Variability of the High-velocity Outflow in the Quasar PDS 456

Reeves, J.N.; Braito, V.; Gofford, J.; Sim, S.A.; Behar, E.; Costa, M.; Kaspi, S.; Matzeu, G.; Miller, L.; O'Brien, P.; Turner, T.J.; Ward, M.

Abstract

We present a comparison of two Suzaku X-ray observations of the nearby (z = 0.184), luminous (L bol ~ 1047 erg s–1) type I quasar, PDS 456. A new 125 ks Suzaku observation in 2011 caught the quasar during a period of low X-ray flux and with a hard X-ray spectrum, in contrast with a previous 190 ks Suzaku observation in 2007 when the quasar appeared brighter and had a steep (Γ > 2) X-ray spectrum. The 2011 X-ray spectrum contains a pronounced trough near 9 keV in the quasar rest frame, which can be modeled with blueshifted iron K-shell absorption, most likely from the He- and H-like transitions of iron. The absorption trough is observed at a similar rest-frame energy as in the earlier 2007 observation, which appears to confirm the existence of a persistent high-velocity wind in PDS 456, at an outflow velocity of 0.25-0.30c. The spectral variability between 2007 and 2011 can be accounted for by variations in a partial covering absorber, increasing in covering fraction from the brighter 2007 observation to the hard and faint 2011 observation. Overall, the low-flux 2011 observation can be explained if PDS 456 is observed at relatively low inclination angles through a Compton-thick wind, originating from the accretion disk, which significantly attenuates the X-ray flux from the quasar.

Citation

Reeves, J., Braito, V., Gofford, J., Sim, S., Behar, E., Costa, M., …Ward, M. (2014). Variability of the High-velocity Outflow in the Quasar PDS 456. Astrophysical Journal, 780(1), Article 45. https://doi.org/10.1088/0004-637x/780/1/45

• Journal Article Type: Article
• Publication Date: Jan 1, 2014
• Deposit Date: May 29, 2014
• Publicly Available Date: Jun 23, 2014
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 780
• Issue: 1
• Article Number: 45
• DOI: https://doi.org/10.1088/0004-637x/780/1/45
• Keywords: Black hole physics, Quasars: individual (PDS 456), X-rays: galaxies.
• Public URL: https://durham-repository.worktribe.com/output/1430642