SIMBAD references

In recent years the short-time X-ray variability of AGNs has been interpreted in terms of varying absorption from the temporary occultation of the primary X-ray source itself owing to the passage of absorbing clouds. Detailed analyses have shown that these clouds are located in the same region and have physical properties similar to those of broad line region (BLR) emitting clouds. The aim of this paper is to investigate in detail whether the same group of orbiting clouds can account for BLR emitting cloud properties and X-ray eclipsing cloud properties as well. To this purpose we looked for a distribution in size for the cloud number density capable of fulfilling the observational requirements of the two groups. The existence of such a distribution not only proves that BLR clouds and eclipsing clouds can be part of the same "family", but also allows us to estimate the total mass content in clouds orbiting around an AGN black hole.