HST Observation of GD 358
Kepler, S. O.; Winget, D. E.; Koester, D.; Nitta, A.; Jiang, Xiaojun; Zola, S.; Krzesinski, J.; Pajdosz, G.
United States, Brazil, Germany, Poland, China
Abstract
The success of asteroseismology lies in the correct identification of the star's normal modes of oscillation. Winget et al. (1994) identified the normal modes of a helium white dwarf pulsator, GD 358, through the frequency distribution of the pulsation. Robinson et al. (1995) described a new mode identification method by comparing the pulsation amplitudes in the ultraviolet and optical ranges. In order to cross-calibrate the two mode identification methods, we decided to apply the method used by Robinson et al. to GD 358. In August 1996, the Hubble Space Telescope took time-series spectroscopic data of GD 358 using the Faint Object Spectrograph. We also obtained nearly simultaneous ground-based optical data necessary to apply the method of Robinson et al. At this stage, we can only rule out the possibility of l=3 for the three modes we analyzed, but cannot determine to which l value the modes correspond.