ORIGIN OF LITHIUM ENRICHMENT IN K GIANTS
- Indian Institute of Astrophysics, Bengaluru 560034 (India)
- McDonald Observatory, University of Texas, Austin, TX 78712 (United States)
In this Letter, we report on a low-resolution spectroscopic survey for Li-rich K giants among 2000 low-mass (M {<=} 3 M{sub sun}) giants spanning the luminosity range from below to above the luminosity of the clump. Fifteen new Li-rich giants including four super Li-rich K giants (log {epsilon}(Li) {>=}3.2) were discovered. A significant finding is that there is a concentration of Li-rich K giants at the luminosity of the clump or red horizontal branch. This new finding is partly a consequence of the fact that our low-resolution survey is the first large survey to include giants well below and above the red giant branch (RGB) bump and clump locations in the H-R diagram. Origin of the lithium enrichment may be plausibly attributed to the conversion of {sup 3}He via {sup 7}Be to {sup 7}Li by the Cameron-Fowler mechanism but the location for the onset of the conversion is uncertain. Two possible opportunities to effect this conversion are discussed: the bump in the first ascent of the RGB and the He-core flash at the tip of the RGB. The finite luminosity spread of the Li-rich giants serves to reject the idea that Li enhancement is, in general, a consequence of a giant swallowing a large planet.
- OSTI ID:
- 21560433
- Journal Information:
- Astrophysical Journal Letters, Vol. 730, Issue 1; Other Information: DOI: 10.1088/2041-8205/730/1/L12; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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