Supernova Ia Remnants with M dwarf surviving companions

TL;DR

This study investigates whether an M-dwarf can survive a Type Ia supernova in a single-degenerate progenitor system and whether MV-G272 is such a survivor in the SNR G272.2-3.2. It combines 3D FLASH hydrodynamic simulations of SN ejecta interacting with low-mass M-dwarf companions and subsequent MESA post-impact evolution that includes heating, angular-momentum loss, mass loss, and magnetic braking. The results show final bound masses around 0.44–0.50 M_⊙, kick velocities of order 150–200 km s^{-1}, and substantial early angular-momentum loss; after post-impact evolution with magnetic braking (B ≳ 5 kG) the surface rotation can be slowed to the observed levels, and the HR tracks can reproduce MV-G272’s Teff and luminosity. Overall, the findings support MV-G272 as a plausible surviving companion to the SN Ia in G272.2-3, while highlighting the need for full magnetohydrodynamic modeling to fully capture angular-momentum and surface-contamination signatures.

Abstract

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 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 8.9$σ$ proper motion outlier, although being slowly rotating. Our results show that the properties of this companion (luminosity, effective temperature, surface gravity) can be reproduced by our post-impact M-dwarf models. The slow rotation, which is a common characteristic with 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 G272.2-3.2 SNR.

Figures (10)

• Figure 1: Density profiles of our considered companion models. Different colors represent models with different initial masses.
• Figure 2: Density distribution in the orbital plane at different time snapshots of model M06A20. Each panel is re-centered on the center of the companion star.
• Figure 3: Left: Evolution of the bound mass as a function of time. Right: Evolution of kick velocity (velocity along the direction perpendicular to the orbital velocity) as a function of time. The gray band indicates the observed mass range of the surviving companion candidate MV-G272. Different colors correspond to simulations with companion models of different initial masses. Transparency levels reflect the initial binary separations at the time of the SN explosion, with more transparent lines indicating shorter separations. Line thickness differentiates simulation dimensionality (2D or 3D). Dashed lines represent 3D simulations performed without spin and orbital motions ("noR" models).
• Figure 4: Left: Fractional mass loss (unbound mass relative to initial mass) of the companion as a function of the initial binary separation (normalized by the companion radius). Right: Kick velocity perpendicular to the orbital motion as a function of the normalized binary separation. Different colors represent companion models with different initial masses. Markers differentiate simulation dimensionalities: 2D (circles), 3D-noR (triangles), and 3D (squares).
• Figure 5: The evolution of the spin angular momentum magnitude as a function of time is shown. Different colors represent the angular momentum magnitudes from various 3D models with pre-explosion spin and rotation. The spin angular momentum is computed in the center-of-mass frame of the surviving companion, considering only the bound gas.