adsabs/SciX_UAT_keywords huggingface dataset:
Spectroastrometry and Reverberation Mapping: The Mass and Geometric Distance of the Supermassive Black Hole in the Quasar 3C 273

The quasar 3C 273 has been observed with infrared spectroastrometry (SA) of the broad Paα line and optical reverberation mapping (RM) of the broad Hβ line. SA delivers information about the angular size and structure of the Paα broad-line region (BLR), while RM delivers information about the physical size and structure of the Hβ BLR. Based on the fact that the two BLRs share the mass of the supermassive black hole (SMBH) and viewing inclination, a combination of SA and velocity-resolved RM (SARM) thereby allows us to simultaneously determine the SMBH mass and geometric distance through dynamically modeling the two BLRs. We construct a suite of dynamical models with different geometric configurations and apply a Bayesian approach to obtain the parameter inferences. Overall the obtained masses and distances are insensitive to specific BLR configurations but more or less depend on parameterizations of the vertical distributions. The most probable model, chosen in light of the Bayes factor, yields an angular-size distance $\mathrm{log}({D}_{{\rm{A}}}/\mathrm{Mpc})={2.83}_{-0.28}^{+0.32}$ and an SMBH mass $\mathrm{log}({M}_{\bullet }/{M}_{\odot })={9.06}_{-0.27}^{+0.21}$ , which agree with the relationships between SMBH masses and bulge properties. The BLRs have an inclination of ${5}_{-1}^{+1}$ degrees, consistent with that of the large-scale jet in 3C 273. Our approach reinforces the capability of SARM analysis to measure SMBH masses and distances of active galactic nuclei and quasars even though SA and RM observations are undertaken with different emission lines and/or in different periods.

Keywords: active galaxies; quasars; supermassive black holes; reverberation mapping; astrometry
Elemental Abundances in M31: Iron and Alpha Element Abundances in M31's Outer Halo

We present [Fe/H] and [α/Fe] abundances, derived using spectral synthesis techniques, for stars in M31's outer stellar halo. The 21 [Fe/H] measurements and 7 [α/Fe] measurements are drawn from fields ranging from 43 to 165 kpc in projected distance from M31. We combine our measurements with existing literature measurements, and compare the resulting sample of 23 stars with [Fe/H] and 9 stars with [α/Fe] measurements in M31's outer halo with [α/Fe] and [Fe/H] measurements, also derived from spectral synthesis, in M31's inner stellar halo (r < 26 kpc) and dSph galaxies. The stars in M31's outer halo have [α/Fe] patterns that are consistent with the largest of M31's dSph satellites (And I and And VII). These abundances provide tentative evidence that the [α/Fe] abundances of stars in M31's outer halo are more similar to the abundances of Milky Way halo stars than to the abundances of stars in M31's inner halo. We also compare the spectral synthesis-based [Fe/H] measurements of stars in M31's halo with previous photometric [Fe/H] estimates, as a function of projected distance from M31. The spectral synthesis-based [Fe/H] measurements are consistent with a large-scale metallicity gradient previously observed in M31's stellar halo to projected distances as large as 100 kpc. * The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

Keywords: galaxy stellar halos; local group; galaxies; andromeda galaxy; stellar abundances
A New Sample of Warm Extreme Debris Disks from the ALLWISE Catalog

Extreme debris disks (EDDs) are rare systems with peculiarly large amounts of warm dust that may stem from recent giant impacts between planetary embryos during the final phases of terrestrial planet growth. Here we report on the identification and characterization of six new EDDs. These disks surround F5-G9 type main-sequence stars with ages >100 Myr, have dust temperatures higher than 300 K, and fractional luminosities between 0.01 and 0.07. Using time-domain photometric data at 3.4 and 4.6 μm from the WISE all-sky surveys, we conclude that four of these disks exhibited variable mid-infrared (IR) emission between 2010 and 2019. Analyzing the sample of all known EDDs, now expanded to 17 objects, we find that 14 of them showed changes at 3-5 μm over the past decade, suggesting that mid-IR variability is an inherent characteristic of EDDs. We also report that wide-orbit pairs are significantly more common in EDD systems than in the normal stellar population. While current models of rocky planet formation predict that the majority of giant collisions occur in the first 100 Myr, we find that the sample of EDDs is dominated by systems older than this age. This raises the possibility that the era of giant impacts may be longer than we think, or that some other mechanism(s) can also produce EDDs. We examine a scenario where the observed warm dust stems from the disruption and/or collisions of comets delivered from an outer reservoir into the inner regions, and explore what role the wide companions could play in this process.

