XMM-Newton observation of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.326

Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Date Issued
2017
Author(s)
Ai, Yanli
•
Fabian, A. C.
•
Fan, Xiaohui
•
Walker, S. A.
•
•
•
Dou, Liming
•
Wang, Feige
•
Wu, Xue-Bing
•
Feng, Longlong
DOI
10.1093/mnras/stx1231
Abstract
A brief Chandra observation of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.326 showed it to be a relatively bright, soft X-ray source with a count rate of about 1 count ks-1. In this article, we present results for the quasar from a 65-ks XMM-Newton observation, which constrains its spectral shape well. The quasar is clearly detected with a total of ∼460 net counts in the 0.2-10 keV band. The spectrum is characterized by a simple power-law model with a photon index of Γ = 2.30^{+0.10}_{-0.10} and the intrinsic 2-10 keV luminosity is 3.14 × 1045 erg s-1. The 1σ upper limit to any intrinsic absorption column density is NH = 6.07 × 1022 cm-2. No significant iron emission lines were detected. We derive an X-ray-to-optical flux ratio αox of -1.74 ± 0.01, consistent with the values found in other quasars of comparable ultraviolet luminosity. We did not detect significant flux variations either in the XMM-Newton exposure or between XMM-Newton and Chandra observations, which are separated by ∼8 months. The X-ray observation enables the bolometric luminosity to be calculated after modelling the spectral energy distribution: the accretion rate is found to be sub-Eddington.
Volume
470
Issue
2
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1587
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