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| Paper: |
Phase Dependent Spectroscopy of Mira Variables |
| Volume: |
154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop |
| Page: |
1586 |
| Authors: |
Castelaz, Michael W.; Luttermoser, Donald G. |
| Abstract: |
Spectroscopic measurements of Mira variable stars, as a function of phase, probe the stellar atmospheres and underlying pulsation mechanisms. Modeling the atmospheres is difficult due to the hydrodynamic nature of the gas as deduced from the large light variations and velocity measurements of various spectral lines. Many questions still need to be resolved concerning the atmospheres of these stars. Are the depths of formation of the molecular species such as TiO, VO, and ZrO produced in an extended region above the layers where Balmer line emission occurs or below this shocked region? What is the explanation for the Balmer-line increment, where the strongest Balmer line at phase zero is Hdelta and not Hα? Furthermore, why is the Hepsilon line virtually absent in the spectra of Miras when the other Balmer lines are strong? We present results from a new program of low resolution (1.08 AA/pixel) spectroscopy of Mira variables from about 6000 AA to 8750 AA. The spectra are taken in a region which includes Hα, TiO, VO, ZrO, and the Ca 2 infrared (IR) triplet. Spectra of a dozen Mira variables observed at more than one phase are presented. We investigate the final question listed above by noting variations in the Ca 2 IR triplet in relationship with Hα variations as a function of phase. These preliminary observations suggest that Hepsilon's observational characteristics result from an interaction of Hepsilon photons with the Ca 2 H line. |
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