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Projeto Observacional para 2003A - I17

Autor: Alex Fabiano Murillo da Costa
Instituição: IF/UFRGS 
e-mail: murillo@if.ufrgs.br

Co-autores:
Kepler de Souza Oliveira Filho
Odilon Giovannini
José Eduardo S. Costa
Barbara Garcia Castanheira
Marcio Gabriel dos Santos
Virginia Mello Alves

Título: Asteroseismology of the pulsating sdB star and Suspected  SNe Ia Progenitor KPD 1930+2752: A Whole Earth Telescope Campaing.

Resumo: We propose to observe KPD 1930+2752, a pulsating subdwarf B star with a particularly rich period spectrum that is also a short period (~2h17m) close binary system (as revealed by the presence of an ellipsoidal variation in the lightcurve). The companion is almost certainly a white dwarf as there are no indications of eclipse or re e ect. Radial velocity measurements indicate that the total mass of the system exceeds the Chan- drasekhar limit, making KPD 1930+2752 the first known (non-X-ray source) candidate for a Type Ia supernova progenitor. The pair should merge within an astrophysically interesting timescale (~200 Myr) due to gravitational wave radiation. Additionally, the tidal distortions are indicative of the strong tidal force incurred on the pulsating star by its companion. This will allow us to investigate the effects such strong tidal forces have on pulsations. Due to its outstanding astrophysical interest, this object is the primary target of the WET network Xcov 23 campaign. The goal is to fully resolve the complex pulsation pattern of the pulsating sdB star, as well as the details of the ellipsoidal modulation. The asteroseismological analysis of the pulsation data, along with a detailed analysis of the folded, high S/N ratio ellipsoidal variation will lead to strong physical constraints on this particularly interesting and, so far, unique stellar object.