13C16O may significantly impact existing photochemical models because of the higher reactivity of the 1D states of the C and O atoms. In addition to this isotope effect, the rotational dependence of the branching ratios to high J' levels for several vibronic states has been determined. This provides useful information for unraveling the complicated predissociation dynamics of 13C16O.

Keywords: Photodissociation regions, Solar system, Interstellar medium
Real-time Flare Prediction Based on Distinctions between Flaring and Non-flaring Active Region Spectra. With machine learning entering into the awareness of the heliophysics community, solar flare prediction has become a topic of increased interest. Although machine-learning models have advanced with each successive publication, the input data has remained largely fixed on magnetic features. Despite this increased model complexity, results seem to indicate that photospheric magnetic field data alone may not be a wholly sufficient source of data for flare prediction. For the first time, we have extended the study of flare prediction to spectral data. In this work, we use Deep Neural Networks to monitor the changes of several features derived from the strong resonant Mg II h and k lines observed by the Interface Region Imaging Spectrograph. The features in descending order of predictive capability are: the triplet emission at 2798.77 Å, line core intensity, total continuum emission between the h and k line cores, the k/h ratio, line width, followed by several other line features such as asymmetry and line center. Regions that are about to flare generate spectra that are distinguishable from non-flaring active region spectra. Our algorithm can correctly identify pre-flare spectra approximately 35 minutes before the start of the flare, with an AUC of 86% and an accuracy, precision, and recall of 80%. The accuracy and AUC monotonically increase to 90% and 97%, respectively, as we move closer in time to the start of the flare. Our study indicates that spectral data alone can lead to good predictive models and should be considered an additional source of information alongside photospheric magnetograms.

Keywords: Solar flares, Neural networks, Solar flare spectra, Support vector machine, Dimensionality reduction
KMTNet Nearby Galaxy Survey II. Searching for Dwarf Galaxies in Deep and Wide-field Images of the NGC 1291 System. We present newly discovered dwarf galaxy candidates in deep and wide-field images of NGC 1291 obtained with the Korea Microlensing Telescope Network. We identify 15 dwarf galaxy candidates by visual inspection. Using imaging simulations, we demonstrate that the completeness rate of our detection is greater than 70% for the central surface-brightness value of μ0,R ≲ 26 mag arcsec-2 and for magnitudes MR ≲ -10 mag. The structural and photometric properties of the dwarf galaxy candidates appear to be broadly consistent with those of ordinary dwarf galaxies in nearby groups and clusters, with μ0,R ∼ 22.5 to 26.5 mag arcsec-2 and effective radii of 200 pc to 1 kpc. The dwarf galaxy candidates show a concentration toward NGC 1291 and tend to be redder the closer they are to the center, possibly indicating that they are associated with NGC 1291. The dwarf candidates presented in this paper appear to be bluer than those in denser environments, revealing that the quenching of star formation in dwarf galaxies is susceptible to the environment, while the morphology shaping is not.

Keywords: Dwarf galaxies