Revealing the location and structure of the accretion disk-wind in PDS456

Journal article

We present evidence for the rapid variability of the high velocity iron K-shell absorption in the nearby ($z=0.184$) quasar PDS456. From a recent long Suzaku observation in 2013 ($\sim1$Ms effective duration) we find that the the equivalent width of iron K absorption increases by a factor of $\sim5$ during the observation, increasing from $<105$eV within the first 100ks of the observation, towards a maximum depth of $\sim500$eV near the end. The implied outflow velocity of $\sim0.25$c is consistent with that claimed from earlier (2007, 2011) Suzaku observations. The absorption varies on time-scales as short as $\sim1$ week. We show that this variability can be equally well attributed to either (i) an increase in column density, plausibly associated with a clumpy time-variable outflow, or (ii) the decreasing ionization of a smooth homogeneous outflow which is in photo-ionization equilibrium with the local photon field. The variability allows a direct measure of absorber location, which is constrained to within $r=200-3500$$\rm{r_{g}}$ of the black hole. Even in the most conservative case the kinetic power of the outflow is $\gtrsim6\%$ of the Eddington luminosity, with a mass outflow rate in excess of $\sim40\%$ of the Eddington accretion rate. The wind momentum rate is directly equivalent to the Eddington momentum rate which suggests that the flow may have been accelerated by continuum-scattering during an episode of Eddington-limited accretion.

Authors: Gofford, J; Reeves, J; Braito, V; Nardini, E; Costa, M

• Publication status: Published
• Publisher: Institute of Physics Publishing
• Journal: ASTROPHYSICAL JOURNAL
• Volume: 784
• Issue: 1
• Pages: 77-77
• Publication date: 2014-02-15
• DOI: 10.1088/0004-637X/784/1/77
• EISSN: 1538-4357
• ISSN: 0004-637X
• Language: English
• Keywords: astro-ph.HE; astro-ph.CO