Phase-Dependent Spectroscopy of Mira Variable Stars

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Spectroscopic measurements of Mira variable stars as a function of phase probe the stellar atmospheres and underlying pulsation mechanisms. For example, measuring variations in TiO, VO, and ZrO with phase can be used to help determine whether these molecular species are produced in an extended region above the layers where Balmer line emission occurs or below this shocked region. Using the same methods, the Balmer line increment, where the strongest Balmer line at phase zero is Hδ and not Hα, can be measured and explanations tested, along with another peculiarity, the absence of the H∈ line in the spectra of Mira variables when the other Balmer lines are strong. We present new spectra covering the spectral range from 6200 to 9000 Å of 20 Mira variables. A relationship between variations in the Ca II IR triplet and Hα as a function of phase support the hypothesis that H∈'s observational characteristics result from an interaction of H∈ photons with the Ca II H line. New periods and epochs of variability are also presented for each star.