Four unfolded spectra of Vela X-1 from XMM-Newton observation (2019) taken with EPIC-pn. Each spectrum is ∼283 s and corresponds to a different absorption column density value, from low N_H (light green) to high N_H (dark blue). The observation covers the 0.37−0.51 orbital phase range (Diez et al. 2023). The shaded zones cover the MAXI/GSC energy bands chosen for our analysis (2−4 keV and 4−10 keV).