We have presented new yb photometric observations of V 1162 Ori, and we have shown that the star undergoes frequent period- and amplitude changes on a short time scale. The apparent abrupt nature of the period changes suggests a non-evolutionary origin. The cause of such period changes is presently not known, but it could be non-linear mode interactions (Breger & Pamyatnykh 1998). We do not see evidence for more than one pulsation mode, but this can be due to the noise level and the resolution in the amplitude spectrum.
A possible cyclic behavior of the period could be caused by a beat between two very closely-spaced frequencies, or by the presence of an orbiting object in a binary system.
Presently we do not have enough data to distinguish between the three possible solutions (a frequently changing period or a cyclic behavior due to either mode interactions or binarity). It seems certain that the previous period jump (Hintz et al. 1998) is real, and cannot be explained by a cyclic behavior.
The period- and amplitude changes observed in this star make it a highly interesting object. Further observations are crucial for understanding the observed changes. Our results indicate that such observations should not be restricted to short observing runs confined to one single site, but rather be distributed over the full observing season.
© European Southern Observatory (ESO) 2000
Online publication: February 9, 2000