Membership and lithium of young clusters

The models are also compared with the observed lithium depletion patterns. To reproduce the colour-magnitude diagram and the observed lithium depletion pattern in Gamma Vel A and B and in 25 Ori one needs to assume both a reduced convection efficiency, with {alpha}_ML_=1.0, and an effective surface spot coverage of about 20%. We obtained ages of 18^+1.5^_-4.0_ Myr and 21^+3.5^_-3.0_ Myr for Gamma Vel A and B, respectively, and 19^+1.5^_-7.0_ Myr for 25 Ori.

However, a single isochrone is not sufficient to account for the lithium dispersion, and an increasing level of spot coverage as mass decreases seems to be required. On the other hand, the older clusters (NGC 2451B at 30^+3.0^_-5.0_Myr, NGC 2547 at 35^+4.0^_-4.0_Myr, and NGC 2516 at 138^+48^_-42_Myr) are consistent with standard models, with {alpha}_ML_=2.0 and no spots, except at low masses: a 20% spot coverage appears to better reproduce the sequence of M-type stars and might explain the observed spread in lithium abundances.

The quality of Gaia-ESO data combined with Gaia allows us to gain important insights on pre-main sequence evolution. Models including starspots can provide a consistent explanation of the cluster sequences and lithium abundances observed in young clusters, although a range of starspot coverage is required to fully reproduce the data.