Mira ’ s wind explored in scattering infrared CO lines

We have observed the intermediate regions of the circumstellar envelope of Mira (o Ceti) in photospheric light scattered by three vibration-rotation transitions of the fundamental band of CO, from low-excited rotational levels of the ground vibrational state, at an angular distance of β ∼ 2 − 7 away from the star. The data were obtained with the Phoenix spectrometer mounted on the 4 m Mayall telescope at Kitt Peak. The spatial resolution is approximately 0.5 and seeing limited. Our observations provide absolute fluxes, leading to an independent new estimate of the mass-loss rate of approximately 3× 10M⊙ yr, as derived from a simple analytic wind model. We find that the scattered intensity from the wind of Mira for 2 < ∼ β < ∼ 7 decreases as β, which suggests a time constant mass-loss rate, when averaged over 100 years, over the past 1200 years. Subject headings: stars: AGB and post-AGB — circumstellar matter — stars: individual (o Ceti) — stars: late-type — stars: mass loss — infrared: stars