Determination of the coronal properties of luminous quasars at cosmological redshifts
Abstract
Several precise measurements of high-energy cutoffs in the X-ray spectra of bright local AGN have been reported recently. These measurements can be also done for luminous quasars at cosmological redshifts. The shift of the high-energy cutoff to lower energies, in the observer frame, compensates for the relative faintness of the source, allowing an estimate of the coronal temperature analogous to the ones done for local, low luminosity but very bright AGN. We present the analysis of the joint XMM-Newton and NuSTAR observations of the luminous radio-quiet quasar QSO B2202-209 (z=0.53; L(2-10 keV)= 1.93× 10^{45} erg/s). Assuming a Comptonization model, we estimated a coronal temperature of kT_{e} = (42± 3) keV and KT_{e}=(56 ± 3) keV for a spherical and a slab geometry, respectively, for B2202-209. The unusual X-ray loudness of this quasar (α_{OX} = 1.00 ± 0.02) and the exceptionally strong optical [O III] line, that we found, can be explained by a nearly edge-on disc, leading to a reduction in the observed ultraviolet continuum light.
- Publication:
-
The X-ray Universe 2017
- Pub Date:
- October 2017
- Bibcode:
- 2017xru..conf..109K