HD 77361: A new case of super Li-rich K giant with anomalous low 12C/13C ratio

Abstract

Results from high-resolution spectroscopic analysis of HD 77361 are reported. LTE analysis shows that HD 77361 is a K giant of atmospheric parameters: T eff = 4580 ± 75 K, log g = 2.5 ± 0.1, and ξt = 1.40 ± 0.5 km s-1. We found that the atmosphere of HD 77361 is highly enriched in Li with log ε (Li) = 3.82± 0.1. With this finding the total number of super Li-rich K giants (log ε(Li) ≥ 3.3 ISM value) known to date reached six. Contrary to first dredge-up, extra-deep mixing and the associated cool bottom processing, and other recent predictions for K giants on the red giant branch (RGB) luminosity bump phase, HD 77361 shows a very low value of 12C/13C = 4.3± 0.5, having, simultaneously, very large amount of Li. Also, HD 77361 is the only Population I low-luminosity (log L/L ⊙ = 1.66 0.1) low-mass K giant (M = 1.5 ±0.2 M ⊙) among the known super Li-rich K giants that has a very low 12C/13C ratio. Results of HD 77361 further constrain our theoretical understanding of Li enhancement in the atmospheres of RGB stars. © 2009. The American Astronomical Society.