arXiv subjects

P. Dufour

Publications and source records attributed to P. Dufour.

75 records · Page 5Linked to original sources

arXiv2005

Detailed Spectroscopic and Photometric Analysis of DQ White Dwarfs

We present an analysis of spectroscopic and photometric data for cool DQ white dwarfs based on improved model atmosphere calculations. In particular, we revise the atmospheric parameters of the trigonometric parallax sample of Bergeron et al.(2001), and discuss the astrophysical implications on the temperature scale and mean mass, as well as the chemical evolution of these stars. We also analyze 40 new DQ stars discovered in the first data release of the Sloan Digital Sky Survey.

astro-ph↗

arXiv2005

On the Interpretation of High Velocity White Dwarfs as Members of the Galactic Halo

A detailed analysis of 32 of the 38 halo white dwarf candidates identified by Oppenheimer et al. is presented, based on model atmosphere fits to observed energy distributions built from optical BVRI and infrared JHK CCD photometry. Effective temperatures and atmospheric compositions are determined for all objects, as well as masses and cooling ages when trigonometric parallax measurements are available. This sample is combined with that of other halo white dwarf candidates and disk white dwarfs to study the nature of these objects in terms of reduced proper motion diagrams, tangential velocities, and stellar ages. We reaffirm the conclusions of an earlier analysis based on photographic magnitudes of the same sample that total stellar ages must be derived in order to associate a white dwarf with the old halo population, and that this can only be accomplished through precise mass and distance determinations.

astro-ph↗

arXiv2004

Discovery of a Cool, Massive, and Metal-Rich DAZ White Dwarf

We report the discovery of a new metal-rich DAZ white dwarf, GD 362. High signal-to-noise optical spectroscopy reveals the presence of spectral lines from hydrogen as well as CaI, CaII, MgI, and FeI. A detailed model atmosphere analysis of this star yields an effective temperature of Teff = 9740 +/- 50 K, a surface gravity of log g = 9.12 +/- 0.07, and photospheric abundances of log Ca/H = -5.2 +/- 0.1, log Mg/H = -4.8 +/- 0.1, and log Fe/H = -4.5 +/- 0.1. White dwarf cooling models are used to derive a mass of 1.24 Mo for GD 362, making it the most massive and metal-rich DAZ uncovered to date. The problems related to the presence of such large metal abundances in a nearby (d ~ 25 pc) white dwarf in terms of an accretion scenario are briefly discussed.

astro-ph↗