Evidence for a radiatively driven disc-wind in PDS 456?

Abstract

We present a newly discovered correlation between the wind outflow velocity and the X-ray luminosity in the luminous ($L_{\mathrm{bol}}\sim 10^{47}\mathrm{erg}{\mathrm{s}}^{-1}$) nearby ($z=0.184$) quasar PDS\,456. All the contemporary XMM-Newton, NuSTAR and Suzaku observations from 2001--2014 were revisited and we find that the centroid energy of the blueshifted Fe\,K absorption profile increases with luminosity. This translates into a correlation between the wind outflow velocity and the hard X-ray luminosity (between 7--30\,keV) where we find that $v_{\mathrm{w}}/c\propto L_{7-30}^3$ where ${\hat{I}}^3=0.22\pm 0.04$. We also show that this is consistent with a wind that is predominately radiatively driven, possibly resulting from the high Eddington ratio of PDS\,456.

5 pages, 3 figures. Accepted for publication in MNRAS Letter