From the ashes of the mysterious core helium flash: Whole Earth Telescope observations of the pulsating subdwarf B star PG0014+067

One of the remaining mysteries of the stars like our Sun is what happens to them after their degenerate helium core ignites. Stars that represent this phase include the so-called subdwarf B (sdB) stars. The recent discovery that some of them pulsate (Kilkenny et al.1997) opens a window to probe their interiors via astreroseismology. One of the most promising pulsating sdB (sdBV) stars for seismic analysis is PG0014+067. Brassard et al. (2001) reported 16 frequencies in the temporal spectrum of this star. As the authors show in their discovery paper this star indeed has very rich spectrum, too rich to be explained only with low order, low degree radial and nonradial p-modes. Therefore, they propose high I modes to explain all the frequencies observed. A more recent suggestion by Kawaler and Hostler (2005) invokes evolutionary models of sdB stars which have rapid internal rotation. With these models, the rich mode density results from the presence of a few triplet (l=1), quintuplet (l-2) and radial (l=0) modes. As a tool to explore the question of possible rotationally split modes by a rapidly rotating cores in sdB stars, PG 0014+067 stands out as an excellent candidate because of the richness of its observed spectrum. To do so we need to determine, unambiguously, the oscillation frequencies present in the star. That is possible only with better frequency resolution and denser longitude coverage. Therefore, we observed this star with the Whole Earth Telescope for two weeks in October 2004. In this thesis I report the results of this multisite campaign. I find that PG0014+067 does not fit any theoretical model currently available