adsabs/SciX_UAT_keywords huggingface dataset:
Follow-up of Astrophysical Transients in Real Time with the IceCube Neutrino Observatory

In multi-messenger astronomy, rapid investigation of interesting transients is imperative. As an observatory with a 4π steradian field of view, and ∼99% uptime, the IceCube Neutrino Observatory is a unique facility to follow up transients, as well as to provide valuable insights for other observatories and inform their observational decisions. Since 2016, IceCube has been using low-latency data to rapidly respond to interesting astrophysical events reported by the multi-messenger observational community. Here, we describe the pipeline used to perform these followup analyses, and provide a summary of the 58 analyses performed as of July 2020. We find no significant signal in the first 58 analyses performed. The pipeline has helped inform various electromagnetic observation strategies, and has constrained neutrino emission from potential hadronic cosmic accelerators.

Keywords: neutrino astronomy; high energy astrophysics
The Effect of Environment on Galaxy Spiral Arms, Bars, Concentration, and Quenching

For a sample of 4378 nearby spiral and S0 galaxies, Yu & Ho used Fourier analysis of Sloan Digital Sky Survey images to show that the strengths of the spiral arms and the pitch angles of the arms are inversely correlated with central concentration. In the current study, we search for trends in the Yu & Ho spiral arm parameters with environment and specific star formation rate (sSFR). When comparing galaxies with similar concentrations, we do not find a significant difference in the arm strengths or pitch angles of spiral galaxies in clusters compared to field galaxies. When differences in concentration are taken into account, we also find no significant difference in the parameter f3 for cluster spirals compared to field spirals, where f3 is the normalized m = 3 Fourier amplitude. When concentration is held fixed, both arm strength and pitch angle are correlated with sSFR, but f3 is not. These relations support the suggestion by Davis et al. of a "fundamental plane" of spiral structure involving pitch angle, bulge stellar mass, and gas surface density. We discuss these results in terms of theories of spiral arm production and quenching in galaxies. To aid comparison with earlier studies based on Galaxy Zoo, we explore how the Yu & Ho parameters relate to similar parameters measured by Galaxy Zoo (i.e., f3 versus the number of arms, pitch angle versus winding parameter, and concentration versus bulge class).

Keywords: disk galaxies; galaxy clusters; galaxy environments; quenched galaxies
Observations of Particle Acceleration in Magnetic Reconnection-driven Turbulence

The Magnetospheric Multiscale Mission observes, in detail, charged particle heating and substantial nonthermal acceleration in a region of strong turbulence ( $| \delta {\boldsymbol{B}}| /| {\boldsymbol{B}}| \sim 1$ , where ${\boldsymbol{B}}$ is the magnetic field) that surrounds a magnetic reconnection X-line. Magnetic reconnection enables magnetic field annihilation in a volume that far exceeds that of the diffusion region. The formidable magnetic field annihilation breaks into strong, intermittent turbulence with magnetic field energy as the driver. The strong, intermittent turbulence appears to generate the necessary conditions for nonthermal acceleration. It creates intense, localized currents ( ${\boldsymbol{J}}$ ) and unusually large-amplitude electric fields ( ${\boldsymbol{E}}$ ). The combination of turbulence-generated ${\boldsymbol{E}}$ and ${\boldsymbol{J}}$ results in a significant net positive mean of ${\boldsymbol{J}}\cdot {\boldsymbol{E}}$ , which signifies particle energization. Ion and electron heating rates are such that they experience a fourfold increase from their initial temperature. Importantly, the strong turbulence also generates magnetic holes or depletions in $| {\boldsymbol{B}}| $ that can trap particles. Trapping considerably increases the dwell time of a subset of particles in the turbulent region, which results in significant nonthermal particle acceleration. The direct observation of strong turbulence that is enabled by magnetic reconnection with nonthermal particle acceleration has far-reaching implications, since turbulence in plasmas is pervasive and may occupy significant volumes of the interstellar medium and intergalactic space. For example, strong turbulence from magnetic field annihilation in the supernova nebulae may dominate large volumes. As such, this observed energization process could plausibly contribute to the supply and development of the cosmic-ray spectrum.

