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A new study led by astronomer from the Chinese Academy of Sciences has revealed evolutionary features of lithium for evolved stars, which is important for understanding the theory of stellar structure and evolution.
The results were published in a journal.
Different patterns for stars of different types can be seen in the abundances. Key information about internal stellar structure and evolution can be found in the signatures of Li.
The evolutionary features of Li from the red giant branch to the HeB stage have been hidden due to the difficulties of classification.
Thanks to the uncovered evolutionary stages and determined Li abundances, the researchers investigated the signatures of Li for stars evolving from the RGB to the HeB phase with the 1,848 giants selected in the LAMOST-Kepler/K.
There were no obvious crowd stars with high Li abundances near the bump that they found. There was no indication of Li depletion during the HeB phase.
The Li abundances of low-mass stars that just start their HeB phase showed an increase compared to the stars above. It was suggested that the helium flash might lead to moderate Li production.
The first author of the study said that a previous theoretical study had speculated that the amount of Li produced by helium flash could be limited.
The Li abundances of most low-mass ZAHeB stars are still lower than the lower limit of Li-rich stars in a classic definition, so the standard helium flash model cannot explain the high Li abundance in (super) Li-rich stars. Special mechanisms should be considered for Li-rich stars. Mergers are possible given that Li-rich stars can be found at any time during the steady-state phase of HeB.
The paper is timely and interesting, and is being rejuvenated by the existence of new, larger, more precise, and better characterized datasets, commented the reviewer of the paper.
The Astrophysical Journal Letters has more information on the Evolution of Giant Stars. There is a book titled "10847/2041-8213/ac224c".
The Astrophysical Journal Letters contains information.
The LAMOST-kepler data was retrieved from thephys.org on November 24, 2021.
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