Simultaneous X-ray/optical/UV snapshots of active galactic nuclei from XMM-Newton: spectral energy distributions for the reverberation mapped sample

R. V. Vasudevan, A. C. Fabian

Published 2008-10-21Version 1

We employ contemporaneous optical, UV and X-ray observations from the XMM-Newton EPIC-pn and Optical Monitor (OM) archives to present, for the first time, simultaneous spectral energy distributions (SEDs) for the majority of the Peterson et al. (2004) reverberation mapped sample of active galactic nuclei (AGN). The raw data were reduced using the latest pipelines and are all analysed consistently. The virial mass estimates from Peterson et al. (2004) allow us to calculate Eddington ratios lambda_Edd for the sample using the bolometric accretion luminosities determined directly from the SEDs. We calculate hard X-ray bolometric corrections kappa_2-10keV for the sample and confirm a trend for increasing bolometric correction with Eddington ratio proposed in previous studies. Our comparison with previous work on these objects suggests that the OM bandpass may be less susceptible to intrinsic reddening than the far-UV peak of the thermal disc spectrum in AGN, yielding larger bolometric corrections than previous work: kappa_2-10keV ~ 15 - 30 for lambda_Edd <~ 0.1, kappa_2-10keV ~ 20 - 70 for 0.1 <~ lambda_Edd <~ 0.2 and kappa_2-10keV ~ 70 - 150 for lambda_Edd >~ 0.2, but part of this increase could be attributed to spectral complexity preventing accurate recovery of the intrinsic luminosity in some sources. Long-term optical-UV variability contributes a second-order, but significant change to the total bolometric luminosity when comparing multiple observations for individual objects.We also consider the effect of a recently proposed correction for radiation pressure when determining black hole masses with reverberation mapping, and find that the revised mass estimates do not significantly alter the range of bolometric corrections seen but may yield a narrower distribution of Eddington ratios.