# The variability of X-ray/UV ratio in active galactic nuclei.

Chiaraluce E. , Vagnetti F., Tombesi F., Paolino M.

Comunicazione
III - Astrofisica
Aula 32B-1 - Giovedì 20 h 11:00 - 13:00
The relation between X-ray/UV ratio and UV luminosity in Active Galactic Nuclei is affected by a relatively large dispersion. Nevertheless, it has been used to build a Hubble diagram for Quasars. We estimated, through an ensemble variability study via Structure Function, that variability in the X-ray/UV ratio contribute for $\sim 60$% to the variance of the relation. We found that the remaining dispersion cannot be explained by invoking black-hole mass and/or Eddington ratio. We found, for a small number of objects, a correlation of $\alpha_{OX}$ with the inclination angle, which may represent the starting point for future work.