A NEW EJECTA SHELL SURROUNDING A WOLF-RAYET STAR IN THE LMC

We have obtained CCD spectra of newly discovered shell-like nebulae ar ound the WN4 star Breysacher 13 and the WN1 star Breysacher 2 in the L arge Magellanic Cloud. The shell around Br 13 shows definite signs of enrichment in both nitrogen and helium, having much stronger [N II] an d He I emission lines than are seen in typical LMC H II regions. From the measured electron temperature of about 17,000 K in the shell, we d erive He/H and N/O abundance ratios which are factors of 2 and more th an 10 higher, respectively, than the average LMC interstellar values. The derived oxygen abundance in the Br 13 shell is down by a factor of 8 compared to the local LMC ISM; however, the derived electron temper ature is affected by the presence of an incomplete shock arising from die interaction of the stellar wind with photoionized material. This u ncertainty does not affect the basic conclusion that the Br 13 shell i s enriched by processed material from the Wolf-Rayet star. In contrast , the shell around Br 2 shows no clear evidence of enrichment. The neb ular spectrum is characterized by extremely strong [O III] and He II e mission and very weak [N II]. We derive normal He, O, and N abundances from our spectrum. This object therefore appears to be simply a wind- blown structure associated with a relatively dense cloud near the Wolf -Rayet star, although the very high-ionization state of the gas is unu sual for a nebula associated with a Wolf-Rayet star.