FM17p.30 — Pulsating Helium Atmosphere White Dwarfs

Date & Time

Aug 10th at 6:00 PM until 6:00 PM

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Author(s): Judith Provencal4, Michael H. Montgomery5, Agnes Bischoff-Kim3, Harry Shipman4, Atsuko Nitta1, Whole Earth Telescope Collaboration2

Institution(s): 1. Gemini North, 2. Mt. Cuba Observatory, 3. Penn State Worthington, 4. University of Delaware, 5. University of Texas

The overwhelming majority of all stars currently on the main sequence as well as those from earlier generations will or have ended their stellar lives as white dwarf stars. White dwarfs are rich forensic laboratories linking the history and future evolution of our Galaxy. Their structure and atmospheric composition provide evidence of how the progenitors lived, how they evolved, and how they died. This information reveals details of processes governing the behavior of contemporary main sequence stars. Combined with their distribution in luminosity/temperature, white dwarfs strongly constrain models of galactic and cosmological evolution.
GD358 is among the brightest (mv =13.7) and best studied of the pulsating white dwarfs. This helium atmoshere pulsator (DBV) has an extensive photometric database spanning 30 years, including nine multisite Whole Earth Telescope campaigns. GD358 exhibits a range of behaviors, from drastic changes in excited pulsation modes to variable multiplet splittings. We use GD358 as a template for an examination of the DBV class, combining photometric results with recent COS spectroscopy. The results present new questions concerning DB formation and evolution.