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Session 103 - Cool Stars.
Display session, Thursday, January 18
North Banquet Hall, Convention Center

[103.04] The Chromosphere and Wind of \zeta Aurigae

P. D. Bennett, A. Brown (CASA, U. of Colorado at Boulder), G. M. Harper, N. Piskunov (JILA), R. E. M. Griffin (U. of Cambridge)

The \zeta Aurigae binary systems consist of evolved supergiants which eclipse their early-type main sequence companions. These binaries have been extensively studied because of their potential for probing the outer atmospheric structure of the evolved late-type primary. This technique is extremely advantageous in the ultraviolet where the cool primary contributes little flux. To this end, we have undertaken an analysis of the chromosphere and wind of the prototype system, \zeta Aurigae, and we graphically demonstrate the resulting model by means of a video presentation.

Our atmospheric model of the chromosphere and wind of the primary star of \zeta Aurigae (K4 Ib + B5 V) is based on Cycle 2 and recent Cycle 5 observations obtained with the Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope, and on archival IUE and optical spectra. The models were iterated to reproduce the observed circumstellar absorption line curves of growth, and individual absorption profiles, for various projected heights above the limb of the K supergiant. To conveniently show the variation of typical line profiles computed with this model, we have prepared a video that follows the \zeta Aurigae binary system through a complete orbit. We display several windows showing a perspective view of the system from a vantage point above the orbital plane, the view as seen from earth (nearly edge-on, i=87.3^\circ ), and the behavior of absorption lines formed in the chromosphere and wind of \zeta Aurigae as a function of orbital phase.

Support for this work was provided by NASA through grants GO-3626-91A and GO-06069.01-94A from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Program listing for Thursday