Letter to the Editor

Signature of non-isotropic distribution of stellar rotation inclination angles in the Praesepe cluster^★

Konkoly Observatory of the Hungarian Academy of Sciences, Konkoly Thege ut. 13–15, 1121 Budapest, Hungary
e-mail: kovacs@konkoly.hu

Received: 12 June 2017
Accepted: 6 March 2018

Abstract

The distribution of the stellar rotation axes of 113 main sequence stars in the open cluster Praesepe are examined by using current photometric rotation periods, spectroscopic rotation velocities, and estimated stellar radii. Three different samples of stellar rotation data on spotted stars from the Galactic field and two independent samples of planetary hosts are used as control samples to support the consistency of the analysis. Considering the high completeness of the Praesepe sample and the behavior of the control samples, we find that the main sequence F − K stars in this cluster are susceptible to rotational axis alignment. Using a cone model, the most likely inclination angle is 76^° ± 14^° with a half opening angle of 47^° ± 24^°. Non-isotropic distribution of the inclination angles is preferred over the isotropic distribution, except if the rotation velocities used in this work are systematically overestimated. We found no indication of this being the case on the basis of the currently available data.