Speaker
Description
Standard stellar evolution predicts severe lithium depletion in evolved stars; however, a rare subset of giants with lithium abundances exceeding meteoritic values, known as “super Li-rich” (SLR; A(Li) > 3.3) stars, defies this expectation and presents a major astrophysical puzzle. To understand this extreme enhancement, it is essential to distinguish internal production (e.g., a “lithium flash”) and external pollution (e.g., binary mass transfer or planet engulfment) for possible origins. Because Li abundance alone cannot reveal its origin, a comprehensive and precise elemental abundance pattern is essential. In this presentation, we report on our program to derive precise stellar parameters and elemental abundances for four newly confirmed SLRs from the LAMOST MRS catalogue, followed up with high-resolution spectroscopic observations using Subaru/HDS and Gemini-N/MAROON-X, covering 400–900 nm. The Li abundances of these stars range from A(Li) ~ 3.6 to 4.5. Our targets include one subgiant, two red giants, and one supergiant, all exhibiting saturated Li 670.8 nm lines and spanning sub-solar to very metal-poor ranges. From the two observations with approximately one month separation, we detect indications of variability in spectral features of two targets, as seen in their H-alpha, Li 670.8 nm, and Na D line profiles. We aim to investigate the common or unique feature of these targets, exploring potential correlations with their evolutionary status or formation scenarios. Our results are compared to previously discovered SLRs and one ultra-Li-rich star (A(Li) ~ 6.5), for which an archive spectrum of Subaru/HDS is analyzed. Updated findings from this project will be presented in detail.
| Category | Observation |
|---|