Seismology Of White Dwarfs: The ZZ Ceti Stars

We calculate an extensive adiabatic model grid for pulsating white dwarfs with H dominated atmospheres, the ZZ Ceti stars. We developed a new approach for asteroseismology, using the relative observed amplitudes as weights, and compared the computed modes with the observed ones for the class of ZZ Ceti stars. We measure the H layer mass for 83 stars and found an average of M(H)/M() = 10(-6.3), which is thinner than the predicted value of M(H)/M() = 10(-4). Our results indicate that the stars lose more mass during their evolution than previously expected.