Type Ia Single Degenerate Survivors Must Be Overluminous

TL;DR

The paper demonstrates that surviving donor stars in the single-degenerate Type Ia supernova scenario should be overluminous for thousands of years post-explosion, and the absence of such stars in observations challenges this model.

Contribution

It provides a detailed evolutionary model predicting overluminosity of donor stars after supernova explosions, offering observational tests that challenge the single-degenerate scenario for Type Ia supernovae.

Findings

Survivor stars must be significantly more luminous for 1,000 to 10,000 years post-explosion.

Lack of observed luminous survivors in certain supernova remnants challenges the SD scenario.

Nearby supernovae have been ruled out as SD progenitors based on these luminosity constraints.

Abstract

In the single-degenerate (SD) channel of a Type Ia supernovae (SN Ia) explosion, a main-sequence (MS) donor star survives the explosion but it is stripped of mass and shock heated. An essentially unavoidable consequence of mass loss during the explosion is that the companion must have an overextended envelope after the explosion. While this has been noted previously, it has not been strongly emphasized as an inevitable consequence. We calculate the future evolution of the companion by injecting 2-6 10^47 ergs into the stellar evolution model of a 1 Msun donor star based on the post-explosion progenitors seen in simulations. We find that, due to the Kelvin-Helmholtz collapse of the envelope, the companion must become significantly more luminous (10 - 10^3 Lsun) for a long period of time (10^3 - 10^4 years). The lack of such a luminous "leftover" star in the LMC supernova remnant SNR 0609-67.5 provides another piece of evidence against the SD scenario. We also show that none of the stars proposed as the survivors of the Tycho supernova, including Tycho G, could plausibly be the donor star. Additionally, luminous donors closer than ~10 Mpc should be observable with the Hubble Space Telescope starting ~2 years post-peak. Such systems include SN 1937C, SN 1972E, SN 1986G, and SN 2011fe. Thus, the SD channel is already ruled out for at least two nearby SNe Ia and can be easily tested for a number of additional ones. We also discuss similar implications for the companions of core-collapse SNe.