Scaling of the photon index Γ vs. the normalization N_BMC for M 87 (black line – target source) using extragalactic sources: ESO 243–49 HLX–1 and M 101 ULX–1 (reference sources). Black squares stand for RXTE data of ESO 243–49 HLX–1and blue triangles indicate M 101 ULX–1 data. The black dashed line indicates the Γ-Norm correlation corrected for a nucleus emission from M 87 using Chandra data (bright blue points). For the scaling of BH mass of M 87 we used this corrected Γ-normalization track.