The Gaia-ESO Survey: A new diagnostic for accretion and outflow activity in the young cluster NGC 2264

R. Bonito, L Prisinzano, L Venuti, F. Damiani, Giusi Micela, G. Sacco, G Traven, K. Biazzo, L Sbordone, T Masseron, T. Zwitter, A. Gonneau, A Bayo, V. Roccatagliata, S. Randich, J. S. Vink, P Jofre, E. Flaccomio, L. Magrini, G CarraroL. Morbidelli, A. Frasca, L. Monaco, E Rigliaco, C Worley, A. Hourihane, G Gilmore, E. Franciosini, J. Lewis, Sergey Koposov