Keywords: circumstellar disks; debris disks; exozodiacal dust; extrasolar rocky planets; infrared excess; time domain astronomy
A Partial Disintegration of Active Centaur/Comet P/2020 MK4?

Centaur P/2020 MK4 (a = 6.19 au, e = 0.011) was discovered in 2020 and quickly brightened to V ~ 18.5. As of early 2022 November, no astrometric observations had been reported in 2021 or 2022. The object should have been easily found had it retained its 2020 absolute magnitude. We find that P/2020 MK4 now appears as an ~10″ wide low surface brightness coma, with a faint (r ~ 24.9) point-like source. The rates of brightening and fading of P/2020 MK4 are both much slower than the larger Centaur 29P/Schwassmann-Wachmann 1, which is on a similar orbit. Perhaps the image morphology and unusual brightening and fading of P/2020 MK4 were due to a partial disintegration event.

Keywords: centaur group; comets; comae
Nebular C IV λ1550 Imaging of the Metal-poor Starburst Mrk 71: Direct Evidence of Catastrophic Cooling

We use the Hubble Space Telescope Advanced Camera for Surveys to obtain the first spatially resolved, nebular imaging in the light of C IV λ λ1548, 1551 by using the F150LP and F165LP filters. These observations of the local starburst Mrk 71 in NGC 2366 show emission apparently originating within the interior cavity around the dominant super star cluster (SSC), Knot A. Together with imaging in He II λ4686 and supporting Space Telescope Imaging Spectrograph far-ultraviolet spectroscopy, the morphology and intensity of the C IV nebular surface brightness and the C IV/He II ratio map provide direct evidence that the mechanical feedback is likely dominated by catastrophic radiative cooling, which strongly disrupts adiabatic superbubble evolution. The implied extreme mass loading and low kinetic efficiency of the cluster wind are reasonably consistent with the wind energy budget, which is probably enhanced by radiation pressure. In contrast, the Knot B SSC lies within a well-defined superbubble with associated soft X-rays and He II λ1640 emission, which are signatures of adiabatic, energy-driven feedback from a supernova-driven outflow. This system lacks clear evidence of C IV from the limb-brightened shell, as expected for this model, but the observations may not be deep enough to confirm its presence. We also detect a small C IV-emitting object that is likely an embedded compact H II region. Its C IV emission may indicate the presence of very massive stars (>100 M ⊙) or strongly pressure-confined stellar feedback.

Keywords: starburst galaxies; galaxy winds; galaxy evolution; emission line galaxies; stellar feedback; young massive clusters; superbubbles; h ii regions; ultraviolet photometry; direct imaging
Searching for Hypercompact Star Clusters in the Milky Way Using LAMOST and Gaia

During the early merger of the Milky Way, intermediate-mass black holes (BHs) in merged dwarf galaxies may have been ejected from the center of their host galaxies due to gravitational waves, carrying some central stars along. This process can lead to the formation of hypercompact star clusters, potentially hosting BHs in the mass range of 104–105 solar masses. These clusters are crucial targets for identifying and investigating intermediate-mass BHs. However, no hypercompact star clusters in the Milky Way have been identified so far. In this paper, taking advantage of the high spatial resolution power of Gaia, we used data from Gaia Early Data Release (EDR) 3 and Large-Area Multi-Object Fiber Optic Spectroscopic Telescope Data Release 7, along with additional data from Pan-STARRS and the Sloan Digital Sky Survey, to conduct an initial screening of 6,138,049 sources using various parameters of Gaia EDR3. A total of 4786 sources were selected for in-depth analysis. Each of these sources was meticulously scrutinized by examining their images, spectra, and nearby celestial objects to exclude various false positives, such as contaminations, galaxies, wide binaries, or wrong matches. We finally identified one likely hypercompact star cluster candidate in the Milky Way, laying the foundation for further high-resolution imaging and spectral verification.

