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The correlation between the X-ray and UV luminosities observed in quasars,spanning a wide redshift range and holding true for several decades in bothspectral bands, suggests the presence of a universal mechanism governing thetransfer of energy from the accretion disc to the hot corona. In this study, weleverage X-ray spectroscopic data extracted from the Chandra Source Catalog 2.0for a sample of over $2000$ quasars from the Sloan Digital Sky Survey DataRelease 14 (SDSS DR14). Our analysis reveals a reduced intrinsic dispersion inthe $L_{\rm{X}}-L_{\rm{UV}}$ relation at higher redshifts ($\delta < 0.2$ dex)compared to previous studies relying on photometric data from catalogs.Additionally, our findings confirm the stability of this relation up toredshifts of approximately $4.5$. The $L_{\rm{X}}-L_{\rm{UV}}$ relation canalso serve as a tool to investigate the physics of accretion by identifyingoutliers - sources that exhibit a different state of the accretion disc-hotcorona system compared to the average population. For instance, X-ray-weakquasars are sources with reduced X-ray emissions due to a radiativelyinefficient state of the corona, and their optical properties suggest thepresence of a powerful accretion disc wind. The wealth of spectroscopic dataavailable in the CSC 2.0-SDSS catalogs opens up the opportunity for a morecomprehensive exploration of the central engine in AGN.

The relation between X-ray and UV emission in quasars