A large sample of photometric rotation periods for FGK Pleiades stars

Abstract

Using data from the Hungarian-made Automated Telescope Network (HATNet) survey for transiting exoplanets, we measure photometric rotation periods for 368 Pleiades stars with 0.4 ≲ M ≲ 1.3 M ⊙ . We detect periodic variability for 74 per cent of the cluster members in this mass range that are within our field-of-view, and 93 per cent of the members with 0.7 ≲ M ≲ 1.0 M ⊙ . This increases, by a factor of 5, the number of Pleiades members with measured periods. We compare these data to the rich sample of spectroscopically determined projected equatorial rotation velocities (v sin i) available in the literature for this cluster. Included in our sample are 14 newly identified probable cluster members which have proper motions, photometry and rotation periods consistent with membership. For stars with M ≳ 0.85 M ⊙ the rotation periods, v sin i and radius estimates are consistent with the stars having an isotropic distribution of rotation axes, if a moderate differential rotation law is assumed. For stars with M ≲ 0.85 M ⊙ , the inferred sin i values are systematically larger than 1.0. These observations imply that the combination of measured parameters P(v sin i)/R is too large by ∼24 per cent for low-mass stars in this cluster. By comparing our new mass-period relation for the Pleiades to the slightly older cluster M35, we confirm previous indications that the spin-down stalls at ∼100 Myr for the slowest rotating stars with 0.7 ≲ M ≲ 1.1 M ⊙ ― a fact which may indicate that the internal transport of angular momentum is inefficient in slowly rotating solar-mass stars.