HST/GHRS Study of $\zeta$ Aurigae \\ III. The Ionization Structure of the Wind of $\zeta$~Aur A (K4 Ib)
Session 18 -- Stellar Spectra: Individual Objects
Display presentation, Wednesday, January 12, 9:30-6:45, Salons I/II Room (Crystal Gateway)

## [18.10] HST/GHRS Study of $\zeta$ Aurigae \\ III. The Ionization Structure of the Wind of $\zeta$~Aur A (K4 Ib)

Graham M. Harper, Philip D. Bennett, Alexander Brown, Jeffrey L. Linsky (JILA, U. Colorado \& NIST)

We present models of the ionization structure of the K4 Ib star wind in the binary system $\zeta$~Aurigae for the epochs corresponding to the Hubble Space Telescope (HST) observations of the 1993 eclipse.

We have modeled the atmospheric density structure using a description of the winds from both components of the binary system. New models of the K star chromosphere and wind are used to constrain the electron temperatures and electron densities. Thermodynamic properties from these atmospheric models combined with the radiation fields from both stellar components have then been used to model the ionization balance of H~I/H~II, Fe~I/Fe~II/Fe~III and Si~I/Si~II/Si~III. These ionization models represent the first stage in interpreting the new HST observations. The column densities deduced from selected absorption features can then be used to derive new estimates of the density and temperature structure in the K star wind.

This work is supported by HST Grant GO-3626.01-91A to the University of Colorado.