[Previous] | [Session 135] | [Next]
J.D.T. Smith (Cornell University)
The fast, dense winds which characterize Wolf-Rayet (WR) stars obscure their underlying cores, and complicate the verification of evolving core models. A powerful technique for probing WR core evolution involves measuring abundances of wind-borne nuclear processed elements. Neon in particular undergoes a remarkable abundance change during the later stages of a WR star's lifetime. By the end of carbon (WC) phase, it becomes the fourth most abundant element (after He, C and O).
Using ground-based mid-infrared spectroscopy and the 12.8\mu m [Ne\,\textsc{ii}] emission line measured in four galactic WR stars, we estimate neon abundance and compare to long-standing predictions from evolved-core models. For the WC star WR\,121, this abundance is found to be ~ 7\times the cosmic value, in good agreement with predictions. For the three less evolved nitrogen (WN) stars with measured [Ne\,\textsc{ii}], no neon enhancement above cosmic values is measured, as expected.
We discuss the impact of clumping in WR winds on this measurement, and the promise of using metal abundance ratios to eliminate sensitivity to wind density and ionization structure.
The author(s) of this abstract have provided an email address for comments about the abstract: jdsmith@astro.cornell.edu