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Hot Gas in the Circumstellar Bubble S308

Y. -H. Chu·M. A. Guerrero·R. A. Gruendl·G. Garcia-Segura·H. J. Wendker
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Abstract

S308 is a circumstellar bubble blown by the WN4 star HD50896. It is one of the only two single-star bubbles that show detectable diffuse X-ray emission. We have obtained XMM-Newton EPIC observations of the northwest quadrant of S308. The diffuse X-ray emission shows a limb-brightened morphology, with a clear gap extending from the outer edge of the diffuse X-ray emission to the outer rim of the nebular shell. The X-ray spectrum of the diffuse emission is very soft, and is well fitted by an optically thin plasma model for a N-enriched plasma at temperatures of ~1.1x10^6 K. A hotter gas component may exist but its temperature is not well constrained as it contributes less than 6% of the observed X-ray flux. The total X-ray luminosity of S308, extrapolated from the bright northwest quadrant, is <=(1.2+-0.5)x10^{34} ergs/s. We have used the observed bubble dynamics and the physical parameters of the hot interior gas of S308 in conjunction with the circumstellar bubble model of Garcia-Segura & Mac Low (1995) to demonstrate that the X-ray-emitting gas must be dominated by mixed-in nebular material.

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Y. -H. Chu, M. A. Guerrero, R. A. Gruendl, G. Garcia-Segura, H. J. Wendker. 2003-09-05. Hot Gas in the Circumstellar Bubble S308. https://doi.org/10.1086/379607

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