Broad-band short term X-ray spectral variability of the quasar PDS 456
Abstract
We present an analysis of a recent 500 ks Suzaku observation, carried out in 2013, of the nearby (z=0.184) luminous (L_{bol}∼10^{47} erg s^{-1}) quasar PDS 456 in which the X-ray flux was unusually low. Short term X-ray spectral variability has been detected, which may be caused by two variable coverers of column density log (N_{H,1}/cm^{-2})=22.3±0.1 and log (N_{H,2}/cm(-2) )=23.2±0.1 We find that the partial covering requires an outflow velocity of ∼0.25 c, coincident with the velocity of the highly ionised outflow at the 99.9 % confidence level. Therefore the partial covering clouds could be the denser clumpy part of an inhomogeneous wind. An obscuration event occurs 1250 ks into the observation, where the spectrum becomes totally opaque at Fe K. This implies that the size of the absorber and likewise the X-ray emitter, to be less than 20 Rg. We also analyse the flaring behaviour in the lightcurve. The behaviour of the soft and hard X-ray flux, suggested a corona characterised by an extended "warm" region of ∼20 Rg in size combined with more compact regions of "hot" electrons of ∼8 Rg in size.
- Publication:
-
The Extremes of Black Hole Accretion
- Pub Date:
- July 2015
- Bibcode:
- 2015ebha.confE..48M