Keywords: star clusters; astronomy data analysis; surveys; intermediate-mass black holes
A JWST Near- and Mid-infrared Nebular Spectrum of the Type Ia Supernova 2021aefx

We present JWST near-infrared (NIR) and mid-infrared (MIR) spectroscopic observations of the nearby normal Type Ia supernova (SN) SN 2021aefx in the nebular phase at +255 days past maximum light. Our Near Infrared Spectrograph (NIRSpec) and Mid Infrared Instrument observations, combined with ground-based optical data from the South African Large Telescope, constitute the first complete optical+NIR+MIR nebular SN Ia spectrum covering 0.3-14 μm. This spectrum unveils the previously unobserved 2.5-5 μm region, revealing strong nebular iron and stable nickel emission, indicative of high-density burning that can constrain the progenitor mass. The data show a significant improvement in sensitivity and resolution compared to previous Spitzer MIR data. We identify numerous NIR and MIR nebular emission lines from iron-group elements as well as lines from the intermediate-mass element argon. The argon lines extend to higher velocities than the iron-group elements, suggesting stratified ejecta that are a hallmark of delayed-detonation or double-detonation SN Ia models. We present fits to simple geometric line profiles to features beyond 1.2 μm and find that most lines are consistent with Gaussian or spherical emission distributions, while the [Ar III] 8.99 μm line has a distinctively flat-topped profile indicating a thick spherical shell of emission. Using our line profile fits, we investigate the emissivity structure of SN 2021aefx and measure kinematic properties. Continued observations of SN 2021aefx and other SNe Ia with JWST will be transformative to the study of SN Ia composition, ionization structure, density, and temperature, and will provide important constraints on SN Ia progenitor and explosion models.

Keywords: supernovae; type ia supernovae; white dwarf stars
Precise Age for the Binary Star System 12 Com in the Coma Berenices Cluster

We present measurements of the interferometrically resolved binary star system 12 Com and the single giant star 31 Com in the cluster Coma Berenices. 12 Com is a double-lined spectroscopic binary system consisting of a G7 giant and an A3 dwarf at the cluster turnoff. Using an extensive radial velocity data set and interferometric measurements from the Palomar Testbed Interferometer and the Center for High Angular Resolution Astronomy array, we measured masses M 1 = 2.64 ± 0.07M ⊙ and M 2 = 2.10 ± 0.03M ⊙. Interferometry also allows us to resolve the giant and measure its size as R 1 = 9.12 ± 0.12 ± 0.01R ⊙. With the measured masses and radii, we find an age of 533 ± 41 ± 42 Myr. For comparison, we measure the radius of 31 Com to be 8.36 ± 0.15 R ⊙. Based on the photometry and radius measurements, 12 Com A is likely the most evolved bright star in the cluster, large enough to be in the red giant phase, but too small to have core helium burning. Simultaneous knowledge of 12 Com A's mass and photometry puts strong constraints on convective core overshooting during the main-sequence phase, which in turn reduces systematic uncertainties in the age. Increased precision in measuring this system also improves our knowledge of the progenitor of the cluster white dwarf WD1216+260.

Keywords: stellar ages; interferometric binary stars; white dwarf stars; stellar evolution; open star clusters; spectroscopic binary stars
The Solar Disk at High Energies

High energy cosmic rays illuminate the Sun and produce an image that could be observed in up to five different channels: a cosmic-ray shadow (whose energy dependence has been studied by HAWC); a gamma-ray flux (observed at E ≤ 200 GeV by Fermi-LAT); a muon shadow (detected by ANTARES and IceCube); a neutron flux (undetected, as there are no hadronic calorimeters in space); a flux of high energy neutrinos. Since these signals are correlated, the ones already observed can be used to reduce the uncertainty in the still undetected ones. Here we define a simple setup that uses the Fermi-LAT and HAWC observations to imply very definite fluxes of neutrons and neutrinos from the solar disk. In particular, we provide a fit of the neutrino flux at 10 GeV-10 TeV that includes its dependence on the zenith angle and on the period of the solar cycle. This flux represents a neutrino floor in indirect dark matter searches. We show that in some benchmark models the current bounds on the dark matter-nucleon cross section push the solar signal below this neutrino floor.

Keywords: cosmic rays; gamma-rays; neutrino telescopes; solar physics
The Swansong of the Galactic Center Source X7: An Extreme Example of Tidal Evolution near the Supermassive Black Hole

