Projeto Observacional para 2007B - SO2007B-018

Autor: Kepler de Souza Oliveira
Instituição: UFRGS
e-mail: kepler@if.ufrgs.br

Co-autores:
Barbara Garcia Castanheira

Título: Diamond Bells

Resumo: Massive white dwarfs are of great interest in studying the extremes of stellar evolution and, potentially, in understanding the progenitors of Type Ia SNe. Using mainly SNR~20 spectra acquired by SDSS, we have identified 4 DA white dwarf stars brighter than g=19 with mass determinations above 1.0 MSun, with Teff within the instability strip of the ZZ Ceti stars. To date 141 ZZ Ceti stars have been discovered, 107 of them by us and our collaborators, mainly using the effective temperatures derived from SDSS spectra. There is around 90% chance of finding a new variable within the range 12300K < Teff < 10850K. As seismology is the only way to study the structure of stars, we propose to look for pulsations in these 4 massive stars. The only massive ZZ Ceti known to date, BPM3093, was discovered by our group at LNA. With seismology we proved it is partially crystallized, proving a 40 yr old prediction that Coulomb interactions crystallize a star with mass above 1.0 Msun and Teff < 12000K. As the 4 new candidates are even more massive than BPM37093, and have Teff inside the ZZ Ceti instability strip, they should pulsate and, with time, we should be able to apply seismology to derive their internal structure, essential for understanding the progenitors of SNIa, through accretion onto massive white dwarfs.