Hα observations have been made of the stars brighter than mv
= 7.5 and north of δ = −30° contained in the three classical Be-star catalogues of Merrill and Burwell. At least one observation of each star was made at each of the two epochs 1958/9 and 1970/2 at the Lick Observatory and at the Warner and Swasey Observatory respectively. The dispersions used were 88 Å mm−1 at Lick and 66 Å mm−1 and 18 Å mm−1 (with image tube) at Warner and Swasey.
Results were as follows: The total number of objects observed was 215. Of these, 32 were supergiants and will be discussed later. Another 16 stars were deemed abnormal in some manner (helium and/or forbidden emission, composite spectrum, markedly violet-displaced Hα emission component: an interesting group of five stars including the nebular variable AB Aurigae). Thirteen of the stars showed no emission at either epoch. Of the 154 presumably normal low-luminosity stars showing emission, 70 displayed shell structure in Hα at one or both epochs, though in over half of these cases the shell absorption was considered ‘weak’. Thirty of the 70 stars varied in their shell characteristics between the two epochs. The total number of stars whose Hα line varied in some respect was 43, or 26 percent of the 167 normal low-luminosity stars observed. Quite a number of the stars observed have been reported to show shell characteristics by others but were not so noted by us.
Eight additional Be stars not contained in the Merrill-Burwell catalogues have also been observed. Seven of these are shell stars; the other is the unusually high latitude object HD 127617.
It is a pleasure to acknowledge that many of the Lick observations were made by Dr Jack E. Forbes, a graduate student at the time in the Department of Astronomy at the University of California, Berkeley.