Top of each panel: observed, continuum-normalized FIES spectra of CoRoT 102899501 (solid line) acquired on 2010 October 10 (upper panels) and 2010 November 1 (lower panels) in the Hβ (left panels) and Hα (right panels) regions. The spectrum template of the non-active star is represented in dotted lines. Bottom of each panel: difference between observed and template spectra. The residual Hα profile is shifted downwards for the sake of clarity. The hatched areas represent the excess emissions that have been integrated to obtain the net line EW.