Stars whose Spectra have Bright H and K Lines of Calcium.

Stars whose spectra are known to show the H and K lines of Caii in emission are listed in Table 1, together with the first published reference to their discovery. The intensities were estimated from Mount Wilson spectrograms. In general, the supergiants and giants show the 113 and K3 reversals, whereas the subgiants and main-sequence stars have fairly sharp, single, emission lines. The strength of the bright lines in any star appears, at present, to be unpredictable; variation in intensity is suspected in many stars. Emission of Ca ii seldom occurs in stars hotter than G5