MEASURING CORONAL PROPERTIES OF TWO HIGH REDSHIFT comma LUMINOUS QUASARS

We propose NuSTAR and XMM joint observations of two quasars at z2.36 andz3.37, with the main goal of measuring the highenergy cutoffs of their Xrayemission. Only recently the high S/N NuSTAR spectra allowed precise measurementsof these parameters for the brightest local AGN, finding cutoff energies above100virgulkeV. Here we demonstrate that the same estimates are possible also for thebrightest highz quasars, if (and only if) the whole 0.580virgulkeV band isobserved. The scientific outcome is of great value: we will be able to testwhether the same physical conditions hold in quasars at luminosities > 100times higher than those probed so far in the nearby Universe. An importantadditional scientific goal will be the study of the Xray absorption by the intervening IGM. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]