The variability of delta Ceti.
Abstract
Differential uvby observations of the well-known β Cephei star δ Cet, obtained on seven nights in 1981 and on one night in 1982, are presented and analysed. Contrary to a recent report, no variation in the shape of the light curves is found. However, a marginal night-to-night variation of the 1981 amplitudes is noted. It is then demonstrated that the amplitude variation was caused either by a secondary short-period component with an amplitude not exceeding 0m.0016, or by slow drifts in the differential magnitudes. In addition, it is shown that all available epochs of maximum light, except three unreliable ones, can be accounted for by a parabolic ephemeris which implies an increase of the period at a rate of 0.47 ± 0.09 sec/century. However, it is also shown that the epochs of maximum light from 1963 onwards can be satisfactorily represented with a constant period, equal to 0d.16113762 ± 0d.00000002. The available epochs of maximum radial-velocity are then examined. No compelling evidence for a variation of the phase lag between the light and radial-velocity curves is found. From modern radial-velocity data, a phase lag equal to 0.200 ± 0.005 is derived. Finally, it is shown that the available photometric observations are still not sufficient to detect a secular light amplitude change.
- Publication:
-
Astronomy and Astrophysics Supplement Series
- Pub Date:
- March 1988
- Bibcode:
- 1988A&AS...72..449J