NOTES ON STELLAR SPECTRA

Abstract

Phi Persei. This star has a well-known helium-shell spectrum, with He i 3965 sharp, while those lines which have nonmetastable lower levels are usually broad and shallow. The H lines show absorption cores between broad emission wings. Several spectrograms, obtained on October 22, 1951, with the coude spectrograph of the Mount Wilson 100-inch telescope show that He i 3888 and He i 3188 (23S n3P°) also have strong absorption cores. But while the //-cores are distinctly unsymmetrical, or even double, being shaded shortward, the He cores are nearly symmetrical. Especially interesting is an exceedingly narrow, deep, absorption line which is centrally superposed over the normal absorption core of He i 3888. This feature has not been seen previously since it requires a dispersion of at least 10 A/mm. Its width is so small that it must come from an even higher layer than the rest of the He and H shell spectrum. Rotation, which at the normal shell level is sufficient to appreciably broaden the cores of many lines, is negligible at the height where the very narrow line originates. Moreover, turbulence at this high level is also negligible : it must be less than 2 or 3 km/sec, resembling in this respect the conditions within interstellar gas clouds. Since there is strong independent evidence that at more moderate heights, within extended stellar atmospheres, the turbulence at first increases with the height, we must now conclude that at still higher elevations it decreases. The H absorption cores are not very strong and can be seen as distinct, narrow lines only to H 14. Beyond this limit there are a few diffuse absorption features which probably result from the overlapping of broad underlying hydrogen lines. Even these disappear long before the Balmer limit is reached. AR Lacertae. The discovery of double absorption lines in the s Canis Ma joris stars, 12 Lacertae and o Scorpii, has led to