Suzaku study on the Ejecta of the Supernova Remnant G272.2$-$3.2

TL;DR

This study re-analyzes Suzaku X-ray data of SNR G272.2-3.2, revealing detailed ejecta composition and shock heating features, especially the presence of Fe K-shell lines, indicating recent reverse shock heating typical of Type Ia supernova remnants.

Contribution

It provides a detailed spectral analysis above 3 keV, identifying ejecta origin and shock heating processes not previously characterized in this remnant.

Findings

Detection of Ar, Ca, and Fe K-shell lines above 3 keV.

Identification of two plasma components: CIE and NEI.

Ejecta are recently heated by reverse shock, indicated by Fe line energy.

Abstract

We report re-analyses of the Suzaku observations of the Galactic supernova remnant (SNR), G272.2$-$3.2, for which the previous studies were limited below 3 keV. With careful data reduction and background subtraction, we discover the K-shell lines of Ar, Ca, and Fe above 3 keV. The X-ray spectrum of G272.2$-$3.2 consists of two components, a low-temperature collisional ionization equilibrium (CIE) plasma ($kT_{\rm e} \sim 0.2$ keV) and a high-temperature non-equilibrium ionization (NEI) plasma ($kT_{\rm e} = 0.6$-$3$ keV). The CIE plasma has solar abundances over the entire area, hence it would originate from the interstellar medium. On the other hand, the abundances of the NEI plasma increase toward the inner region, suggesting the ejecta origin. The line center energy of the Fe K-shell emission ($\sim 6.4$ keV) suggests that the ejecta are recently heated by the reverse shock, a common feature in Type Ia SNRs.