X-RAY EMISSION FROM THE WOLF-RAYET BUBBLE S 308

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 OVII 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 sub(1) ~ 1.1 x 10 super(6) K, T sub(2) ~ 13 x 10 super(6) K), with a total X-ray luminosity ~2 x 10 super(33) erg s super(-1) at the assumed distance of 1.5 kpc.