N49: the first robust discovery of a recombining plasma in an extra galactic supernova remnant

TL;DR

This paper reports the first robust detection of a recombining plasma in an extragalactic supernova remnant, N49 in the Large Magellanic Cloud, highlighting its potential link to core-collapse origins and mixed-morphology characteristics.

Contribution

It provides the first definitive evidence of a recombining plasma in an extragalactic SNR, expanding understanding of plasma states beyond the Milky Way.

Findings

N49 is in a recombining plasma state.

Recombining plasmas are associated with mixed-morphology SNRs.

No clear recombining plasma evidence in N23.

Abstract

Recent discoveries of recombining plasmas (RPs) in supernova remnants (SNRs) have dramatically changed our understanding of SNR evolution. To date, a dozen of RP SNRs have been identified in the Galaxy. Here we present Suzaku deep observations of four SNRs in the Large Magellanic Cloud (LMC), N49, N49B, N23, and DEM L71, for accurate determination of their plasma state. Our uniform analysis reveals that only N49 is in the recombining state among them, which is the first robust discovery of a RP from an extra-galactic SNR. Given that RPs have been identified only in core-collapse SNRs, our result strongly suggests a massive star origin of this SNR. On the other hand, no clear evidence for a RP is confirmed in N23, from which detection of recombination lines and continua was previously claimed. Comparing the physical properties of the RP SNRs identified so far, we find that all of them are categorized into the "mixed-morphology" class and interacting with surrounding molecular clouds. This might be a key to solve formation mechanisms of the RPs.