Hot gas in the Wolf-Rayet nebula NGC3199

TL;DR

This study reports the detection of extended X-ray emission from the Wolf-Rayet nebula NGC3199, revealing complex chemical variations and the influence of the stellar wind from WR18, which is not a runaway star.

Contribution

First XMM-Newton detection of X-ray emission in NGC3199, showing detailed chemical and physical properties of the nebula and clarifying the star's motion status.

Findings

X-ray emission is brighter southeast of WR18.

Regions near the optical arc are nitrogen-rich due to stellar wind.

Gas at the eastern region shows nebular abundances, indicating mixing.

Abstract

The Wolf-Rayet (WR) nebula NGC3199 has been suggested to be a bow shock around its central star WR18, presumably a runaway star, because optical images of the nebula show a dominating arc of emission south-west of the star. We present the XMM-Newton detection of extended X-ray emission from NGC3199, unveiling the powerful effect of the fast wind from WR18. The X-ray emission is brighter in the region south-east of the star and analysis of the spectral properties of the X-ray emission reveals abundance variations: i) regions close to the optical arc present nitrogen-rich gas enhanced by the stellar wind from WR18 and ii) gas at the eastern region exhibits abundances close to those reported for nebular abundances derived from optical studies, signature of an efficient mixing of the nebular material with the stellar wind. The dominant plasma temperature and electron density are estimated to be $T\approx1.2\times$10$^{6}$ K and $n_\mathrm{e}$=0.3 cm$^{-3}$ with an X-ray luminosity in the 0.3-3.0 keV energy range of $L_\mathrm{X}$=2.6$\times$10$^{34}$ erg s$^{-1}$. Combined with information derived from Herschel and the recent Gaia first data release, we conclude that WR18 is not a runaway star and the formation, chemical variations, and shape of NGC3199 depend on the initial configuration of the interstellar medium.