2026ApJ...996...35P

We study the possibility that Type Ia supernovae might be produced by binary systems where the companion of the exploding white dwarf is an M-dwarf star. Such a companion would appear as a runaway star, retaining its pre-explosion orbital velocity along with a kick imparted by the supernova ejecta. It might be rapidly rotating, from being tidally locked with the white dwarf prior to explosion in a very close binary. For this study, we perform a series of multidimensional hydrodynamic simulations to investigate the interaction between M-dwarf companions and SN ejecta, followed by post-impact stellar evolution modeling using the MESA code. Our initial models in the 3D simulations had high spin angular momenta, and the effects of magnetic braking have been included. They very significantly reduce the final rotation. A surviving companion candidate, MV-G272, has recently been discovered in the supernova remnant G272.2-3.2, which is an 8.9σ proper motion outlier, although it is slowly rotating. Our results show that the properties of this companion (luminosity, effective temperature, and surface gravity) can be reproduced by our post-impact M-dwarf models. The slow rotation, which is a common characteristic of several proposed hypervelocity SN companions, can be explained by magnetic braking during the post-impact evolution, thus supporting the possibility that the MV-G272 star is the surviving companion of the Type Ia supernova now found as supernova remnant G272.2-3.2.