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

TL;DR

This study reports the discovery of HD 77361, a super Li-rich K giant with an unusually low 12C/13C ratio, challenging existing theories of stellar mixing and lithium enrichment.

Contribution

It presents detailed spectroscopic analysis of HD 77361, identifying it as a unique case among low luminosity, low mass K giants with high lithium and low 12C/13C ratio, expanding understanding of stellar evolution.

Findings

HD 77361 is a super Li-rich K giant with log ε(Li) = 3.82.

It has a very low 12C/13C ratio of 4.3.

It is the only low luminosity, low mass super Li-rich K giant with such a low 12C/13C ratio.

Abstract

Results from high resolution spectroscopic analysis of HD 77361 are reported. The LTE analysis shows that HD 77361 is a K giant of atmospheric parameters: Teff = 4580 +/- 75 K, log$g$ = 2.5 +/- 0.1, and \xi_{t} = 1.40 +/-0.5 km/s. We found that the atmosphere of HD 77361 is highly enriched in Li with log \epsilon (Li) = 3.82 +/- 0.1. With this finding the total number of super Li-rich K giants (log \epsilon(Li) >= 3.3 ISM value) known till 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 RGB luminosity bump phase, HD 77361 shows 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_sun = 1.66 +/- 0.1) low mass K giant (M = 1.5 +/- 0.2M_sun) 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.