The Plasma Structure of the Southwestern Region of the Cygnus Loop with the XMM-Newton Observatory

TL;DR

This study uses XMM-Newton observations to analyze the plasma structure of the Cygnus Loop's southwestern region, revealing details about ejecta and interstellar medium components, and suggesting a core-collapse supernova origin.

Contribution

First detailed X-ray analysis of the Cygnus Loop's 'blow-out' region, clarifying plasma components and ruling out an additional supernova remnant.

Findings

Ejecta component has a temperature of ~0.4 keV, originating from the supernova ejecta.

Interstellar medium component has a temperature of ~0.2 keV, indicating a thin swept-up medium.

The Cygnus Loop likely resulted from a core-collapse supernova explosion.

Abstract

We observed the southwestern region of the Cygnus Loop in two pointings with \textit{XMM-Newton}. The region observed is called the "blow-out" region that is extended further in the south. The origin of the "blow-out" is not well understood while it is suggested that there is another supernova remnant here in radio observation. To investigate the detail structure of this region in X-ray, we divided our fields of view into 33 box regions. The spectra are well fitted by a two-component nonequilibrium ionization model. The emission measure distributions of heavy elements decrease from the inner region to the outer region of the Loop. Then, we also divided our fields of view into 26 annular sectors to examine the radial plasma structure. Judging from metal abundances obtained, it is consistent with that the X-ray emission is the Cygnus Loop origin and we concluded that high-$kT_{e}$ component ($\sim$0.4 keV) originates from the ejecta while low-$kT_{e}$ component ($\sim$0.2 keV) is derived from the swept-up interstellar medium. The flux of low-$kT_{e}$ component is much less than that of high-$kT_{e}$ component, suggesting the ISM component is very thin. Also, the relative abundances in the ejecta component shows similar values to those obtained from previous observations of the Cygnus Loop. We find no evidence in X-ray that the nature of the "blow-out" region originated from the extra supernova remnant. From the ejecta component, we calculated the masses for various metals and estimated the origin of the Cygnus Loop as the core-collapse explosion rather than the Type Ia supernova.