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Session 48 - Circumstellar Envelopes.
Display session, Tuesday, January 14
Metropolitan Ballroom,
Observations of circumstellar envelopes around evolved giant stars provide important constraints on models of the late stages of stellar evolution and on the amount of material returned from these stars to the interstellar medium. Millimeter- and submillimeter-wavelength molecular lines are excellent probes of the physical conditions and chemistry of such circumstellar envelopes. In particular, the CO molecule has a high abundance throughout the envelope and its different rotational transitions trace gas at various levels of excitation. Here we report submillimeter observations of the J=6\to5 transition of CO toward o Ceti (Mira), the prototypical Mira variable. We use our data, as well as previously published observations of lower-excitation transitions of CO, as input for model calculations that solve the radiative transfer problem with a Monte Carlo method. We obtain estimates of the mass loss rate, the temperature distribution, and the expansion and turbulent velocity in the envelope.
