454 On the Classification of Stars of the 8 Cephei Class. 



J^Tame 



Period. 



Interval from 

 min. to max. 



V aliaUKJIl. 







d. h. 



d. h. 









^ Q 



O V 



X It) 





Very regular. 



£ Geminorum .... 



10 4 



5 



3 .y 4 .5 



Period slowly 











1 An nrf n on irtrr 

 1 c 1 1 g Lll t? U 1 U g • 



A -1 









Slightly irregular. 



S(10) Sagittae .... 



8 9 



3 10 



5/6—6 -4 



T Yulpeculse .... 



4 10 



1 7 



5 -5—6 -5 









(1 -7-5-0) 







331 



•• { 













(8 -7—9 -5) 





It will be seen that the luminosity at maximum is from about two 

 (0'8 magnitude) to three times (1*2 magnitudes) greater than at 

 minimum, while the forms of most of the light curves resemble the 

 majority of those of the Mira class in the relatively steep ascent to 

 maximum. A constitution more or less similar to that of the Mira 

 class is therefore indicated. 



I have already shown that in such variables as Mira the presence 

 of bright carbon flutings indicates a meteoritic structure.* Here the 

 variation has a much longer period than in 8 Cephei, but it is only 

 necessary to suppose that 8 Cephei is more condensed, so that revolv- 

 ing swarms of short period will be alone effective in producing 

 collisions at periastron, as I pointed out in 1889. f 



A recent discussion of all the available observations of rj Aquilae 

 by Dr. William J. S. LockyerJ has shown that the light curve of 

 this variable can be best explained on the supposition of three 

 meteor swarms moving around their centre of gravity. In this 

 way not only is the general form of the light curve satisfied, but 

 the smaller irregularities discovered by the author are also easily 

 accounted for. 



Hence, by placing stars of the 8 Cephei class on the ascending 

 arm of the temperature curve, the variability of certain members 

 of the group finds a ready explanation. I am not aware of any satis- 

 factory explanation of the 8 Cephei type of variability in which a 

 constitution resembling that of the sun is assumed, and to my mind 

 such a variation in a star constituted like the sun is impossible. 



* * Roy. Soc. Proc' (1887), vol. 43, p. 130. 

 f ' Roy. Soc. Proc.,' vol. 46, p. 420. 



+ 1 Eesultate aus den Beobaehtungen des veranderlichen Sternes t] Aquilae' 

 (Inaugural-Dissertation, Grottingen, 1897). 



