Dynamical spectra for the data acquired in 2012. Observed Narval 2012 overplotted line profiles (bottom panels) of Hα (left), Hβ (middle), and Hγ (right), and dynamical spectra of differences between the individual hydrogen line profiles and the profile with the lowest core emission highlighted by the red colour. The phases are based on the period determined in Sect. 3, P_rot = 51.7 d.