Speaker
Description
Lithium (Li), a big-bang product that is sensitive to temperature in stellar interiors, is found to be enriched in 1$\%$ of giants in Milky Way and dwarf-spheroidals which pose challenges in low mass star's evolution. A systematic search for Li-strong stars using LAMOST spectra doubled the existing catalog of Li-rich stars, and spans super-solar metallicity to beyond [Fe/H]$\sim$-3 in different Galactic populations. Abundance analysis of selected candidates in disk and halo, using Subaru HDS spectra, confirmed Li-richness. The sample on HR-diagram occupied from subgiant branch to all along RGB, indicates multiple origins for Li anomaly. Existence of Li-rich subgiants suggest high Li in post-first-drege-up giants may preserved from its progenitor, however, internal Li production followed by extra-mixing and/or binary mergers are favorable for giants close to luminosity bump. Be abundances derived from Subaru near-UV spectra suggests no clear correlation with Li, putting constraints on pollution from planet-ingestion. Absence of anomaly in other elements put constraints on pollution from binary companions. We will discuss possible Li origins for our sample and focus on whether any common mechanism that could explain Li enrichment in giants spanning large metallicity range, which provide constraints on Li contribution from metal-poor giants toward Galactic Li enrichment.
Affiliation
NATIONAL ASTRONOMICAL OBSERVATORIES, CHINESE ACADEMY OF SCIENCES (NAOC)
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