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 ct/ks. In this paper we present results for the quasar from a 65 ks XMMNewton observation, which well constrains its spectral shape. The quasar is clearly detected with a total of ∼ 460 net counts in the 0.2-10 keV band. The spectrum is characterised by a simple power-law model with photon index of T = 2.30+0.10-0.10, and the intrinsic 2-10 keV luminosity is 3.14×1045erg s-1. The 1 σ upper limit to any intrinsic absorption column density is NH= 6.07 × 1022cm-2. No significant iron emission lines were detected. We derive the X-ray-to-optical flux ratio αoxof -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.
|Original language||English (US)|
|State||Published - May 17 2017|
- Galaxies: Active
- Galaxies: High-redshift
- Quasar: Individual: SDSS J010013.02+280225.8
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