We present two decades of new high-angular-resolution near-infrared data from the W. M. Keck Observatory that reveal extreme evolution in X7, an elongated dust and gas feature, presently located half an arcsecond from the Galactic Center supermassive black hole. With both spectro-imaging observations of Br-γ line emission and Lp (3.8 μm) imaging data, we provide the first estimate of its orbital parameters and quantitative characterization of the evolution of its morphology and mass. We find that the leading edge of X7 appears to be on a mildly eccentric (e ~ 0.3), relatively short-period (170 yr) orbit and is headed toward periapse passage, estimated to occur in ~2036. Furthermore, our kinematic measurements rule out the earlier suggestion that X7 is associated with the stellar source S0-73 or with any other point source that has overlapped with X7 during our monitoring period. Over the course of our observations, X7 has (1) become more elongated, with a current length-to-width ratio of 9, (2) maintained a very consistent long-axis orientation (position angle of 50°), (3) inverted its radial velocity differential from tip to tail from -50 to +80 km s-1, and (4) sustained its total brightness (12.8 Lp magnitudes at the leading edge) and color temperature (425 K), which suggest a constant mass of ~50 M Earth. We present a simple model showing that these results are compatible with the expected effect of tidal forces exerted on it by the central black hole, and we propose that X7 is the gas and dust recently ejected from a grazing collision in a binary system.

Keywords: galactic center; tidal interaction; supermassive black holes; interstellar medium
TKS X: Confirmation of TOI-1444b and a Comparative Analysis of the Ultra-short-period Planets with Hot Neptunes

We report the discovery of TOI-1444b, a 1.4 R⊕ super-Earth on a 0.47 day orbit around a Sun-like star discovered by TESS. Precise radial velocities from Keck/HIRES confirmed the planet and constrained the mass to be 3.87 ± 0.71M⊕. The RV data set also indicates a possible nontransiting, 16 day planet (11.8 ± 2.9M⊕). We report a tentative detection of phase-curve variation and a secondary eclipse of TOI-1444b in the TESS bandpass. TOI-1444b joins the growing sample of 17 ultra-short-period planets (USPs) with well-measured masses and sizes, most of which are compatible with an Earth-like composition. We take this opportunity to examine the expanding sample of ultra-short-period planets (<2R⊕) and contrast them with the newly discovered sub-day ultrahot Neptunes (>3R⊕, >2000F⊕ TOI-849 b, LTT9779 b, and K2-100). We find that (1) USPs have predominately Earth-like compositions with inferred iron core mass fractions of 0.32 ± 0.04 and have masses below the threshold of runaway accretion (~10M⊕), while ultrahot Neptunes are above the threshold and have H/He or other volatile envelopes. (2) USPs are almost always found in multi-planet systems consistent with a secular interaction formation scenario; ultrahot Neptunes (Porb ≲1 day) tend to be "lonely," similar to longer-period hot Neptunes (Porb1-10 days) and hot Jupiters. (3) USPs occur around solar-metallicity stars while hot Neptunes prefer higher metallicity hosts. (4) In all these respects, ultrahot Neptunes show more resemblance to hot Jupiters than the smaller USP planets, although ultrahot Neptunes are rarer than both USPs and hot Jupiters by 1-2 orders of magnitude.

Keywords: exoplanets; super earths; extrasolar rocky planets
Lunar Gravitational-wave Antenna

Monitoring of vibrational eigenmodes of an elastic body excited by gravitational waves was one of the first concepts proposed for the detection of gravitational waves. At laboratory scale, these experiments became known as resonant bar detectors first developed by Joseph Weber in the 1960s. Due to the dimensions of these bars, the targeted signal frequencies were in the kHz range. Weber also pointed out that monitoring of vibrations of Earth or the Moon could reveal gravitational waves in the mHz band. His Lunar Surface Gravimeter experiment deployed on the Moon by the Apollo 17 crew had a technical failure, which greatly reduced the science scope of the experiment. In this article, we revisit the idea and propose a Lunar Gravitational-Wave Antenna (LGWA). We find that LGWA could become an important partner observatory for joint observations with the space-borne, laser-interferometric detector LISA and at the same time contribute an independent science case due to LGWA's unique features. Technical challenges need to be overcome for the deployment of the experiment, and development of inertial vibration sensor technology lays out a future path for this exciting detector concept.

Keywords: gravitational waves; lunar science
Astrophysical Properties of 600 Bona Fide Single Stars in the Hyades Open Cluster

The determination of the astrophysical properties of stars remains challenging and frequently relies on the application of stellar models. Stellar sequences in nearby open clusters provide some of the best means to test and calibrate stellar evolutionary models and isochrones and to use these models to assign astrophysical properties consistently to a large sample of stars. We aim at updating the single-star sequence of the members of the Hyades cluster, identifying the best-fitting isochrones, and determining the astrophysical properties of the stars. The Gaia Catalog of Nearby Stars provides a comprehensive sample of high-probability members of the Hyades cluster. We apply a multistep method to flag photometric outliers and to identify bona fide single stars and likely binary and multiple systems. The single stars define a tight sequence, which in the mass range 0.12-2.2 M ⊙ is well fitted by PARSEC isochrones for a supersolar metallicity of [M/H] = +0.18 ± 0.03 and an age of 775 ± 25 Myr. The isochrones enable us to assign mass, effective temperature, luminosity, and surface gravity to each of the 600 bona fide single main-sequence stars. The observed sequence validates the PARSEC isochrones. The derived stellar properties can serve as benchmarks for atmospheric and evolutionary models and for all-sky catalogs of stellar astrophysical properties. The stellar properties are also relevant for studies of exoplanet properties among Hyades exoplanet hosts.

