Evolution and Asteroseismology of Pulsating Low-Mass White Dwarfs

Many low-mass white dwarfs are being discovered in the field of our galaxy and some of them exhibit g-mode pulsations, comprising the extremely low-mass variable (ELMV) stars class. Although it is generally believed that these stars are characterized by thick H envelopes, the existence of low-mass WDs with thin H envelopes is also possible from stellar evolution considerations. We have performed detailed asteroseismological fits to all the known ELMVs to search for a representative model by employing a set of fully evolutionary models that are representative of low-mass He-core white dwarf stars with a range of stellar masses [0.1554-0.4352]M , effective temperatures [6000 - 10000] K, and also with a range of H envelope thicknesses -5:8 ~< log(MH/M*) ~< -1.7, hence expanding the space of parameters. We found that some of the stars under analysis are characterized by thick H envelopes, but others are better represented by models with a thin H envelope.