2025/12/03 by Meng, Xiang-Cun, Podsiadlowski, Philipp
#FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE) #Solar and Stellar Astrophysics (astro-ph.SR)
paper · doi:10.48550/arxiv.2512.03531
SN 2020eyj is the first type Ia supernova (SN Ia) showing the signature of a compact helium-rich circumstellar material (CSM). Such a large CSM is difficult to explain in a single-degenerate scenario where the donor star is a helium star. Here we show that, under certain conditions, it is possible that the transfer of helium leads to a common envelope (CE) engulfing the system, similar to the common-envelope wind model proposed by Meng & Podsiadlowski (2017). If in such a helium common-envelope wind (HeCEW) model the initial white dwarf (WD) mass is larger than 1.1 M\rm \odot and the helium star more massive than 1.8 M\rm \odot, the mass of a helium CE can be larger than 0.3 M\rm \odot prior to supernova explosion. The CE mass heavily depends on the initial parameters of the binary system. A dynamical CE ejection event could occur shortly before the supernova, and then our model may naturally explain the properties of SN 2020eyj, specifically the massive He-rich CSM, its dim peak brightness, low ejecta velocity and low birth rate.