Abstract: We study the link between the X-ray emission in radio-quiet active galactic nuclei (AGN) and the accretion rate on the central supermassive black hole using a statistically well-defined and representative sample of 71 type 1 AGN extracted from the XMM?Newton Bright Serendipitous Survey. We search and quantify the statistical correlations between some fundamental parameters that characterize the X-ray emission, i.e. the X-ray spectral slope, ?, and the X-ray ?loudness?, and the accretion rate, both absolute (?) and normalized to the Eddington luminosity (Eddington ratio, ?). We parametrize the X-ray loudness using three different quantities: the bolometric correction Kbol, the two-point spectral index ?OX and the disc/corona luminosity ratio. We find that the X-ray spectral index depends on the normalized accretion rate while the ?X-ray loudness? depends on both the normalized and the absolute accretion rate. The dependence on the Eddington ratio, in particular, is probably induced by the ? ? ? correlation. The two proxies usually adopted in the literature to quantify the X-ray loudness of an AGN, i.e. Kbol and ?OX, behave differently, with Kbol being more sensitive to the Eddington ratio and ?OX having a stronger dependence with the absolute accretion. The explanation of this result is likely related to the different sensitivity of the two parameters to the X-ray spectral index.

Authorship

Download reference