AAS 199th meeting, Washington, DC, January 2002
Session 90. $\delta$ Scuti and Mira Variables
Display, Wednesday, January 9, 2002, 9:20am-6:30pm, Exhibit Hall

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[90.08] Modeling Phase-Resolved Spectra of Mira Variables

M. Y. Woo (Cornell Univ.), A. Schweitzer (Univ. of Georgia), M. W. Castelaz (Pisgah Astronomical Research Inst.)

Based on the stellar atmosphere code PHOENIX we created a grid of spherical symmetric model atmospheres suitable for one solar mass Miras. They include our latest molecular opacity sources and dust formation treatment. The parameters of the grid range from T\rm eff=2400~K to 3700~K and from \log(g)=1.0 to 2.0. In the first generation of models for Miras they treat the photosphere statically and in LTE.

We used this grid to reproduce phase-resolved low resolution optical spectra of the three Mira variables R~Leo, R~CVn and V~CVn. We have determined effective temperature variations with phase. R~Leo varies from 2400 to 3100~K, V~CVn from 3400 to 3600~K and R~CVn from 2800 to 3600~K. The changes in \log(g) are too small to resolve. The spectral regions which vary from cycle to cycle cannot be reproduced. This is most likely due to dynamical effects. This grid will be the foundation to create non-LTE models including winds in order to reproduce the phase resolved behavior of Mira spectra including the behavior of the Balmer and Ca emission lines.

This work was funded by the NSF REU grant AST-0097616 to the Southeastern Association for Research in Astronomy (SARA) and by NASA ATP grant NAG 5-8425 to the University of Georgia. Some of the calculations were performed on the IBM SP2 of the UGA UCNS, on the IBM SP ``Blue Horizon'' of the San Diego Supercomputer Center, with support from the NSF, and on the IBM SP of the NERSC with support from the DoE.

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