Lithium in NGC 752

Abstract

Echelle spectra recorded at the Li I 6707 A line are reported for 19 main sequence members of NGC 752, an open cluster about 2.5 times older than the Hyades. A sharp decline of the lithium abundance toward cooler temperatures is found which is more pronounced than in the Hyades, as expected. The initial cluster lithium abundance is estimated at roughly 1 x 10 to the -9th. No significant increase of the lithium fraction in the gas of the Galactic disk apparently has occurred in at least the last 1.7 Gyr. Four stars in a very narrow temperature range centered near 6600 K show a deficiency of atmospheric lithium which ranges up to a factor of more than 30 compared to slightly hotter or cooler stars.