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Paper: Time-Series Spectroscopy of DAVs
Volume: 334, 14th European Workshop on White Dwarfs
Page: 471
Authors: Thompson, S.E.; Clemens, J.C.; Koester, D.
Abstract: Optical time-series spectroscopy of pulsating white dwarf stars has the potential to identify the spherical degrees of individual pulsation modes. We introduce a new analysis technique that improves our ability to measure the line shape variations and consequently the identity of the modes. We show the analysis of time-series spectra of three stars: PY Vul, G 226-29, and EC 23487- 2424. Most notably, the results of our analysis of PY Vul provides a solution to all the peculiar aspects of the pulsations that have set this star apart from the other DAVs. These aspects include low pulsation amplitudes, a harmonic mode that exceeds the amplitude of its fundamental, and a mode with unexplained UV amplitudes. The addition of our optical time-series spectra reveals that the mode with unusual UV amplitudes has line profile variations consistent with a spherical degree of four. We discuss how all the observations of this star are accounted for by PY Vul being dominated by an l = 4 mode, and propose this hypothesis as a solution to the mysteries of PY Vul.
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