adsabs/SciX_UAT_keywords huggingface dataset:
The High-energy Spectrum of the Nearby Planet-hosting Inactive Mid-M Dwarf LHS 3844

To fully characterize the atmospheres, or lack thereof, of terrestrial exoplanets, we must include the high-energy environments provided by their host stars. The nearby mid-M dwarf LHS 3844 hosts a terrestrial world that lacks a substantial atmosphere. We present a time-series UV spectrum of LHS 3844 from 1131 to 3215 Å captured by HST/COS. We detect one flare in the FUV that has an absolute energy of 8.96 ± 0.77 × 1028 erg and an equivalent duration of 355 ± 31 s. We extract the flare and quiescent UV spectra separately. For each spectrum, we estimate the Lyα flux using correlations between UV line strengths. We use Swift-XRT to place an upper limit on the soft X-ray flux and construct a differential emission model to estimate flux that is obscured by the interstellar medium. We compare the differential emission model flux estimates in the XUV to other methods that rely on scaling from the Lyα, Si iv, and N v lines in the UV. The XUV, FUV, and NUV flux of LHS 3844 relative to its bolometric luminosity is log10(Lband/LBol) =-3.65, -4.16, and -4.48, respectively, for the quiescent state. These values agree with trends in high-energy flux as a function of stellar effective temperature found by the MUSCLES survey for a sample of early-M dwarfs. Many of the most spectroscopically accessible terrestrial exoplanets orbit inactive mid-to-late M dwarfs like LHS 3844. Measurements of M dwarf high-energy spectra are preferable for exoplanet characterization but are not always possible. The spectrum of LHS 3844 is a useful proxy for the current radiation environment for these worlds.

Keywords: ultraviolet astronomy; m dwarf stars; exoplanet atmospheres; stellar flares; hubble space telescope; ultraviolet observatories; space observatories
Retrieval of the d/sdL7+T7.5p Binary SDSS J1416+1348AB

We present the distance-calibrated spectral energy distribution (SED) of the d/sdL7 SDSS J14162408+1348263A (J1416A) and an updated SED for SDSS J14162408+1348263B (J1416B). We also present the first retrieval analysis of J1416A using the Brewster retrieval code base and the second retrieval of J1416B. We find that the primary is best fit by a nongray cloud opacity with a power-law wavelength dependence but is indistinguishable between the type of cloud parameterization. J1416B is best fit by a cloud-free model, consistent with the results from Line et al. Most fundamental parameters derived via SEDs and retrievals are consistent within 1σ for both J1416A and J1416B. The exceptions include the radius of J1416A, where the retrieved radius is smaller than the evolutionary model-based radius from the SED for the deck cloud model, and the bolometric luminosity, which is consistent within 2.5σ for both cloud models. The pair's metallicity and carbon-to-oxygen ratio point toward formation and evolution as a system. By comparing the retrieved alkali abundances while using two opacity models, we are able to evaluate how the opacities behave for the L and T dwarf. Lastly, we find that relatively small changes in composition can drive major observable differences for lower-temperature objects.

Keywords: brown dwarfs; l subdwarfs; t subdwarfs; fundamental parameters of stars
Radial Velocity Photon Limits for the Dwarf Stars of Spectral Classes F-M

