X-ray emission from the Wolf-Rayet bubble NGC 6888. II. XMM-Newton EPIC observations

Abstract

We present deep XMM-Newton EPIC observations of the Wolf-Rayet (WR) bubble NGC6888 around the star WR136. The complete X-ray mapping of the nebula confirms the distribution of the hot gas in three maxima spatially associated with the caps and northwest blowout hinted at by previous Chandra observations. The global X-ray emission is well described by a two-temperature optically thin plasma model $T_1$=1.4$\times$10${}^6$ K, $T_2$=8.2$\times$10${}^6$ K) with a luminosity of $L_{\mathrm{X}}$=7.8$\times$10${}^{33}$ erg s${}^{-1}$ in the 0.3--1.5 keV energy range. The rms electron density of the X-ray-emitting gas is estimated to be $n_{\mathrm{e}}$=0.4 cm${}^{-3}$. The high-quality observations presented here reveal spectral variations within different regions in NGC6888, which allowed us for the first time to detect temperature and/or nitrogen abundance inhomogeneities in the hot gas inside a WR nebula. One possible explanation for such spectral variations is that the mixing of material from the outer nebula into the hot bubble is less efficient around the caps than in other nebular regions.

10 pages, 4 figures, 2 tables; Accepted to MNRAS

References in corpus (9)

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• X-ray Emission from the Wolf-Rayet Bubble NGC 6888. I. Chandra ACIS-S Observations
• The Trace of the CNO Cycle in the Ring Nebula NGC6888
• Herschel-PACS Measurements of Nitrogen Enrichment in Nebulae around Wolf-Rayet Stars
• A Consistent Spectral Model of WR 136 and its Associated Bubble NGC 6888

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• Unveiling the stellar origin of the Wolf-Rayet nebula NGC6888 through infrared observations
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• Momentum and energy injection by a wind-blown bubble into an inhomogeneous interstellar medium
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