7. Discussion and conclusions
The discovery of Cephei pulsations in Oo 692 and Oo 992, the two early B-type stars located in the central region of h Persei, together with our findings described in Paper I mean, that the double cluster h and Persei is indeed rich in these kind of variables. Since our up-to-date observations were confined to the central regions of the double cluster, more stars of this type may be discovered. Regarding the richness of h and Persei, we estimated that the clusters should contain about 10-15 Cephei stars. Candidates have already been selected and observations of other fields in both clusters are now under way.
Another interesting discovery in h Persei is finding of
SPB-type variations in Oo 893. Although the star is monoperiodic
within the detection limit of our observations, the distinct
wavelength dependence of the amplitude of variations is a strong
argument in favour of an SPB classification. Many monoperiodic stars
found in the HIPPARCOS data (Waelkens et al. 1998) were
also classified as SPBs. It seems, therefore, that multiperiodicity
cannot be longer regarded as a necessary condition for classifying a
star as an SPB. Consequently, some of the monoperiodic variables found
by Balona and co-workers in three southern young open clusters (Balona
1994; Balona & Koen 1994; Balona & Laney 1994) could be, in
fact, SPB stars.
© European Southern Observatory (ESO) 1999
Online publication: April 19, 1999