The determination of extrasolar planet masses with the radial velocity (RV) technique requires spectroscopic Doppler information from the planet's host star, which varies with stellar brightness and temperature. We analyze the Doppler information in spectra from dwarfs of spectral types F-M utilizing empirical information from HARPS and CARMENES data and model spectra. We revisit the question of whether optical or near-infrared instruments are more efficient for RV observations in low-mass stars, and we come to the conclusion that an optical setup (BVR bands) is more efficient than a near-infrared one (YJHK) in dwarf stars hotter than 3200 K. We publish a catalog of 46,480 well-studied F-M dwarfs in the solar neighborhood, and we compare its distribution to more than 1 million stars from Gaia DR2. For all stars, we estimate the RV photon noise achievable in typical observations under the assumption of no activity jitter and slow rotation. We find that with an ESPRESSO-like instrument at an 8 m telescope, a photon noise limit of 10 cm s-1 or lower can be reached in more than 280 stars in a 5 minute observation. At 4 m telescopes, a photon noise limit of 1 m s-1 can be reached in a 10 minute exposure in approximately 10,000 predominantly Sun-like stars with a HARPS-like (optical) instrument. The same applies to ∼3000 stars for a red optical setup that covers the R and I bands and ∼700 stars for a near-infrared instrument. For the latter two, many of the targets are nearby M dwarfs. Finally, we identify targets in which Earth-mass planets within the liquid water habitable zone can cause RV amplitudes comparable to the RV photon noise. Assuming the same exposure times as above, we find that an ESPRESSO-like instrument can reach this limit for 1 M⊕ planets in more than 1000 stars. The optical, red optical, and near-infrared configurations reach the limit for 2 M⊕ planets in approximately 500, 700, and 200 stars, respectively. An online tool is provided to estimate the RV photon noise as a function of stellar temperature and brightness and wavelength coverage.

Keywords: radial velocity; high resolution spectroscopy; g dwarf stars; k dwarf stars; m dwarf stars; exoplanets; catalogs
Delivery of Pebbles from the Protoplanetary Disk into Circumplanetary Disks

Small bodies likely existed in the late stage of planet formation either as remnants of the planetesimal formation stage or as fragments of larger planetesimals. Recent studies suggest that they may have played an important role in the formation of regular satellites of giant planets, but their delivery process into the circumplanetary disk has been poorly understood. Using orbital integration that incorporates the gas flow around the planet obtained by hydrodynamic simulation, we examine delivery of small bodies in the protoplanetary disk into circumplanetary disks. We find that large bodies can be captured when they experience strong gas drag near the midplane of the circumplanetary disk, while particles with Stokes number near unity tend to settle toward the midplane of the protoplanetary disk and can be captured near the outer edge of the circumplanetary disk. On the other hand, small particles coupled to the gas can be delivered into the circumplanetary disk with the vertically accreting gas and are captured near the surface of the circumplanetary disk over a wide radial region, if they are sufficiently stirred off the midplane of the protoplanetary disk. However, if the turbulence in the protoplanetary disk is not sufficiently strong, delivery of small particles by such a mechanism would not be efficient. Also, gas depletion in the vicinity of the planet's orbit reduces the efficiency of the delivery. In these cases, larger bodies directly captured by gas drag from the circumplanetary disk would be the major building blocks of regular satellites.

Keywords: protoplanetary disks; exoplanet formation; extrasolar gaseous giant planets; galilean satellites; jovian satellites; natural satellite formation
X-Ray Polarimetry as a Tool to Constrain Orbital Parameters in X-Ray Binaries

X-ray binary systems consist of a companion star and a compact object in close orbit. Thanks to their copious X-ray emission, these objects have been studied in detail using X-ray spectroscopy and timing. The inclination of these systems is a major uncertainty in the determination of the mass of the compact object using optical spectroscopic methods. In this paper, we present a new method to constrain the inclination of X-ray binaries, which is based on the modeling of the polarization of X-rays photons produced by a compact source and scattered off the companion star. We describe our method and explore the potential of this technique in the specific case of the low-mass X-ray binary GS 1826‑238 observed by the Imaging X-ray Polarimetry Explorer observatory.

Keywords: polarimetry; x-ray binary stars; low-mass x-ray binary stars; high mass x-ray binary stars; binary stars; orbit determination; inclination
Updated Catalog of Kepler Planet Candidates: Focus on Accuracy and Orbital Periods

