Rotational Velocities of Low-Mass Stars in the Pleiades and Hyades

Abstract

The authors have used high-resolution echelle spectra to estimate rotational velocities for K and M dwarfs in the Hyades. All of the K dwarfs have rotational velocities less than the instrumental limit of 10 km s-1. Most of the M dwarfs with (R-I)K > 1.0 have detectable rotational velocities, with 10 < v sin i < 20 km s-1. Combining these data with results from the younger Pleiades and α Persei clusters, the authors find that G dwarfs spin down from ≡100 km s-1 to ≡10 km s-1 in less than 4×107yr, whereas M dwarfs take an order of magnitude longer to spin down.