The Chandra X-ray Observatory Spectrum of the z=5.99 Quasar SDSSJ1306+0356

We report on the 120 ks ACIS-S Chandra observation of the z=5.99 quasar SDSSJ130608.26+035626.3. This radio-quiet AGN was clearly detected in the X-ray band (up to a rest-frame energy of ∼35 keV). We detect 121 photons, with about 3 photons due to background, giving an unabsorbed flux in the observed 0.5-5.0 keV band of 6.3 × 10^-15 {erg/cm^2/s}. No temporal variability was detected either during the observation or in the 2 years since an earlier Chandra "snapshot" observation. We present the observed 0.5-5.0 keV spectrum (3.5-35.0 keV in the rest-frame) which indicates the presence of a redshifted Fe-K emission line (at ∼ 2σ confidence). The Chandra X-ray spectrum of this distant AGN gives a photon index of 1.8 ± 0.2 and an X-ray-to-optical flux ratio index, α_ox, of 1.62 which is similar to those of lower redshift radio-quiet quasars. The implications of this observation for AGN evolution as a function of redshift are briefly discussed. This work was supported in part by NASA contract NAS8-39073 to the Chandra X-ray Center and CXC grant G03-4120X to SAO.