In this work , which is a continuation of \citet Castello2016 , we present new X-ray and infrared ( IR ) data for a sample of active galactic nuclei ( AGN ) covering a wide range in Eddington ratio over a small luminosity range .
In particular , we rigorously explore the dependence of the optical-to-X-ray spectral index \alpha _ { OX } and the IR-to-optical spectral index on the dimensionless accretion rate , \dot { \mathcal { M } } = \dot { m } / \eta where \dot { m } = L _ { AGN } / L _ { Edd } and \eta is the mass-to-radiation conversion efficiency , in low and high accretion rate sources .
We find that the SED of the faster accreting sources are surprisingly similar to those from the comparison sample of sources with lower accretion rate .
In particular : i ) the optical-to-UV AGN SED of slow and fast accreting AGN can be fitted with thin AD models . ii ) The value of \alpha _ { OX } is very similar in slow and fast accreting systems up to a dimensionless accretion rate \dot { \mathcal { M } } _ { c } \sim 10 .
We only find a correlation between \alpha _ { OX } and \dot { \mathcal { M } } for sources with \dot { \mathcal { M } } > \dot { \mathcal { M } } _ { c } .
In such cases , the faster accreting sources appear to have systematically larger \alpha _ { OX } values . iii ) We also find that the torus in the faster accreting systems seems to be less efficient in reprocessing the primary AGN radiation having lower IR-to-optical spectral slopes . These findings , failing to recover the predicted differences between the SEDs of slim and thin ADs within the observed spectral window , suggest that additional physical processes or very special geometry act to reduce the extreme UV radiation in fast accreting AGN .
This may be related to photon trapping , strong winds , and perhaps other yet unknown physical processes .