Abstract Details
| Name: raghubar singh Affiliation: IIA, Bengaluru Conference ID: ASI2019_477 Title : Spectroscopic and asteroseismic study of Li-rich giants Authors and Co-Authors : Raghubar Singh, B. Eswar Reddy, Bharat Kumar Yerra Abstract Type : Oral Abstract Category : Stars, ISM and Galaxy Abstract : Lithium is a light and fragile element which got synthesized during Big Bang nucleosynthesis together with deuterium and He. Due to the low dissociation energy of Li, it gets destroyed above 2.5 million Kelvin which is much lower than stellar core temperature. Post main sequence star faces first dredge up (FDU) and as a result, the chemical abundance of different elements gets changed in the surface. The elements synthesized during the main sequence appear on the surface of the red giant. The abundance of N, 13C, 3He increases and abundance of Li reduces post-FDU. During further evolution along the red giant branch an extra mixing has been hypothesized which is well-established observationally. It is expected theoretically that Li should be low in RGB branch post-FDU. There are a small fraction of red giants having Li abundance higher than ISM value. This is puzzling since the discovery of first Li-rich evolved star HD112127 by Wallerstein and Sneden in 1982. There are the different hypothesis to explain this event but exact explanation of this phenomena always hampered by lack of precise evolutionary state determination. But now we are having multiple ways of determining evolutionary state of the star based on HR diagram, Asteroseismology and spectroscopically determined CN abundances. We have selected a sample of the evolved star from GAIA dr2 catalog. Which gives a huge number of the star. Final sample contains a magnitude-limited collection of stars with available low-resolution spectra. There is a small group of these stars which overlaps in the Kepler field for which evolutionary state based on asteroseismology is known. We found that these evolved low mass stars are core He-burning stars. In this talk, I would like to explain our recent results based on the spectroscopic study of these stars and asteroseismic study from literature. |