Keywords: space plasmas; plasma astrophysics; plasma physics
Transiting Exoplanet Yields for the Roman Galactic Bulge Time Domain Survey Predicted from Pixel-level Simulations

The Nancy Grace Roman Space Telescope (Roman) is NASA's next astrophysics flagship mission, expected to launch in late 2026. As one of Roman's core community science surveys, the Galactic Bulge Time Domain Survey (GBTDS) will collect photometric and astrometric data for over 100 million stars in the Galactic bulge in order to search for microlensing planets. To assess the potential with which Roman can detect exoplanets via transit, we developed and conducted pixel-level simulations of transiting planets in the GBTDS. From these simulations, we predict that Roman will find between ~60,000 and ~200,000 transiting planets-over an order of magnitude more planets than are currently known. While the majority of these planets will be giants (R p > 4R ⊕) on close-in orbits (a < 0.3 au), the yield also includes between ~7000 and ~12,000 small planets (R p < 4R ⊕). The yield for small planets depends sensitively on the observing cadence and season duration, with variations on the order of ~10%-20% for modest changes in either parameter, but is generally insensitive to the trade between surveyed area and cadence given constant slew/settle times. These predictions depend sensitively on the Milky Way's metallicity distribution function, highlighting an opportunity to significantly advance our understanding of exoplanet demographics, in particular across stellar populations and Galactic environments.

Keywords: planet hosting stars; exoplanets; transits
The Behavior of HgMn Stars in the Far-UV-Paper 15: HD 216494

The analysis of high resolution spectra of the HgMn star HD 216494 recorded by the SWP camera on board the International Ultraviolet Explorer reveals no variations of the far-ultraviolet flux of this star over 2 days in 1995 July. The far-ultraviolet resonance lines of Si II are strong absorbers in the spectrum of HD 216494. The resonance lines of Ga II, Ga III and Hg II, characteristic of classical HgMn stars, are also present in the mean SWP spectrum of HD 216494. The currently available TESS lightcurves of HD 216494 has a double wave structure with a period between two successive deep minima equal to 3.486 ± 0.054 days which could be the rotation period.

Keywords: chemically peculiar stars; mercury-manganese stars
The GIGANTES Data Set: Precision Cosmology from Voids in the Machine-learning Era

We present GIGANTES, the most extensive and realistic void catalog suite ever released-containing over 1 billion cosmic voids covering a volume larger than the observable universe, more than 20 TB of data, and created by running the void finder VIDE on QUIJOTE's halo simulations. The GIGANTES suite, spanning thousands of cosmological models, opens up the study of voids, answering compelling questions: Do voids carry unique cosmological information? How is this information correlated with galaxy information? Leveraging the large number of voids in the GIGANTES suite, our Fisher constraints demonstrate voids contain additional information, critically tightening constraints on cosmological parameters. We use traditional void summary statistics (void size function, void density profile) and the void autocorrelation function, which independently yields an error of 0.13 eV on ∑ m ν for a 1 h -3 Gpc3 simulation, without cosmic microwave background priors. Combining halos and voids we forecast an error of 0.09 eV from the same volume, representing a gain of 60% compared to halos alone. Extrapolating to next generation multi-Gpc3 surveys such as the Dark Energy Spectroscopic Instrument, Euclid, the Spectro-Photometer for the History of the Universe and Ices Explorer, and the Roman Space Telescope, we expect voids should yield an independent determination of neutrino mass. Crucially, GIGANTES is the first void catalog suite expressly built for intensive machine-learning exploration. We illustrate this by training a neural network to perform likelihood-free inference on the void size function, giving a ~20% constraint on Ωm. Cosmology problems provide an impetus to develop novel deep-learning techniques. With GIGANTES, machine learning gains an impressive data set, offering unique problems that will stimulate new techniques.

