Example of a spectral fit in one of the 50 phase bins we used for the phase-resolved spectroscopy. This is one of the bins located inside the bars of the V-shaped feature. Upper panel: results of the best fit for the const*cyclabs*gabs*TBabs*(pegpwrlw + bbodyrad) model (best-fit model for the phase-averaged spectrum plus a cyclotron absorption line) to the EPIC PN spectrum. The blackbody (blue line) and power-law (green line) components are plotted. Lower panels: residuals (in standard deviation units) for the best fit obtained without (χ² = 539.2 for 347 d.o.f., null hypothesis probability ≃10⁻¹⁰), and with (χ² = 360.2 for 344 d.o.f., null hypothesis probability = 0.26) the cyclotron absorption line. The best-fit parameters for the cyclotron absorption line are E = 1.0 keV and width W = 4.0 keV. A factor 5 graphic rebin is used.