The formation of DA white dwarfs with thin hydrogen envelopes

We study the formation and evolution of DA white dwarfs, the progenitors of which have experienced a late thermal pulse (LTP) shortly after the departure from the thermally pulsing AGB. To this end, we compute the complete evolution of an initially $2.7~M_{\odot}$star all the way from the zero-age main sequence to the white dwarf stage. We find that most of the original H-rich material of the post-AGB  remnant is burnt during the post-LTP evolution, with the result that, at entering its white dwarf cooling track, the remaining H envelope becomes $10^{-6}~M_{\odot}$in agreement with asteroseismological inferences for some ZZ Ceti stars.