The lithium-rotation correlation for WTTS in Taurus-Auriga

Abstract

Surface lithium abundance and rotation velocity can serve as powerful and mutually complementary diagnostics of interior structure of stars. So far, the processes responsible for the lithium depletion during pre-main sequence evolution are still poorly understood. We investigate whether a correlation exists between equivalent widths of Li (EW(Li)) and rotation period (P$_{rot}$) for Weak-line T Tauri stars (WTTSs). We find that rapidly rotating stars have lower EW(Li) and the fast burning of Li begins at the phase when star's P$_{rot}$ evolves towards 3 days among 0.9M$_\odot$ to 1.4M$_\odot$ WTTSs in Taurus-Auriga. Our results support the conclusion by Piau & Turch-Chiéze about a model for lithium depletion with age of the star and by Bouvier et al. in relation to rotation evolution. The turn over of the curve for the correlation between EW(Li) and P$_{rot}$ is at the phase of Zero-Age Main Sequence (ZAMS). The EW(Li) decreases with decreasing P$_{rot}$ before the star reaches the ZAMS, while it decreases with increasing P$_{rot}$ (decreasing rotation velocity) for young low-mass main sequence stars. This result could be explained as an age effect of Li depletion and the rapid rotation does not inhibit Li destruction among low mass PMS stars.