Drake AAS Presentation

Imaging and Kinematics of Multiple Ring Nebulae Around Wolf-Rayet Stars in M33

L. Drissen, Dept. de Physique, U. Laval, St. Foy, PQ, G1K 7P4, Canada

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Abstract

The study of circumstellar materials around evolved massive stars leads to the possibility of obtaining information on the history of such stars. In particular, Wolf-Rayet stars are believed to have evolved from massive ($>$25$M_{\odot}$) O star progenitors via a phase of major mass loss (such as a red supergiant or luminous blue variable). The morphology and kinematics of ejected materials may be expected to provide information on the amount of and timescale for mass-loss. In particular, the existence of multiple shells around Wolf-Rayet stars enables the study of the effects of different phases of mass loss. We present high resolution imaging and Fabry-Perot observations, made at the Canada-France-Hawaii Telescope (CFHT), of multiple ring nebulae around Wolf-Rayet in the nearby galaxy M33. These show the existence of ejecta shells inside of main sequence shells O star cavities, some of which are almost the same size, suggesting ejecta expansion is not necessarily stalled by the hot interior of the progenitor O star bubble. H$\alpha$ and [OIII] kinematics are often dramatically different. Our H$\alpha$ kinematics suggest that regions of enhanced [OIII] emission are almost exclusively associated with fast-moving Wolf-Rayet wind-blown bubbles inside ejecta materials. Regions of enhanced [OIII] emission appear around WN rather than WC subclasses of Wolf-Rayet stars, suggesting "blowouts" of the Wolf-Rayet blown winds towards the end of the WN phase and prior to the WC phase. WC nebulae are larger than WN nebulae which is consistent with the evolution of Wolf-Rayet stars from WN to WC.

This work was funded in part by NASA ADP grant NAG5-2999 and a grant from NASA administered by the American Astronomical Society

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