Exploratory Chandra Observations of the Three Highest Redshift Quasars   Known
  We report on exploratory Chandra observations of the three highest redshift quasars known (z = 5.82, 5.99, and 6.28), all found in the Sloan Digital Sky Survey. These data, combined with a previous XMM-Newton observation of a z = 5.74 quasar, form a complete set of color-selected, z > 5.7 quasars. X-ray emission is detected from all of the quasars at levels that indicate that the X-ray to optical flux ratios of z ~ 6 optically selected quasars are similar to those of lower redshift quasars. The observations demonstrate that it will be feasible to obtain quality X-ray spectra of z ~ 6 quasars with current and future X-ray missions. 
W.N. Brandt, D.P. Schneider (PSU), X. Fan (IAS), M.A. Strauss, J.E.   Gunn (Princeton), G.T. Richards (PSU), S.F. Anderson (...