Absolute ultraviolet spectrophotometry with the TD-1 satellite. XI.

Abstract

Low resolution S 2/68 observations are used to show that Be stars of spectral type B0-B5 have a deficiency of ultraviolet radiation (at 2100 A) as compared to the visible with respect to normal stars of the same spectral type. The deficiency is statistically correlated with the strength of visual emission lines, with the existence of an infrared excess and with the presence of a shell. Comparison criteria for Be and B stars are discussed along with the relation between the interstellar color excess and the depth of the 2200 A absorption feature for normal B stars. In addition, the origin of the flux deficiency is considered, and it is shown that the stars with a shell of hydrogen and metals (a strong shell) have a source of absorption different from that of the Be stars with strong emission.