Keywords: n-body simulations; cosmology; large-scale structure of the universe; voids; cosmic web; computational astronomy; cosmological parameters; cosmological parameters from large-scale structure; cosmological neutrinos; astrostatistics
Surveying the Giant H II Regions of the Milky Way with SOFIA. VI. NGC 3603

We present our sixth set of results from our mid-infrared imaging survey of Milky Way Giant H II regions with our detailed analysis of NGC 3603, the most luminous giant H II (GH II) region in the Galaxy. We used imaging data from the FORCAST instrument on the Stratospheric Observatory For Infrared Astronomy (SOFIA) at 20 and 37 μm, which mapped the central ∼8.'5 × 8.'5 infrared-emitting area of NGC 3603 at a spatial resolution of ≲3″. Utilizing these SOFIA data in conjunction with multiwavelength observations from the near-infrared to radio, including Spitzer-IRAC and Herschel-PACS archival data, we investigate the physical nature of individual infrared sources and subcomponents within NGC 3603. For individual compact sources, we used the multiwavelength photometry data to construct spectral energy distributions (SEDs) and fit them with massive young stellar object (MYSO) SED models, and find 14 sources that are likely to be MYSOs. We also detect dust emission from the 3 massive proplyd candidates, as well as from the disk and outflow of the evolved blue supergiant, Sher 25. Utilizing multiwavelength data, we derived luminosity-to-mass ratio and virial parameters for the star-forming clumps within NGC 3603, estimating their relative ages and finding that NGC 3603 is an older GH II region overall, compared to our previously studied GH II regions. We discuss how NGC 3603, which we categorize as a cavity-type GH II region, exhibits a more modest number of MYSOs and molecular clumps when compared to the distributed-type GH II regions that share similar Lyman continuum photon rates.

Keywords: h ii regions; infrared sources; star formation; star forming regions; massive stars; infrared astronomy; young star clusters; protostars
Opacity-driven Convection and Variability in Accretion Disks around Supermassive Black Holes

We study the structure of accretion disks around supermassive black holes in the radial range of -100 gravitational radii, using a three-dimensional radiation magnetohydrodynamic simulation. For typical conditions in this region of active galactic nuclei (AGNs), the Rosseland mean opacity is expected to be larger than the electron scattering value. We show that the iron opacity bump causes the disk to be convectively unstable. Turbulence generated by convection puffs up the disk due to additional turbulent pressure support and enhances the local angular momentum transport. This also results in strong fluctuations in surface density and heating of the disk. The opacity drops with increasing temperature and convection is suppressed. The disk cools down and the whole process repeats again. This causes strong oscillations of the disk scale height and luminosity variations by more than a factor of ≈3-6 over a few years' timescale. Since the iron opacity bump will move to different locations of the disk for black holes with different masses and accretion rates, we suggest that this is a physical mechanism that can explain the variability of AGN with a wide range of amplitudes over a timescale of years to decades.

Keywords: accretion; black holes; magnetohydrodynamical simulations; quasars; supermassive black holes; active galactic nuclei; radiative magnetohydrodynamics; radiative transfer simulations
The Host Galaxies of Hybrid Morphology Radio Sources

Based on their differing radio morphologies, powerful radio galaxies can be separated into the Fanaroff-Riley I (FR I) and II (FR II) classes. Hybrid morphology radio sources (HyMoRS) contain morphologies consistent with each type of jet on either side: a powerful, highly relativistic FR I-like jet terminating in a hotspot on one side and an FR I-like plume on the other. HyMoRS present a unique opportunity to study the conditions that give rise to the dichotomy. Using host galaxy properties, we conduct the first multiwavelength investigation into whether orientation can explain HyMoRS morphology. Through optical spectroscopy and mid-infrared photometry, we analyze the emission characteristics, and evaluate the broad characteristics of five HyMoRS host galaxies at intermediate redshifts (0.4 < z < 1.5). The HyMoRS host galaxies in our sample have properties consistent with typical host galaxies of FR II sources, suggesting that the observed hybrid morphologies may be caused by a dense, cluster-like environment bending FR II jets combined with a favorable orientation that can make one side appear similar to an FR I jet. Our results thus support the hypothesis that HyMoRS are mainly caused by environment and orientation.

