Sensitive VLA observations of the evolved stars α Ori and IRC +10216 have resulted in the detection of 21 cm H I emission from the envelope formed by mass loss from α Ori. The data are subject to difficulties and uncertainties caused by the strong galactic H I line in this direction; the observed H I flux gives a mass-loss rate of ≡2.2×10-6(D/200 pc)2M_sun; yr-1 and an envelope radius of ≡1arcmin(1.8×1017cm at D = 200 pc). Comparison with molecular line, infrared, radio continuum, and optical data shows that the gas-to-dust ratio in the circumstellar outflow has ≡10 - 20 times the interstellar value. No H I emission was detected from IRC +10216. The implications of these results for circumstellar and interstellar chemistry are discussed.
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Bowers et al. (1987) studied this question.