Alina Istrate (University of Wisconsin at Milwaukee)
Résumé
Extremely low-mass white dwarfs (ELM WDs) represent a new class of helium-core white dwarfs characterized by a mass smaller than ~0.25 Msun and with surface gravity in the range 5 < log g < 7. Today we know of the existence of around 100 such objects, with the majority of them found in binary systems with more massive CO WDs. The increasing number of discovered ELM WDs reveals that they can be formed in different environments, from the Galactic disk to open and globular clusters. From an evolutionary point of view, they are most likely the result of binary evolution as they are not expected to form from single stars within a Hubble time. The new wealth of data raises questions regarding puzzling properties of these stars such as, for example, the presence of metals in the atmospheres of young bloated ELM proto-WDs and the recent discovery of pulsations in three ELM proto-WDs. In this talk, I will present our latest theoretical efforts regarding the formation and evolution of ELM WDs.
