I use recent observations of circumstellar matter (CSM) around type Ia supernovae (SNe Ia) to estimate the fraction of SNe Ia that explode into a planetary nebula (PN) and to suggest a new delay time distribution from the common envelope evolution (CEE) to the SN Ia explosion for SNe Ia that occur shortly after the CEE. Under the assumption that the CSM results from a CEE, I crudely estimate that about 50% of all SNe Ia are SNe Ia inside PNe (SNIPs), and that the explosions of most SNIPs occur within a CEE to explosion delay (CEED) time of less than about ten thousand years. I also estimate that the explosion rate of SNIPs, i.e., the CEED time distribution, is roughly constant within this timescale of ten thousand years. The short CEED time suggests that a fraction of SNIPs come from the core-degenerate (CD) scenario where the merger of the core with the white dwarf takes place at the end of the CEE. I present my view that the majority of SNIPs come from the CD scenario. I list some further observations that might support or reject my claims, and describe the challenge to theoretical studies to find a process to explain a merger to explosion delay (MED) time of up to ten thousand years or so. A long MED will apply also to the double degenerate scenario.
- (stars:) binaries (including multiple): close
- (stars:) supernovae: general
- (stars:) white dwarfs
- ISM: supernova remnants