"An Interstellar Conduction Front Within a Wolf-Rayet Ring Nebula Observed with the GHRS"

Bram Boroson, Richard McCray, Christina Oelfke Clark JILA, University of Colorado
Jonathan Slavin NASA Goddard Space Flight Center
Mordecai-Mark Mac Low Max-Planck-Institut für Astronomie
You-Hua Chu University of Illinois
Dave Van Buren IPAC, California Institute of Technology

With the High Resolution Spectrograph aboard the Hubble Space Telescope we obtained high signal-to-noise (S/N > 200 - 600 per 17 km/s resolution element) spectra of narrow absorption lines toward the Wolf-Rayet star HD 50896. The ring nebula S308 that surrounds this star is thought to be caused by a pressure-driven bubble bounded by circumstellar gas (most likely from a red supergiant or luminous blue variable progenitor) pushed aside by a strong stellar wind. Our observation has shown for the first time that blueshifted (~70 km/s relative to the star) absorption components of C IV and N V arise in a conduction front between the hot interior of the bubble and the cold shell of swept-up material. These lines set limits on models of the conduction front. Nitrogen in the shell appears to be overabundant by a factor ~10. The P Cygni profiles of N V and C IV are variable, possibly due to a suspected binary companion to HD 50896.

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Mordecai-Mark Mac Low, mordecai@mpia-hd.mpg.de
Last modified: Mon Nov 4 10:20:21 MET 1996