The Origin of the Mg-rich Supernova Remnant J0550-6823 and the Frequency of Similar Events in the Large Magellanic Cloud

TL;DR

This paper investigates the origin of the Mg-rich supernova remnant J0550-6823 in the Large Magellanic Cloud, linking its properties to stellar interior processes and estimating the frequency of similar events to inform stellar evolution models.

Contribution

It reanalyzes X-ray data of J0550-6823, confirming its Mg-rich nature, and estimates that 10-40% of massive stars in the LMC have extended convective shells affecting supernova outcomes.

Findings

J0550-6823 is confirmed as Mg-rich with a low Ne/Mg ratio.

Approximately 2-3 Mg-rich SNRs are in the LMC.

An estimated 10-40% of massive stars in the LMC have extended convective shells.

Abstract

Shell burning and internal mixing in massive stars play an important role in setting the initial conditions for core-collapse supernova explosions. In the late stages of stellar evolution, intense shell burning can cause distinct convective regions to merge, fundamentally restructuring the stellar interior. Although such phenomena are difficult to observe directly, the observation of ``Mg-rich'' supernova remnants (SNRs) has recently emerged as a potential signature of these events. In this study, we reanalyze X-ray observations of J0550--6823, a SNR in the Large Magellanic Cloud (LMC) and a new candidate Mg-rich SNR. Our spectral analysis confirms a low Ne/Mg mass ratio of $\approx$1, and its classification as Mg-rich. By comparing the observational results with pre-supernova models, we suggest that the progenitor of J0550-6823 likely had an extended convective shell that reduces the Ne/Mg ratio prior to its explosion. Furthermore, we observe that $\sim$2--3 Mg-rich SNRs exist in the LMC, suggesting that $\lesssim$10--40\% of massive stars in the LMC may have had an extended convective shell, similar to what we observed in J0550-6823. This fraction would be important for understanding the final stages of the evolution of massive stars and galactic chemical evolution.