EVIDENCE FOR TEMPERATURE CHANGE AND OBLIQUE PULSATION FROM LIGHT CURVE FITS OF THE PULSATING WHITE DWARF GD 358
- Department of Astronomy and McDonald Observatory, University of Texas at Austin, Austin, TX (United States)
- Delaware Asteroseismic Research Center, Mt. Cuba Observatory, Greenville, DE (United States)
- Departamento de Fisica Universidade Federal de Santa Catarina, C.P. 476, 88040-900, Florianopolis, SC (Brazil)
- Department of Astronomy, University of Washington, Seattle, WA (United States)
- Department of Physics and Astronomy, University of Delaware, Newark, DE (United States)
- Instituto de FIisica UFRGS, C.P. 10501, 91501-970 Porto Alegre, RS (Brazil)
- Institut fuer Theoretische Physik und Astrophysik, Universitaet Kiel, 24098 Kiel (Germany)
Convective driving, the mechanism originally proposed by Brickhill for pulsating white dwarf stars, has gained general acceptance as the generic linear instability mechanism in DAV and DBV white dwarfs. This physical mechanism naturally leads to a nonlinear formulation, reproducing the observed light curves of many pulsating white dwarfs. This numerical model can also provide information on the average depth of a star's convection zone and the inclination angle of its pulsation axis. In this paper, we give two sets of results of nonlinear light curve fits to data on the DBV GD 358. Our first fit is based on data gathered in 2006 by the Whole Earth Telescope; this data set was multiperiodic containing at least 12 individual modes. Our second fit utilizes data obtained in 1996, when GD 358 underwent a dramatic change in excited frequencies accompanied by a rapid increase in fractional amplitude; during this event it was essentially monoperiodic. We argue that GD 358's convection zone was much thinner in 1996 than in 2006, and we interpret this as a result of a short-lived increase in its surface temperature. In addition, we find strong evidence of oblique pulsation using two sets of evenly split triplets in the 2006 data. This marks the first time that oblique pulsation has been identified in a variable white dwarf star.
- OSTI ID:
- 21450889
- Journal Information:
- Astrophysical Journal, Vol. 716, Issue 1; Other Information: DOI: 10.1088/0004-637X/716/1/84; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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