Keywords: active galaxies; early-type galaxies; emission line galaxies; fanaroff-riley radio galaxies; galaxy clusters; galaxy environments; galaxy evolution; ionization; radio galaxies; spectroscopy
Meta-analysis of Photometric and Asteroseismic Measurements of Stellar Rotation Periods: The Lomb-Scargle Periodogram, Autocorrelation Function, and Wavelet and Rotational Splitting Analysis for 92 Kepler Asteroseismic Targets

We perform intensity variability analyses (photometric analyses: the Lomb-Scargle periodogram, autocorrelation, and wavelet) and asteroseismic analysis of 92 Kepler solar-like main-sequence stars to understand the reliability of the measured stellar rotation periods. We focus on the 70 stars without reported stellar companions, and classify them into four groups according to the quarter-to-quarter variance of the Lomb-Scargle period and the precision of the asteroseismic period. We present detailed individual comparison among photometric and asteroseismic constraints for these stars. We find that most of our targets exhibit significant quarter-to-quarter variances in the photometric periods, suggesting that the photometrically estimated period should be regarded as a simplified characterization of the true stellar rotation period, especially under the presence of the latitudinal differential rotation. On the other hand, there are a fraction of stars with a relatively small quarter-to-quarter variance in the photometric periods, most of which have consistent values for asteroseismically and photometrically estimated rotation periods. We also identify over 10 stars whose photometric and asteroseismic periods significantly disagree, which would be potentially interesting targets for further individual investigations.

Keywords: stellar rotation; stellar photometry; starspots; stellar activity; astronomy data analysis; solar analogs; asteroseismology
C/O Ratios and the Formation of Wide-separation Exoplanets

The gas and solid-state C/O ratios provide context to potentially link the atmospheric composition of planets to that of the natal disk. We provide a synthesis of extant estimates of the gaseous C/O and C/H ratios in planet-forming disks obtained primarily through analysis of Atacama Large Millimeter/submillimeter Array observations. These estimates are compared to atmospheric abundances of wide-separation (>10 au) gas giants. The resolved disk gas C/O ratios, from seven systems, generally exhibit C/O ≥ 1 with subsolar, or depleted, carbon content. In contrast, wide-separation gas giants have atmospheric C/O ratios that cluster near or slightly above the presumed stellar value with a range of elemental C/H. From the existing disk composition, we infer that the solid-state millimeter/centimeter-sized pebbles have a total C/O ratio (solid cores and ices) that is solar (stellar) in content. We explore simple models that reconstruct the exoplanet atmospheric composition from the disk, while accounting for silicate cloud formation in the planet atmosphere. If wide-separation planets formed via the core-accretion mechanism, they must acquire their metals from pebble or planetesimal accretion. Further, the dispersion in giant planet C/H content is best matched by a disk composition with modest and variable factors of carbon depletion. An origin of the wide-separation gas giants via gravitational instability cannot be ruled out, as stellar C/O ratios should natively form in this scenario. However, the variation in planet metallicity with a stellar C/O ratio potentially presents challenges to these models.

Keywords: exoplanet atmospheric composition; exoplanet formation; protoplanetary disks; circumstellar disks
Super-Earths and Sub-Neptunes Are Insensitive to Stellar Metallicity

Kepler planets (including super-Earths and sub-Neptunes, from 1-4 Earth radii) are likely formed before the gaseous protoplanetary disks have dissipated, as are the Jovian planets. If the metal content in these disks resembles that in the host stars, one might expect Kepler planets to occur more frequently, and to be more massive, around metal-rich stars. Contrary to these expectations, we find that the radii of Kepler planets (a proxy for mass) are independent of host metallicity. Previous claims that larger planets prefer more metal-rich stars can be adequately explained by the combined facts that more massive stars tend to host bigger planets, and that more massive stars are also more metal-rich in the Kepler sample. We interpret this independence as that the mass of a Kepler planet is not determined by the availability of solids, but is instead regulated by an as yet unknown process. Moreover, we find that the occurrence rates of Kepler planets rise only weakly with stellar metallicity, a trend that is further flattened when the influence of close stellar binaries is accounted for. We explain this weak dependence, in contrast to the strong dependence exhibited by Jovian planets, using a phenomenological model, wherein the masses of protoplanetary disks have a much larger spread than the spread in stellar metallicity, and wherein the formation of Jovian planets requires disks that contain some 5 times more solids than that needed to form Kepler planets. This model predicts that stars more metal-poor than half-solar should rarely host any Kepler planets.

