Discovery of recombining plasma associated with the candidate supernova remnant G189.6+3.3 with Suzaku

TL;DR

This study reports the first detection of recombining plasma in the supernova remnant G189.6+3.3 using Suzaku, revealing new insights into its ionization state and composition.

Contribution

First identification of recombining plasma in G189.6+3.3 through X-ray spectral analysis, expanding understanding of supernova remnant plasma states.

Findings

Detection of K-shell lines from highly ionized elements.

Clear observation of radiative recombining continuum from He-like Si.

G189.6+3.3 is likely a middle-aged SNR with recombining plasma.

Abstract

We present the results of an X-ray spectral analysis of the northeast region of the candidate supernova remnant G189.6+3.3 with Suzaku. K-shell lines from highly ionized Ne, Mg, Si, and S were detected in the spectrum for the first time. In addition, a radiative recombining continuum (RRC) from He-like Si was clearly seen near 2.5 keV. This detection of an RRC reveals for the first time that G189.6+3.3 possesses an X-ray-emitting recombining plasma (RP). The extracted X-ray spectrum in the 0.6-10.0 keV energy band is well fitted with a model consisting of a collisional ionization equilibrium plasma component (associated with the interstellar medium) and an RP component (associated with the ejecta). The spectral feature shows that G189.6+3.3 is most likely to be a middle-aged SNR with an RP.