Diffuse X-ray Emission within Wolf-Rayet Nebulae

TL;DR

This paper reviews recent X-ray observations of Wolf-Rayet nebulae, revealing common characteristics such as plasma temperature, confined diffuse emission, and specific luminosities, indicating mixing or thermal conduction processes.

Contribution

It provides a comparative analysis of X-ray properties across multiple Wolf-Rayet nebulae, highlighting their shared features and possible physical mechanisms.

Findings

Plasma temperatures are around 1-2 million Kelvin.

Diffuse X-ray emission is confined within the nebulae's optical shells.

X-ray luminosities are approximately 10^{33} to 10^{34} erg/s.

Abstract

We discuss our most recent findings on the diffuse X-ray emission from Wolf-Rayet (WR) nebulae. The best-quality X-ray observations of these objects are those performed by XMM-Newton and Chandra towards S308, NGC2359, and NGC6888. Even though these three WR nebulae might have different formation scenarios, they all share similar characteristics: i) the main plasma temperatures of the X-ray-emitting gas is found to be $T$=[1-2]$\times$10$^{6}$ K, ii) the diffuse X-ray emission is confined inside the [O III] shell, and iii) their X-ray luminosities and electron densities in the 0.3-2.0~keV energy range are $L_\mathrm{X}\approx$10$^{33}$-10$^{34}$~erg~s$^{-1}$ and $n_\mathrm{e}\approx$0.1-1~cm$^{-3}$, respectively. These properties and the nebular-like abundances of the hot gas suggest mixing and/or thermal conduction is taking an important role reducing the temperature of the hot bubble.