Notes. In all the spectra, a binning of a minimum of 50 counts per bin has been used, with the only exception of the ASCA observation, for which the data were already reduced. A simplified identification code (ID) was assigned to each observation. Observations 2, 3, 4, and 5 are affected by high soft proton flaring background (e.g., De Luca & Molendi 2004; Marelli et al. 2017). Such high background, especially for Obs. 3, is responsible for the low number of counts for these observations, resulting in the high errors of the fit results of these observations. For this reason, we merged the spectra of Obs. 1, 2, and 3, Obs. 4 and 5, and Obs. 8 and 9. The MOS exposure times and counts are intended to be the sum of such quantities for each camera. ^(*)ASCA counts are computed in the 0.5−10 keV band.