Narrow-band photometry of bright Be stars

Narrow-band photometry centered at the H-alpha and H-beta Balmer lines is used to separate emission from nonemission stars in a sample of early-type stars, and to examine possible variations in the hydrogen emission-line strengths of some bright Be stars. In the sample of 36 bright early-type stars having previously shown Balmer emission lines, five are found to satisfy a relation between the alpha and beta indices in the Porto Alegre and Crawford and Mander systems, respectively, characteristic of normal B stars, indicating a lack of emission, at least at the time of the present observations. The nonemission status of these stars is also confirmed by the variation of their Balmer decrement with alpha index. Comparison of the present alpha indices of 26 program stars with those recorded eight years previously by Feinstein (1974) reveal variations greater than 0.05 in the alpha indices, very likely due to changes in emission line strength.