We present a new catalog of Kepler planet candidates that prioritizes accuracy of planetary dispositions and properties over uniformity. This catalog contains 4376 transiting planet candidates, including 1791 residing within 709 multiplanet systems, and provides the best parameters available for a large sample of Kepler planet candidates. We also provide a second set of stellar and planetary properties for transiting candidates that are uniformly derived for use in occurrence rate studies. Estimates of orbital periods have been improved, but as in previous catalogs, our tabulated values for period uncertainties do not fully account for transit timing variations (TTVs). We show that many planets are likely to have TTVs with long periodicities caused by various processes, including orbital precession, and that such TTVs imply that ephemerides of Kepler planets are not as accurate on multidecadal timescales as predicted by the small formal errors (typically 1 part in 106 and rarely >10‑5) in the planets' measured mean orbital periods during the Kepler epoch. Analysis of normalized transit durations implies that eccentricities of planets are anticorrelated with the number of companion transiting planets. Our primary catalog lists all known Kepler planet candidates that orbit and transit only one star; for completeness, we also provide an abbreviated listing of the properties of the two dozen nontransiting planets that have been identified around stars that host transiting planets discovered by Kepler.

Keywords: exoplanet catalogs; exoplanet dynamics; exoplanets; transit photometry; planetary theory
Cascade Model for Planetesimal Formation by Turbulent Clustering

We use a newly developed cascade model of turbulent concentration of particles in protoplanetary nebulae to calculate several properties of interest to the formation of primitive planetesimals and to the meteorite record. The model follows, and corrects, calculations of the primary initial mass function (IMF) of planetesimals by Cuzzi et al., in which an incorrect cascade model was used. Here we use the model of Hartlep et al., which has been validated against several published numerical simulations of particle concentration in turbulence. We find that, for a range of nebula and particle properties, planetesimals may be "born big," formed as sandpiles with diameters in the range 10-100 km, directly from freely floating particles. The IMFs have a modal nature, with a well-defined peak rather than a power-law size dependence. Predictions for the inner and outer parts of the nebula behave similarly in this regard, and observations of primitive bodies in the inner and outer nebula support such modal IMFs. Also, we present predictions of local particle concentrations on several lengthscales in which particles "commonly" find themselves, which have significance for meteoritical observations of the redox state and isotopic fractionation in regions of chondrule formation. An important difference between these results and those of Cuzzi et al. is that particle growth by sticking must proceed to a radius range of at least one to a few centimeters for the IMF and meteoritical properties to be most plausibly satisfied. That is, as far as the inner nebula goes, the predominant "particles" must be aggregates of chondrules (or chondrule-size precursors) rather than individual chondrules themselves.

Keywords: protoplanetary nebulae; planetesimals; planetary system formation; protoplanetary disks; chondrules
A Preferential Growth Channel for Supermassive Black Holes in Elliptical Galaxies at z ≲ 2

The assembly of stellar and supermassive black hole (SMBH) mass in elliptical galaxies since z ~ 1 can help to diagnose the origins of locally observed correlations between SMBH mass and stellar mass. We therefore construct three samples of elliptical galaxies, one at z ~ 0 and two at 0.7 ≲ z ≲ 2.5, and quantify their relative positions in the M BH-M * plane. Using a Bayesian analysis framework, we find evidence for translational offsets in both stellar mass and SMBH mass between the local sample and both higher-redshift samples. The offsets in stellar mass are small, and consistent with measurement bias, but the offsets in SMBH mass are much larger, reaching a factor of 7 between z ~ 1 and z ~ 0. The magnitude of the SMBH offset may also depend on redshift, reaching a factor of ~20 at z ~ 2. The result is robust against variation in the high- and low-redshift samples and changes in the analysis approach. The magnitude and redshift evolution of the offset are challenging to explain in terms of selection and measurement biases. We conclude that either there is a physical mechanism that preferentially grows SMBHs in elliptical galaxies at z ≲ 2, or that selection and measurement biases are both underestimated, and depend on redshift.

Keywords: giant elliptical galaxies; galaxy evolution; supermassive black holes
Jitter Mechanism as a Kind of Coherent Radiation: Constrained by the GRB 221009A Emission at 18 TeV

The emission of gamma-ray burst (GRB) 221009A at 18 TeV has been detected by the large high-altitude air shower observatory. We suggest jitter radiation as a possible explanation for the TeV emission for this energetic GRB. In our scenario, the radiation field is linked to the perturbation field, and the perturbation field is dominated by kinetic turbulence. Kinetic turbulence takes a vital role in both magnetic field generation and particle acceleration. The jitter radiation can reach the TeV energy band when we consider either electron cooling or Landau damping. We further suggest that the jitter radiation in the very high-energy band is coherent emission. Our modeling results can be constrained by the observational results of GRB 221009A in the TeV energy band. This radiation mechanism is expected to have wide applications in the high-energy astrophysical research field.

