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ON THE PURITY OF THE ZZ CETI INSTABILITY STRIP: DISCOVERY OF MORE PULSATING DA WHITE DWARFS ON THE BASIS OF OPTICAL SPECTROSCOPY
We report the discovery of two new ZZ Ceti pulsators, LP 133-144 and HE 1258+0123, selected on the basis of model atmosphere fits to optical spectroscopic data. The atmospheric parameters for LPExpand
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An independent method for determining the age of the universe
An age of 9.3 + or - 2.0 Gyr is derived for the Galactic disk on the basis of comparisons between the sudden drop in the observed luminosity distribution and theoretical evolutionary white dwarfExpand
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The Pulsating White Dwarf Stars
We present a summary of what is currently known about the three distinct families of isolated pulsating white dwarfs. These are the GW Vir stars (He/C/O-atmosphere stars with Teff 120,000 K), theExpand
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COOLING SEQUENCES AND COLOR-MAGNITUDE DIAGRAMS FOR COOL WHITE DWARFS WITH HYDROGEN ATMOSPHERES
We present new cooling sequences, color-magnitude diagrams, and color-color diagrams for cool white dwarfs with pure hydrogen atmospheres down to an effective temperature Teff = 1500 K. We include aExpand
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Detailed compositional analysis of the heavily polluted DBZ white dwarf SDSS J073842.56+183509.06: A window on planet formation?
We present a new model atmosphere analysis of the most metal-contaminated white dwarf known, the DBZ SDSS J073842.56+183509.06. Using new high-resolution spectroscopic observations taken with KeckExpand
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Adiabatic Survey of Subdwarf B Star Oscillations. III. Effects of Extreme Horizontal Branch Stellar Evolution on Pulsation Modes
We present the final results of a large, systematic survey of the adiabatic oscillation properties of models of subdwarf B (sdB) stars. This survey is aimed at providing the minimal theoreticalExpand
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A Driving Mechanism for the Newly Discovered Long-Period Pulsating Subdwarf B Stars
We present the results of a stability survey carried out for a sequence of representative models of subdwarf B stars spanning the range of effective temperature 22; 000 KTeff � 38; 000 K. We showExpand
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THE DISCOVERY OF THE MOST METAL-RICH WHITE DWARF: COMPOSITION OF A TIDALLY DISRUPTED EXTRASOLAR DWARF PLANET
Cool white dwarf stars are usually found to have an outer atmosphere that is practically pure in hydrogen or helium. However, a small fraction have traces of heavy elements that must originate fromExpand
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Understanding the Cool DA White Dwarf, G29-38
The white dwarfs are promising laboratories for the study of cosmochronology and stellar evolution. Through observations of the pulsating white dwarfs, we can measure their internal structures andExpand
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