Destratification in the Progenitor Interior of the Mg-rich Supernova Remnant N49B

TL;DR

This paper proposes that the elemental composition of supernova remnant ejecta, specifically Mg-rich material, can reveal intense shell burning and destratification in progenitor stars' final stages, providing a new observational diagnostic.

Contribution

It introduces a novel method using X-ray observations of O-rich ejecta to detect shell merging activity in massive star progenitors before supernova explosions.

Findings

Mg-rich ejecta in N49B indicates shell merging activity.

High Mg/Ne ratio suggests destruction of stratification in progenitor.

Supports shell destratification as a common process in some massive stars.

Abstract

Simulations of pre-supernova evolution suggest that some intense shell burning can be so active that, in extreme cases, it can merge with the outer shell, changing the initial conditions for the supernova explosion. However, such violent activity in the interior of stars has been difficult to confirm from observations of stars. Here we propose that the elemental composition of O-rich ejecta in supernova remnants can be a tool to test for this kind of intense shell burning activity in the final stages of progenitor evolution. As an example, we discuss the origin of "Mg-rich" ejecta in the supernova remnant N49B. A high Mg/Ne mass ratio $\gtrsim 1$ suggests that the Ne- or O-burning shell has broken into or merged with the outer shell before the collapse. Such Mg-rich (or Ne-poor) ejecta has been identified in some other supernova remnants, supporting the idea that some destratification process, such as a shell merger, does indeed occur in the interiors of some massive stars, although they may not be the majority. Our results suggest that X-ray observations of O-rich ejecta in core-collapse supernova remnants will be a unique tool to probe the shell burning activity during the final stage of a massive star's interior.