WR bubbles and HeII emission

Abstract

We present the very first high quality images of the HeII 4686 emission in three high excitation nebulae of the Magellanic Clouds. A fourth high excitation nebula, situated around the WR star BAT99-2, was analysed in a previous letter. Using VLT FORS data, we investigate the morphology of the ring nebulae around the early-type WN stars BAT99-49 & AB7. We derive the total HeII fluxes for each object and compare them with the most recent theoretical WR models. Using Halpha, [OIII] and HeI 5876 images along with long-slit spectroscopy, we investigate the physical properties of these ring nebulae and find only moderate chemical enrichment. We also surveyed seven other LMC WR stars but we failed to detect any HeII emission but note that the nebula around BAT99-11 shows a N/O ratio and an oxygen abundance slightly lower than the LMC values, while the nebula around BAT99-134 presents moderate chemical enrichment similar to the one seen near BAT99-2, 49 and AB7. The third high excitation nebula presented in this paper, N44C, does not harbor stars hotter than mid-O main sequence stars. It was suggested to be a fossil X-ray nebula ionized but our observations of N44C reveal no substantial changes in the excitation compared to previous results reported in the literature.

13 pages, 8 figures (7 in jpg), accepted by A&A, also available from http://vela.astro.ulg.ac.be/Preprints/P81/index.html

References in corpus (7)

• Realistic Ionizing Fluxes for Young Stellar Populations from 0.05 to twice solar metallicity
• Stellar and Wind Properties of LMC WC4 stars - A metallicity dependence for Wolf-Rayet mass-loss rates
• Interstellar Bubbles in Two Young HII Regions
• HST observations of the LMC compact HII region N11A
• Structure and Dynamics of Candidate O Star Bubbles in N44
• VLT observations of the highly ionized nebula around Brey2
• The Massive Wolf-Rayet Binary SMC WR7

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• On the contribution of the X-ray source to the extended nebular HeII emission in IZw18
• Keck Cosmic Web Imager Observations of He II Emission in I Zw 18
• Discovery of a new Wolf-Rayet star and a candidate star cluster in the Large Magellanic Cloud with Spitzer
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• Spitzer and Herschel studies of dust in supernova remnants in the Small Magellanic Cloud
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• The highly ionized, high velocity gas in NGC 6231