Lithium Abundances of Stars in Open Clusters.
Abstract
Image-intensifier instrumentation was used at the coude focus of the Lick 120-inch reflector to obtain spectrograms of F to K main-sequence stars in the Hyades, Pleiades, and Praesepe clusters, as well as stars still contracting toward the main sequence in NGC 2264. The abundance of lithium was calculated from the measured equivalent widths of Li i X6707, a grid of model atmospheres, and an empirical correction for saturation effects. Lithium is present in NGC 2264 in about the same amount as in F and early-G cluster main-sequence stars. No Li abundances are observed to exceed the present interstellar upper limit. Because of possible differences in initial Li content among clusters, it is difficult to separate the effects of depletion during pre-main-sequence evolution from later slow destruction on the main sequence. However, the Pleiades G and K stars appear to be genuinely overabundant in Li with respect to the Hyades and imply a mainsequence depletion timescale of 1.5 X 10' years for soiar-type stars, decreasing to about half this value for K0 V stars. If Pleiades abundances represent zero-age main-sequence values, a shift of about 0.12 in B - V is necessary to bring Bodenheimer's theoretical relation between pre-main-sequence depletion and color into agreement with the observations.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 1972
- DOI:
- 10.1086/151328
- Bibcode:
- 1972ApJ...172...57Z