Evolution of Carbon-Oxygen White Dwarf Accreting Helium as One of the Progenitors of Accretion-induced Collapse

Abstract

Carbon-oxygen white dwarf (CO WD) and helium star binary is one of the ways that can lead to accretion-induced collapse (AIC). The continuous accretion may increase the mass of the white dwarf until at a certain condition, carbon burning off-center might be initiated and alter CO into ONe WD. This paper is intended to analyze the long-term evolution of the CO WD accreting helium material. The stellar evolution code used in this research is MESA (Modules for Experiments in Stellar Astrophysics). MESA creates CO WD by evolving ZAMS star with an initial mass of 6 M⊙ to produce 0.9 M⊙ CO WD. The accretion rates are 4×10−6 and 4×10−7 M⊙/year which consist of mostly helium. It shows that for the high accretion rate, the helium burning on the surface of the WD is stable. It is predicted that it will continue to be stable for a very long time because of the high supply of matter. For the lower one, the burning experiences a fluctuation from the beginning of the accretion. For both cases, if carbon burning off-center has occurred, it may lead to the creation of ONe WD and eventually AIC.