On the Classification of Stars of the & Cephei Class, 447 



Stars resembling 7 Cygni formed the sub-group III/3. 



In November, 1895, I gave an account* of the spectra of five short 

 period variable stars, 8 Cephei, rj Aquilae, £" Geminorum, T Vul- 

 peculee, and S Sagittse, and pointed out that these belonged to the 

 same sub-group as 7 Cygni, which, however, is not a variable star ; 

 a Ursse Minoris has also a spectrum which has since been recognised 

 to be identical with that of 7 Cygni and S Cephei, while a, Persei 

 differs so slightly from them that it may also be classified with 

 thetn. 



These I now group together, and for convenience of reference I 

 designate them the & Cephei class. 



Dr. VogeVs Classification. 



Only two of the stars which have been mentioned as belonging to 

 the h Cephei class, namely, // Aquilse and S(10) Sagittse, were 

 included in Vogel's spectroscopic Durchmusterung, published in 1883, 

 and both are classed without further comment as stars of Class Ila.f 

 This type of spectrum was thus defined : " Spectra with very numer- 

 ous metallic lines, which are easily known by their intensity, espe- 

 cially in the yellow and green. The hydrogen lines are for the most 

 part strong, but are never so broad as in the case of Class la. In 

 some stars the lines of hydrogen are faint, and in these faint bands 

 can be generally recognised in the less refrangible portion of the 

 spectrum." 



So far as Vogel's classification serves as a guide, then, all the stars 

 of the B Cephei class would be classed with the sun. 



Dr. Scheiner has discussed one of the stars of the 8 Cephei class, 

 ol Persei, in some detail. J Attention is specially drawn by him to 

 the differences between the spectrum of a Persei and that of the 

 sun. 



In the following table I have brought together the lines of « Persei 

 which Dr. Scheiner states to be more intense than in the sun, and 

 have compared them with h Cephei and a Cygni as photographed at 

 Kensington. The remarks in the last column are those made by 

 Dr. Scheiner with regard to the spectrum of a Persei. 



* 1 Roy. Soc. Proc.,' vol. 59, p. 103. 



f ' Public. Astr. Obs. zu Potsdam,' vol. 3, p. 200. 



X 1 Public. Astr. Obs. zu Potsdam,' vol. 7, Part II, p. 329. 



