NEW INSIGHTS INTO THE PROBLEM OF THE SURFACE GRAVITY DISTRIBUTION OF COOL DA WHITE DWARFS
- Departement de Physique, Universite de Montreal, C.P. 6128, Succursale Centre-Ville, Montreal, QC H3C 3J7 (Canada)
We review at length the longstanding problem in the spectroscopic analysis of cool hydrogen-line (DA) white dwarfs (T{sub eff}< 13,000 K) where gravities are significantly higher than those found in hotter DA stars. The first solution that has been proposed for this problem is a mild and systematic helium contamination from convective mixing that would mimic the high gravities. We constrain this scenario by determining the helium abundances in six cool DA white dwarfs using high-resolution spectra from the Keck I 10 m telescope. We obtain no detections, with upper limits as low as He/H = 0.04 in some cases. This allows us to put this scenario to rest for good. We also extend our model grid to lower temperatures using improved Stark profiles with non-ideal gas effects from Tremblay and Bergeron and find that the gravity distribution of cool objects remains suspiciously high. Finally, we find that photometric masses are, on average, in agreement with expected values, and that the high-log g problem is so far unique to the spectroscopic approach.
- OSTI ID:
- 21394186
- Journal Information:
- Astrophysical Journal, Vol. 712, Issue 2; Other Information: DOI: 10.1088/0004-637X/712/2/1345; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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