A Self-Consistent Test of Comptonisation Models Using Bepposax Observations of Seyfert Galaxies

We test accurate models of Comptonisation spectra over BeppoSAX observations of Seyfert galaxies focusing on the long look at NGC 5548. The hot plasma temperature derived with these models is significantly higher than that obtained fitting the same data with a power law plus high energy cut off model for the continuum. This is due to the fact that in anisotropic geometries Comptonisation spectra show "intrinsic" curvature which moves the fitted high energy cut-off to higher energies. We also show preliminary results of our analysis of a sample of 5 other Seyfert galaxies.