Keywords: gamma-ray bursts; high energy astrophysics; radiative processes; cosmic magnetic fields theory; magnetic fields; plasma astrophysics
Search for Young and Intermediate-age Stellar Populations in the Galactic Center with Subaru/MOIRCS and CO Narrowband Filters

Extinction toward the Galactic Center (GC) is extreme and limits observations of its stars to the infrared. In addition, the extinction varies on scales of arcseconds. It is therefore highly challenging to distinguish between different stars photometrically and to identify young, massive, or intermediate-age stars that can trace recent star formation. Here we report the results of near-infrared imaging observations of a $6\buildrel{\,\prime}\over{.} 0\times 3\buildrel{\,\prime}\over{.} 3$ region at the GC that encompasses the northwest part of the nuclear star cluster and parts of the nuclear stellar disk. We carried out the observations with the wide-field camera MOIRCS of the Subaru Telescope, using three narrowband (NB) filters. Two of the filters trace the stellar continuum, while we use the third one to measure the strength of the CO absorption features that are prominent in the spectra of cool giants, shallower in the spectra of warmer stars, and absent in young massive stars. Thus, we aim to distinguish between old late-type giants and young and intermediate-age stars. We have found 131 candidates of young and intermediate-age stars. The magnitude limit is ≈11.25 in the extinction-corrected K-band magnitude. The contamination of the candidates by old giants is estimated to be 26%. We show that our method allows us to identify correctly four out of five spectroscopically confirmed massive stars, and 68 of 75 spectroscopically confirmed cool stars (91%). Our results suggest that imaging observations with a CO NB filter can be complementary to other methods to identify massive stars in the GC.

Keywords: galactic center; infrared photometry; narrow band photometry
Quantifying Feedback from Narrow Line Region Outflows in Nearby Active Galaxies. III. Results for the Seyfert 2 Galaxies Markarian 3, Markarian 78, and NGC 1068

Outflows of ionized gas driven by active galactic nuclei (AGN) may significantly impact the evolution of their host galaxies. However, determining the energetics of these outflows is difficult with spatially unresolved observations that are subject to strong global selection effects. We present part of an ongoing study using Hubble Space Telescope and Apache Point Observatory spectroscopy and imaging to derive spatially resolved mass outflow rates and energetics for narrow-line region outflows in nearby AGN that are based on multi-component photoionization models to account for spatial variations in gas ionization, density, abundances, and dust content. This expanded analysis adds Mrk 3, Mrk 78, and NGC 1068, doubling our earlier sample. We find that the outflows contain total ionized gas masses of M ≈ 105.5-107.5 M⊙ and reach peak velocities of v ≈ 800-2000 km s-1. The outflows reach maximum mass outflow rates of ${\dot{M}}_{\mathrm{out}}\approx 3\mbox{--}12\,{M}_{\odot }$ <!-- --> yr-1 and encompass total kinetic energies of E ≈ 1054-1056 erg. The outflows extend to radial distances of r ≈ 0.1-3 kpc from the nucleus, with the gas masses, outflow energetics, and radial extents positively correlated with AGN luminosity. The outflow rates are consistent with in situ ionization and acceleration where gas is radiatively driven at multiple radii. These radial variations indicate that spatially resolved observations are essential for localizing AGN feedback and determining the most accurate outflow parameters. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program Nos. 5140, 5754, 7404, 7573, and 8480. † Based in part on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium.

