2D representation of the phase-dependent observed and calculated cyclotron lines of RX J1007 in 1997. The best-fit calculated spectral flux (color) is compared with the observed fluxes (contour lines). The abscissa is frequency in units of 10¹⁴ Hz, the ordinate is phase and data and model are displayed twice. The image shows the second and third harmonic with an indication of the first harmonic at the lowest frequencies.