Supernova remnant 0509-67.5 is consistent with an explosion inside an old planetary nebula (SNIP)

Abstract

I critically examine claims in the paper arXiv:2608.11978 that the double-detonation (DDet) scenario explains the type Ia supernova (SN Ia) remnant (SNR Ia) SNR 0509-67.5, and find the arguments supporting the DDet scenario weak; hence, I reiterate my claim that the core-degenerate (CD) scenario, where a lonely white dwarf (WD), which is the merger product of a lower-mass WD and the core of an asymptotic giant branch star, exploded inside an old planetary nebula, i.e., an SNIP, best explains SNR 0509-67.5. I find that the flat edge of the SNR in the north-northeast, which in the DDet scenario is due to a shadow by the companion to the WD that exploded, is not unique in this SNR, and that the circumstellar matter, i.e., an old planetary nebula, shaped this edge, as well as other structures on the edge of this SNR. I emphasize that analyses of SNRs Ia and SNe Ia at late stages must consider the claim that most normal SNe Ia are SNIPs, implying that old planetary nebulae can heavily shape their morphologies. The bulk velocity inferred from an iron emission line in SNR 0509-67.5, which the DDet explosion attributes to the orbital motion of the exploding WD around its companion, can be an outcome of the explosion of a near-Chandrasekhar lonely WD; an off-center delayed-detonation transition explosion can form asymmetrical nucleosynthesis, while leading to a bulk motion of nickel that decays to iron. I repeat my claim that the CD scenario of a SNIP is the most likely scenario for SNR 0509-67.5.