9. A methodological remark
Waelkens & Rufener (1985) and Waelkens (1991) reported discoveries of multiperiodic light variations of some apparently non-emission B stars, with periods in the range from 0 8 to 4 4. They called them "slowly pulsating B stars or SPB" to distinguish them from Cep variables with much shorter periods ( 0 1 - 0 25). By its period, CMa would also qualify into this category. Clearly, one of the results of this paper represents a methodological warning that the detection of an apparent multiperiodicity with several rather close periods, typical not only for the SPB stars but also for the Cep stars and some other Be stars (cf., e.g., µ Cen: Rivinius et al. 1998) should also be tested against the hypothesis of a single and slowly periodically variable period. This is even more desirable after the finding that a number of the Cep and SPB stars are members of binary or multiple systems of stars (cf., e.g., Pigulski & Boratyn 1992, Aerts et al. 1998) since for such stars the slow periodic variations of the principal period of oscillation due to the light-time effect do inevitably occur. More generally, one should realize that many Fourier terms would be needed for a complete description of the very complicated signal which one observes in situations like this one.
© European Southern Observatory (ESO) 1998
Online publication: May 15, 1998