A Double-degenerate Scenario with a Merger to Explosion Delay Time to Explain Type Ia Supernova SN 2020aeuh

Abstract I suggest the double-degenerate (DD) scenario with a merger-to-explosion delay (MED) time (the DD-MED scenario) of about 1–2 yr to explain the rare properties of the recently analyzed type Ia supernova (SN Ia) SN 2020aeuh. The rare properties are the SN Ia ejecta interacting with a carbon–oxygen (CO)-rich circumstellar material (CSM) at approximately 50 days post-explosion. In this DD-MED scenario, two massive CO white dwarfs (WDs), with masses of M 1 ≃ 1.1 M ⊙ and M 2 ≃ 1 M ⊙ , merge to leave a rapidly rotating lonely WD of about the Chandrasekhar mass. The merger process ejects M CSM ≃ 0.7 M ⊙ to form a nonspherical CO-rich CSM. At the explosion, there is a lonely WD and a detached hydrogen- and helium-deficient CSM. Studies proposed the other lonely WD scenario, the core-degenerate (CD) scenario, to explain several specific SNe Ia and SN Ia remnants. SN 2020aeuh is the first particular SN Ia that is attributed to the DD-MED scenario. Besides being slightly brighter than typical SNe Ia and the CSM interaction, SN 2020aeuh is a normal SN Ia. Therefore, this study strengthens the claim of earlier studies, which are based on other arguments, like the properties of SN Ia remnants, that the lonely WD scenarios, i.e., the DD-MED and CD scenarios, might account for most, if not all, normal SNe Ia. These earlier studies also argue that all SN Ia scenarios, whether lonely WD or not, might contribute to peculiar SNe Ia.