Keywords: open star clusters; stellar evolution; stellar dynamics; stellar colors; stellar effective temperatures; stellar luminosities; stellar masses; young star clusters; stellar abundances; stellar properties; stellar ages; stellar types
Free-floating Planet Mass Function from MOA-II 9 yr Survey toward the Galactic Bulge

We present the first measurement of the mass function of free-floating planets (FFPs), or very wide orbit planets down to an Earth mass, from the MOA-II microlensing survey in 2006-2014. Six events are likely to be due to planets with Einstein radius crossing times t E < 0.5 days, and the shortest has t E = 0.057 ± 0.016 days and an angular Einstein radius of θ E = 0.90 ± 0.14 μas. We measure the detection efficiency depending on both t E and θ E with image-level simulations for the first time. These short events are well modeled by a power-law mass function, ${{dN}}_{4}/d\mathrm{log}M={({2.18}_{-1.40}^{+0.52})\times (M/8\,{M}_{\oplus })}^{-{\alpha }_{4}}$ dex-1 star-1 with ${\alpha }_{4}={0.96}_{-0.27}^{+0.47}$ for M/M ⊙ < 0.02. This implies a total of $f={21}_{-13}^{+23}$ FFPs or very wide orbit planets of mass 0.33 < M/M ⊕ < 6660 per star, with a total mass of ${80}_{-47}^{+73}{M}_{\oplus }$ star-1. The number of FFPs is ${19}_{-13}^{+23}$ times the number of planets in wide orbits (beyond the snow line), while the total masses are of the same order. This suggests that the FFPs have been ejected from bound planetary systems that may have had an initial mass function with a power-law index of α ~ 0.9, which would imply a total mass of ${171}_{-52}^{+80}{M}_{\oplus }$ star-1. This model predicts that Roman Space Telescope will detect ${988}_{-566}^{+1848}$ FFPs with masses down to that of Mars (including ${575}_{-424}^{+1733}$ with 0.1 ≤ M/M ⊕ ≤ 1). The Sumi et al. large Jupiter-mass FFP population is excluded.

Keywords: gravitational microlensing; gravitational microlensing exoplanet detection; free floating planets; exoplanet astronomy; galactic bulge
The Active Galactic Nuclei in the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX). II. Luminosity Function

We present the Lyα emission line luminosity function (LF) of the active galactic nuclei (AGN) in the first release of the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX) AGN catalog. The AGN are selected either by emission line pairs characteristic of AGN or by a single broad emission line, free of any photometric preselections (magnitude/color/morphology). The sample consists of 2346 AGN spanning 1.88 < z < 3.53, covering an effective area of 30.61 deg2. Approximately 2.6% of the HETDEX AGN are not detected at >5σ confidence at r ~ 26 in the deepest r-band images we have searched. The Lyα line luminosity ranges from ~1042.3 to 1045.9 erg s-1. Our Lyα LF shows a turnover luminosity with opposite slopes on the bright end and the faint end: The space density is highest at ${L}_{\text{Ly}{\text{\unicode{x003B1}}}}^{\ast }={10}^{43.4}$ erg s-1. We explore the evolution of the AGN LF over a broader redshift range (0.8 < z < 3); constructing the rest-frame ultraviolet (UV) LF with the 1450 Å monochromatic luminosity of the power-law component of the continuum (M1450) from M 1450 ~ -18 to -27.5. We divide the sample into three redshift bins (z ~ 1.5, 2.1, and 2.6). In all three redshift bins, our UV LFs indicate that the space density of AGN is highest at the turnover luminosity ${M}_{1450}^{* }$ with opposite slopes on the bright end and the faint end. The M 1450 LFs in the three redshift bins can be well fit with a luminosity evolution and density evolution model: the turnover luminosity ( ${M}_{1450}^{* }$ ) increases, and the turnover density (Φ*) decreases with increasing redshift.

Keywords: active galactic nuclei; luminosity function