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# Program information file
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PROGRAM_ID 2024A058
PROGRAM_TITLE IR observations at high spectral resolution of Mira-type variables at different stellar phases - a step towards disentangling the mysteries of the dynamics of the inner molecular shell
PROGRAM_INV1 Guido W. Fuchs
PROGRAM_INV2 Eileen Doering
PROGRAM_INV3 David Gobrecht
PROGRAM_INV4 Thomas K. Greathouse
PROGRAM_INV5 Rohini S. Giles
PROGRAM_SCICAT stellar
PROGRAM_ABSTRACT_BEG
With this project we hope to obtain important observational data for a better understanding of the stellar dynamics of variable stars. The previous TEXES/IRTF observational data have revealed some surprises regarding the internal dynamics and chemistry of the Mira variables chi Cyg, o Cet, R Cas, and IK Tau. Mira-type AGB stars show remarkable mass loss, leading to the formation of molecular layers near the central star and a dusty envelope farther out. With our high-resolution mid-IR data, we have access to important molecular species, like SiO and TiO, that are thought to form close to the star. By covering not one but multiple stellar phases, we can test current circumstellar envelope models and add important insights to studies that have excellent spatial resolution but no time dependence. Here, the mid-IR region around 8 and 10 mu provides an excellent discrimination of background conditions [hot stellar vs. warm dusty shell] based on the observed P-Cyg profile. Previous observations have shown that the line shapes of the molecules change - sometimes significantly - during a stellar period. Tracking these changes leads to a better understanding of the ongoing dynamics and constrains current models. In contrast to previous observations, we plan to extend the frequency range covered to allow for a more precise determination of the physical conditions such as temperature and column density, and also to potentially identify new molecules. Due to the time-limited access [TEXES is mounted on IRTF only two times per semester], there is a need to fill existing gaps in stellar phase coverage to clarify molecular infall and outflow scenarios. Last year, due to problems at the IRTF [temporary shutdown], we missed important phases for Chi Cyg and IK Tau and hope to make up, at least in part, for these missing observations in the coming semester.
PROGRAM_ABSTRACT_END