On the presence of OI lambda 1302 emission in Be stars.

Abstract

The absence of UV O I emission from Be stars is investigated in terms of a model for a circumstellar disk. Observations of the O I 8446 A transition are shown to produce the UV O I triplet 1302.17, 1304.86, and 1306.02 A, which has not been seen. It is demonstrated that the total scattering optical depth in the circumstellar gas is sufficient to ensure that most photons arising from the O I 8446 A transition will be destroyed in an envelope with a density of 10 to the 12th electrons/cu cm, such as has been projected for Be stars. It is also mentioned that a flattened Be star envelope will, if viewed equator-on, will scatter more 1302 A photons from the line-of-sight, implying that Be stars observed pole-on would exhibit an enhanced 1302 A emission because the photons are scattered perpendicularly from the flattened, equatorial disk.