Keywords: active galaxies; active galactic nuclei; agn host galaxies; emission line galaxies; seyfert galaxies; markarian galaxies; supermassive black holes; galaxy kinematics; galaxy winds; interstellar medium wind
orvara: An Efficient Code to Fit Orbits Using Radial Velocity, Absolute, and/or Relative Astrometry

We present an open-source Python package, Orbits from Radial Velocity, Absolute, and/or Relative Astrometry (orvara), to fit Keplerian orbits to any combination of radial velocity, relative astrometry, and absolute astrometry data from the Hipparcos-Gaia Catalog of Accelerations. By combining these three data types, one can measure precise masses and sometimes orbital parameters even when the observations cover a small fraction of an orbit. The computational performance of orvara is achieved with an eccentric anomaly solver 5-10 times faster than commonly used approaches and low-level memory management to avoid Python overheads and by analytically marginalizing out parallax, barycenter proper motion, and instrument-specific radial velocity zero-points. Through its integration with the Hipparcos and Gaia intermediate astrometry package htof, orvara can properly account for the epoch astrometry measurements of Hipparcos and the measurement times and scan angles of individual Gaia epochs. We configure orvara with modifiable .ini configuration files tailored to any specific stellar or planetary system. We demonstrate orvara with a case study application to a recently discovered white dwarf/main-sequence system, HD 159062. By adding absolute astrometry to literature radial velocity and relative astrometry data, our comprehensive Markov Chain Monte Carlo analysis improves the precision of HD 159062B's mass by more than an order of magnitude to {0.6083}_{-0.0073}^{+0.0083}$ M⊙. We also derive a low eccentricity and large semimajor axis, establishing HD 159062AB as a system that did not experience Roche lobe overflow.

Keywords: orbit determination; keplerian orbit; astronomy software; exoplanet astronomy; astrometric exoplanet detection; radial velocity
Stars That Approach within One Parsec of the Sun: New and More Accurate Encounters Identified in Gaia Data Release 3

Close encounters of stars to the Sun could affect life on Earth through gravitational perturbations of comets in the Oort cloud or exposure to ionizing radiation. By integrating orbits through the Galactic potential, I identify which of 33 million stars in Gaia DR3 with complete phase space information come close to the Sun. 61 stars formally approach within 1 pc, although there is high confidence in only 42 (two thirds) of these, the rest being spurious measurements or (in) binary systems. Most of the stars will encounter within the past or future 6 Myr; earlier/later encounters are less common due to the magnitude limit of the Gaia radial velocities (RVs). Several close encountering stars are identified for the first time, and the encounter times, distances, and velocities of previously known close encounters are determined more precisely on account of the significantly improved precision of Gaia DR3 over earlier releases. The K7 dwarf Gl 710 remains the closest known encounter, with an estimated (median) encounter distance of 0.0636 pc (90% confidence interval 0.0595-0.0678 pc) to take place in 1.3 Myr. The new second closest encounter took place 2.8 Myr ago: this was the G3 dwarf HD 7977, now 76 pc away, which approached within less than 0.05 pc of the Sun with a probability of one third. The apparent close encounter of the white dwarf UPM J0812-3529 is probably spurious due to an incorrect RV in Gaia DR3.

Keywords: space astrometry; solar neighborhood
Exploring Refractory Organics in Extraterrestrial Particles

The origin of organic compounds detected in meteorites and comets, some of which could have served as precursors of life on Earth, remains an open question. The aim of the present study is to make one more step in revealing the nature and composition of organic materials of extraterrestrial particles by comparing infrared spectra of laboratory-made refractory organic residues to spectra of cometary particles returned by the Stardust mission, interplanetary dust particles, and meteorites. Our results reinforce the idea of a pathway for the formation of refractory organics through energetic and thermal processing of molecular ices in the solar nebula. There is also the possibility that some of the organic material had formed already in the parental molecular cloud before it entered the solar nebula. The majority of the IR "organic" bands of the studied extraterrestrial particles can be reproduced in the spectra of the laboratory organic residues. We confirm the detection of water, nitriles, hydrocarbons, and carbonates in extraterrestrial particles and link it to the formation location of the particles in the outer regions of the solar nebula. To clarify the genesis of the species, high-sensitivity observations in combination with laboratory measurements like those presented in this paper are needed. Thus, this study presents one more piece of the puzzle of the origin of water and organic compounds on Earth and motivation for future collaborative laboratory and observational projects.

Keywords: astrochemistry; solar system; laboratory astrophysics; meteorite composition; comet origins