  Estimating the black hole mass at the center of galaxies is a fundamental
step not only for understanding the physics of accretion, but also for the
cosmological evolution of galaxies. Recently a new method, based solely on
X-ray data, was successfully applied to determine the black hole mass in
Galactic systems. Since X-rays are thought to be produced via Comptonization
process both in stellar and supermassive black holes, in principle, the same
method may be applied to estimate the mass in supermassive black holes. In this
work we test this hypothesis by performing a systematic analysis of a sample of
AGNs, whose black hole mass has been already determined via reverberation
mapping and which possess high quality XMM-Newton archival data. The good
agreement obtained between the black hole masses derived with this novel
scaling technique and the reverberation mapping values suggests that this
method is robust and works equally well on stellar and supermassive black
holes, making it a truly scale-independent technique for black hole
determination.
