Search Publications
A Comprehensive Spectroscopic Analysis of DB White Dwarfs
Fontaine, G.; Bergeron, P.; Wesemael, F. +9 more
We present a detailed analysis of 108 helium-line (DB) white dwarfs based on model atmosphere fits to high signal-to-noise optical spectroscopy. We derive a mean mass of 0.67 M sun for our sample, with a dispersion of only 0.09 M sun. White dwarfs also showing hydrogen lines, the DBA stars, comprise 44% of our sample, and the…
The Be Star Spectra (BeSS) Database
Neiner, C.; Floquet, M.; de Batz, B. +3 more
Be stars vary on many timescales, from hours to decades. A long time base of observations to analyze certain phenomena in these stars is therefore necessary. Collecting all existing and future Be star spectra into one database has thus emerged as an important tool for the Be star community. Moreover, for statistical studies, it is useful to have c…
An Ultraviolet Spectroscopic Atlas of Local Starbursts and Star-forming Galaxies: The Legacy of FOS and GHRS
Heckman, Timothy M.; Calzetti, Daniela; Leitherer, Claus +1 more
We present 46 rest-frame ultraviolet (UV) spectra of 28 local starburst and star-forming galaxies which were observed with the Faint Object Spectrograph (FOS) and the Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) at a spectral resolution of a few 100 km s-1. We compare the HST spectra with lower resolut…
Rocky Extrasolar Planetary Compositions Derived from Externally Polluted White Dwarfs
Koester, D.; Zuckerman, B.; Klein, B. +1 more
We report Keck High Resolution Echelle Spectrometer data and model atmosphere analysis of two helium-dominated white dwarfs, PG1225-079 and HS2253+8023, whose heavy pollutions most likely derive from the accretion of terrestrial-type planet(esimal)s. For each system, the minimum accreted mass is ~1022 g, that of a large asteroid. In PG1…
Emission Lines from the Gas Disk around TW Hydra and the Origin of the Inner Hole
Pascucci, I.; Najita, J.; Hollenbach, D. +1 more
We compare line emission calculated from theoretical disk models with optical to submillimeter wavelength observational data of the gas disk surrounding TW Hya and infer the spatial distribution of mass in the gas disk. The model disk that best matches observations has a gas mass ranging from ~10-4 to 10-5 M sun fo…
Early magnetic B-type stars: X-ray emission and wind properties
Hamann, W. -R.; Oskinova, L. M.; Ignace, R. +3 more
We present a comprehensive study of X-ray emission by, and wind properties of, massive magnetic early B-type stars. Dedicated XMM-Newton observations were obtained for three early-type B-type stars, ξ1 CMa, V2052 Oph and ζ Cas, with recently discovered magnetic fields. We report the first detection of X-ray emission from V2052 Oph and ζ…
The mesosphere and lower thermosphere of Titan revealed by Cassini/UVIS stellar occultations
Sandel, B. R.; West, R. A.; Yelle, R. V. +5 more
Stellar occultations observed by the Cassini/UVIS instrument provide unique data that probe the mesosphere and lower thermosphere of Titan at altitudes between 400 and 1400 km. This region is a site of complex photochemistry that forms hydrocarbon and nitrile species, and plays a crucial role in the formation of the organic hazes observed in the s…
An asteroseismic study of the O9V star HD 46202 from CoRoT space-based photometry
Auvergne, M.; Baudin, F.; Michel, E. +13 more
The O9V star HD 46202, which is a member of the young open cluster NGC 2244, was observed by the CoRoT satellite in October/November 2008 during a short run of 34 days. From the very high-precision light curve, we clearly detect β Cep-like pulsation frequencies with amplitudes of ~0.1 mmag and below. A comparison with stellar models was performed …
Constraining the structure of the planet-forming region in the disk of the Herbig Be star HD 100546
Pinte, C.; Ménard, F.; Weigelt, G. +8 more
Context. Studying the physical conditions in circumstellar disks is a crucial step toward understanding planet formation and disk evolution. Of particular interest is the case of HD 100546, a Herbig Be star that presents a gap within the first 13 AU of its protoplanetary disk, a gap that may originate in the dynamical interactions of a forming pla…
Supermassive Black Hole Mass Estimates Using Sloan Digital Sky Survey Quasar Spectra at 0.7 < z < 2
Hall, Patrick B.; Rafiee, Alireza
We present Mg II-based black hole (BH) mass estimates for 27,602 quasars with rest-frame UV spectra available in the Sloan Digital Sky Survey Data Release Three. This estimation is possible due to the existence of an empirical correlation between the radius of the broad-line region (BLR) and the continuum luminosity at 3000 Å. We regenerate this c…