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Paper: HST Observations of the Pulsating White Dwarf GD 358
Volume: 334, 14th European Workshop on White Dwarfs
Page: 549
Authors: Castanheira, B.G.; Kepler, S.O.; Nitta, A.; Winget, D.E.; Koester, D.
Abstract: We used time-resolved ultraviolet spectroscopy obtained with the FOS and STIS spectrographs of the Hubble Space Telescope (HST), together with archival IUE observations to measure the effective temperature (Teff), surface gravity (log g) and distance (d) of the pulsating DB white dwarf GD 358 with unprecedented accuracy, and to show the temperature did not change during the 1996 sforzando, when the star changed basically to a single mode pulsator. We also measured, for the first time for a DBV, the spherical harmonic degree (l) for two modes, with k = 8 and k = 9, which was only possible because the stellar light curve was dominated by a single mode in 1996. In addition, we constrain l to be 1 or 2 for the main pulsations in the normal multiperiodic state. The spectra are best fit for Teff = 24,100 ± 400 K, log g = 7.91 ± 0.26 and d = 42.7 ± 2.5 pc. The ultraviolet spectroscopic distance is in better agreement with the seismological value, than the one derived by parallax.
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