Emergence of a lithium dip in ~35 Myr "Snake" Open Clusters
Abstract
We report the discovery of a lithium dip (Li-dip) in the stellar "Snake" (age = 35 5 Myr), challenging the classical view that Li-dips emerge only at ages 150 Myr. Using high-resolution spectra from GALAH DR4 (R 28,000) for 211 member stars, we identify a clear depletion feature in a Teff range of 6200--6800 K with a depth of A(Li) ≈ 0.40 dex. Our analysis reveals two key advances: the Li-dip appears 100 Myr earlier than the previous observations, and within the dip temperature range, a significant correlation is found between rotational velocity and lithium depletion. Specifically, fast rotators (v i > 25 km s-1) exhibit stronger lithium depletion than slow rotators (v i < 25 km s-1). This trend suggests that faster rotators develop stronger rotational shear at the convective-radiative boundary, which enhances turbulent mixing and accelerates lithium destruction. It is also found that the lower temperature edge of the lithium plateau can reach as low as 5500 K for the young open clusters.