The authors have investigated the ultraviolet extinction and element depletions in the circumstellar envelope of the M supergiant binary system, α Sco, by using IUE, Copernicus, and ANS data of the B dwarf companion, α Sco B, which can be seen in absorption through the cool-star envelope. After assessing the interstellar, circumstellar, and atmospheric column densities toward α Sco B, the authors estimated the circumstellar reddening, the circumstellar depletions, and the circumstellar spectral extinction toward α Sco B. It is found that the circumstellar grains in this oxygen-rich environment are larger than 0.05 μm and siliceous in composition, yet contain less depleted elements than the diffuse-interstellar grains in the Scorpius region or the general Galactic diffuse-interstellar grains.
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P. et al. (1987) studied this question.