Phase-dependent spectral variability for ObsID 304: each curve represents one of the best-fitting model from the eight phase-selected spectra. Models are normalized to unity at the reference energy of 10 keV. The blue and red curves correspond to spectra extracted in the phase intervals of the primary and secondary peak, respectively. The black spectrum shows a very shallow cyclotron line in the primary falling flank. The gray spectra correspond to the primary rising flank and secondary falling flank.