On the diffuse X-ray emission from the Wolf-Rayet Bubble NGC 2359

TL;DR

This study reanalyzed XMM-Newton X-ray data of NGC 2359, revealing diffuse emission with two temperature components, similar chemical abundances to the optical nebula, and evidence of material mixing in the hot bubble.

Contribution

It provides an improved analysis of X-ray emission from NGC 2359, clarifying plasma properties and chemical abundances, and highlighting the presence of a blowout and material mixing.

Findings

Diffuse X-ray emission detected in NGC 2359.

Two plasma temperature components identified.

Chemical abundances similar to optical nebula.

Abstract

A recent XMM-Newton observation (Zhekov 2014) has revealed diffuse X-ray emission inside the nebula NGC 2359 around the Wolf-Rayet star WR 7. Taking advantage of an improved point-source rejection and background subtraction, and a detailed comparison of optical and X-ray morphology, we have reanalyzed these X-ray observations. Our analysis reveals diffuse X-ray emission from a blowout and the presence of emission at energies from 1.0 to 2.0 keV. The X-ray emission from NGC 2359 can be described by an optically-thin plasma emission model, but contrary to previous analysis, we find that the chemical abundances of this plasma are similar to those of the optical nebula, with no magnesium enhancement, and that two components at temperatures T_1=2x10^6 K and T_2=5.7x10^7 K are required. The estimated X-ray luminosity in the 0.3 - 2.0 keV energy range is L_X=2x10^33 erg s^-1. The averaged rms electron density of the X-ray-emitting gas (n_e \lesssim 0.6 cm^-3) reinforces the idea of mixing of material from the outer nebula into the hot bubble.