Keywords: star-planet interactions; mini neptunes; super earths; exoplanet formation
Estimating the Contribution of Foreground Halos to the FRB 180924 Dispersion Measure

Fast radio burst (FRB) dispersion measures (DMs) record the presence of ionized baryons that are otherwise invisible to other techniques enabling resolution of the matter distribution in the cosmic web. In this work, we aim to estimate the contribution to FRB 180924 DM from foreground galactic halos. Localized by ASKAP to a massive galaxy, this sightline is notable for an estimated cosmic web contribution to the DM (DMcosmic =220 pc cm-3), which is less than the average value at the host redshift (z = 0.3216) estimated from the Macquart relation (280 pc cm-3). In the favored models of the cosmic web, this suggests few intersections with foreground halos at small impact parameters (≲100 kpc). To test this hypothesis, we carried out spectroscopic observations of the field galaxies within ~1' of the sightline with VLT/MUSE and Keck/LRIS. Furthermore, we developed a probabilistic methodology that leverages photometric redshifts derived from wide-field DES and WISE imaging. We conclude that there is no galactic halo that closely intersects the sightline and also that the net DM contribution from halos DMhalos < 45 pc cm-3 (95% c.l.). This value is lower than the DMhalos estimated from an "average" sightline (121 pc cm-3) using the Planck ΛCDM model and the Aemulus halo mass function and reasonably explains its low DMcosmic value. We conclude that FRB 180924 represents the predicted majority of sightlines in the universe with no proximate foreground galactic halos. Our framework lays the foundation for a comprehensive analysis of FRB fields in the near future.

Keywords: galaxy dark matter halos; cosmology; quasar absorption line spectroscopy; radio transient sources; extragalactic astronomy
Electromagnetic Counterparts Powered by Kicked Remnants of Black Hole Binary Mergers in AGN Disks

The disk of an active galactic nucleus (AGN) is widely regarded as a prominent formation channel of binary black hole (BBH) mergers that can be detected through gravitational waves (GWs). Besides, the presence of dense environmental gas offers the potential for an embedded BBH merger to produce electromagnetic (EM) counterparts. In this paper, we investigate EM emission powered by the kicked remnant of a BBH merger occurring within the AGN disk. The remnant BH will launch a jet via the accretion of a magnetized medium as it traverses the disk. The resulting jet will decelerate and dissipate energy into a lateral cocoon as it propagates. We explore three radiation mechanisms of the jet–cocoon system—jet breakout emission, disk cocoon cooling emission, and jet cocoon cooling emission—and find that the jet cocoon cooling emission is likely to be detected in its own frequency bands. We predict a soft X-ray transient, lasting for O(103) s, to serve as an EM counterpart, of which the time delay O(10) days after the GW trigger contributes to follow-up observations. Consequently, BBH mergers in the AGN disk represent a novel multimessenger source. In the future, enhanced precision in measuring and localizing GWs, coupled with diligent searches for such associated EM signals, will effectively validate or restrict the origin of BBH mergers in the AGN disk.

Keywords: active galactic nuclei; accretion; black holes; gravitational wave sources; jets
New Open-cluster Candidates Found in the Galactic Disk Using Gaia DR2/EDR3 Data

We report 541 new open-cluster candidates in Gaia EDR3 through revisiting the cluster results from an earlier analysis of Gaia DR2, which revealed nearly 1000 open-cluster candidates in the solar neighborhood (mostly d <3 kpc) residing at Galactic latitudes ∣b∣ < 20°. A subsequent comparison with lists of known clusters shows a large increase of the cluster samples within 2 kpc from the Sun. We assign membership probabilities to the stars through the open-source pyUPMASK algorithm, and also estimate the physical parameters through isochrone fitting for each candidate. Most of the new candidates show small total-proper-motion dispersions and clear features in the color-magnitude diagrams. Besides, the metallicity gradient of the new candidates is consistent with those found in the literature. The cluster parameters and member stars are available at CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via https://cdsarc.unistra.fr/viz-bin/cat/J/ApJS/260/8. The discovery of these new objects shows that the open-cluster samples in Gaia data is still not complete, and more discoveries are expected in future research.

Keywords: open star clusters; star clusters