Lithium in Blanco 1: Implications for Stellar Mixing
Abstract
We obtain lithium abundances for G and K stars in Blanco 1, an open cluster with an age similar to or slightly younger than the Pleiades. We critically examine previous spectroscopic abundance analyses of Blanco 1 and conclude that, while there were flaws in earlier work, it is likely that Blanco 1 is close in overall metallicity to the older Hyades cluster and more metal-rich than the Pleiades. However, we find Blanco 1 has Li abundances and rotation rates similar to the Pleiades, contradicting predictions from standard stellar evolution models, in which convective pre-main-sequence (PMS) Li depletion should increase rapidly with metallicity. If the high metallicity of Blanco 1 is subsequently confirmed, our observations imply (1) that a currently unknown mechanism severely inhibits PMS Li depletion; (2) that additional nonstandard mixing modes, such as those driven by rotation and angular momentum loss, are then responsible for main-sequence Li depletion between the ages of Blanco 1 and the Hyades; and (3) that in clusters younger than the Hyades, metallicity plays only a minor role in determining the amount of Li depletion among G and K stars. These conclusions suggest that Li abundance remains a useful age indicator among young (<700 Myr) stars even when metallicities are unknown. If nonstandard mixing is effective in Population I stars, the primordial Li abundance could be significantly larger than present day Population II Li abundances because of prior Li depletion.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 1999
- DOI:
- 10.1086/306684
- arXiv:
- arXiv:astro-ph/9809106
- Bibcode:
- 1999ApJ...511..218J
- Keywords:
-
- GALAXY: OPEN CLUSTERS AND ASSOCIATIONS: INDIVIDUAL: NAME: BLANCO 1;
- STARS: ABUNDANCES;
- STARS: INTERIORS;
- STARS: LATE-TYPE;
- Galaxy: Open Clusters and Associations: Individual: Name: Blanco 1;
- Stars: Abundances;
- stars: interiors;
- stars: late-type;
- Astrophysics
- E-Print:
- 18 pages, 3 figs. To appear in ApJ Vol. 511 (Jan 20 1999)