X-Ray Emission from the Wolf-Rayet Bubble S 308
Gruendl, R. A.; Smith, R. C.; Chu, Y. -H.; Guerrero, M. A.; Toalá, J. A.; Snowden, S. L.; Arthur, S. J.
Spain, Mexico, United States
Abstract
The Wolf-Rayet (WR) bubble S 308 around the WR star HD 50896 is one of the only two WR bubbles known to possess X-ray emission. We present XMM-Newton observations of three fields of this WR bubble that, in conjunction with an existing observation of its northwest quadrant, map most of the nebula. The X-ray emission from S 308 displays a limb-brightened morphology, with a central cavity ~22' in size and a shell thickness of ~8'. This X-ray shell is confined by the optical shell of ionized material. The spectrum is dominated by the He-like triplets of N VI at 0.43 keV and O VII at 0.57 keV, and declines toward high energies, with a faint tail up to 1 keV. This spectrum can be described by a two-temperature optically thin plasma emission model (T 1 ~ 1.1 × 106 K, T 2 ~ 13 × 106 K), with a total X-ray luminosity ~2 × 1033 erg s-1 at the assumed distance of 1.5 kpc.
Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.