On the photometric behaviour of the Pleiades K dwarf HII 1883

Department of Physics and Astronomy, The University, Glasgow G12 8QQ, Scotland, UK

Received: 11 September 2003
Accepted: 17 March 2004

Abstract

Photometric data from a variety of sources have been analysed to check if effects of differential rotation or evolutionary spin-down can be detected in HII 1883. Although the same light-curve form may be maintained for several years, shape changes and phase shifts do not allow sufficiently long time-bases for the required accuracy of period determination. One form of light-curve may have a tendency to recur with phase coherence. Using this observation allows determination of three potentially more accurate periods relative to the one previously established, but the choice of any revised value is subject to imprecise knowledge of the integer number of cycles over the time-base. The phase-locked tendency, if confirmed, requires some mechanism for spots to recur at a given longitude. A suggestion of the star being a magnetic oblique rotator is mooted but other observational and theoretical support would be required to promote this notion further. Evidence of small short-term changes occurring over just a few periods is explored. Comparison of the contemporaneous light-curve with the Hα line emission RV variations reveals a phase difference of , so making a connection that the disturbances producing the photometric signals have the same location as those generating at least some part of the Hα emission. Finally a multi-spot model is presented to mimic the observed light-curves.