Long Term X-ray Spectral Variability of PDS 456 with Suzaku, XMM-Newton and NuSTAR
Abstract
We present the recent Suzaku and simultaneous XMM/NuSTAR observations of PDS 456 (z=0.184) taken in 2013 each with a 500ks exposure. PDS 456 is an object which shows strong X-ray spectral variability, varying from bright/soft (with Γ>2) to low/hard (with Γ<1). The 2013 Suzaku observations catches PDS 456 in a low flux (2.1×10^{-12}ergs cm^{-2} s^{-1}) with a hard X-ray spectrum. In contrast, the XMM/NuSTAR observations in August/Sept 2013 were at a much was a higher flux (7.0×10^{-12}ergs cm^{-2} s^{-1}), with an overall soft X-ray spectrum. When compared to prevous observations, PDS 456 seems to vary in two distinctive ways. In the low flux Suzaku observations, most of the spectral changes are due to a variable X-ray absorber, with a high covering fraction for the absorber. In contrast the XMM/NuSTAR observations, which were brighter and less absorbed, appear to require intrinsic continuum changes to the hard X-ray powerlaw account for the spectral variations. We also discuss whether changes in an innermost accretion disk reflector could account for the spectral variability instead of a partial covering absorber.
- Publication:
-
The X-ray Universe 2014
- Pub Date:
- July 2014
- Bibcode:
- 2014xru..confE.239C