The seven sisters DANCe.II. Proper motions and the lithium-rotation-activity connection for G and K Pleiads

TL;DR

This study investigates the relationship between lithium depletion, rotation, and activity in G and K stars of the Pleiades cluster, confirming a strong link especially in certain luminosity ranges, and suggests activity may influence lithium observations.

Contribution

It provides a comprehensive analysis of the lithium-rotation-activity connection in Pleiades stars using extensive literature data and proper motion cross-matching, highlighting the role of activity and rotation in lithium abundance.

Findings

Strong link between activity, rotation, and lithium excess in certain stellar types.

Lithium overabundance may be partly due to observational effects from stellar activity.

Both activity and rotation influence the lithium problem in young stars.

Abstract

Stellar clusters are open windows to understand stellar evolution. Specifically, the change with time and the dependence on mass of different stellar properties. As such, they are our laboratories where different theories can be tested. We try to understand the origin of the connection between lithium depletion in F, G and K stars, rotation and activity, in particular in the Pleiades open cluster. We have collected all the relevant data in the literature, including information regarding rotation period, binarity and activity, and cross-matched with proper motions, multi-wavelength photometry and membership probability from the DANCe database. In order to avoid biases, only Pleiades single members with probabilities larger than p=0.75 have been included in the discussion. Results. The analysis confirms that there is a strong link between activity, rotation and the lithium equivalent width excess, specially for the range Lum(bol) = 0.5-0.2 Lsun (about K2-K7 spectral types or 0.75-0.95 Msun). It is not possible to disentangle these effects but we cannot exclude that the observed lithium overabundance is partially an observational effect due to enhanced activity, due to a large coverage by stellar spots induced by high rotation rates. Since a bona fide lithium enhancement is present in young, fast rotators, both activity and rotation should play a role in the lithium problem.