Lithium and rotation in the Hyades F dwarfs

Data on Li/H abundances have been assembled for 32 Hyades F dwarfs from high signal-to-noise, high-spectral-resolution observations from the coude spectrographs at the CFH and Hale telescopes. The middle F stars show a regular pattern in the Li-temperature profile, in particular a narrow and well-defined region with large Li deficiencies as first reported by Boesgaard and Tripicco (1986). This Li-temperature profile is compared with the rotation-temperature profile based on v sin i data from Kraft. A relationship between the Li abundance and v sin i may be present for the stars in the Li dip. It is possible that the decreasing stellar rotation (with decreasing surface temperature and stellar mass) helps to slow down the circulation of Li atoms to depths where they would be destroyed by nuclear reactions. The rise in Li/H on the cool side of the Li dip may result in part from the slower rotation, in spite of the deepening of the convection zone. The minimum of the Li abundances occurs at T of about 6650 K, which coincides with both the sharp decrease in rotation and the transition in stellar activity from high activity to activity controlled by the stellar dynamo.