Evolution and Asteroseismology of Pulsating Low-Mass White Dwarfs

L. M. CALCAFERRO; A. D. ROMERO; A. H. CÓRSICO; S. O. KEPLER; L. G. ALTHAUS

Austin, Texas

Workshop; 21st European White Dwarf Workshop held July 23-27, 2018, Austin, Texas; 2018

Many low-mass white dwarfs are being discovered in the field of ourgalaxy and some of them exhibit $g$-mode pulsations, comprising theextremely low-mass variable (ELMV) stars class. Despite it is generallybelieved that these stars are characterized by thick H envelopes, fromstellar evolution considerations, the existence of low-mass WDs withthin H envelopes is also possible. We have performed detailedasteroseismological fits to all the known ELMVs to search for arepresentative model by employing a set of fully evolutionary modelsthat are representative of low-mass He-core white dwarf stars with arange of stellar masses $[0.1554-0.4352] M_{odot}$, effectivetemperatures $[6000-10000] $K, and also with a range of H envelopethicknesses $-5.8 lesssim log(M_{m H}/M_{star}) lesssim -1.7$,hence expanding the space of parameters. We found that some of the starsunder analysis are characterized by thick H envelopes, but others arebetter represented by models with thin H envelope.