091039

We propose a 80 ks ToO observation of a high-redshift openParz>=3closePar blazar during a gamma-ray flare detected by Fermi-LAT. So far comma only 12 high-redshift blazars have been detected in IquestionMark-rays. These objects are the most luminous and massive objects in the Universe comma which allow to study the formation of active galactic nuclei in the early Universe. Because the high-energy hump of their SED peaks in the MeV range comma X-ray and gamma-ray data is needed to constrain the hump s shape. We propose to get high-sensitivity comma simultaneous X-ray data during enhanced IquestionMark-ray activity of a blazar at high redshift. The data will be complemented by triggered radio observations. The resulting multiwavelength data set will yield important knowledge on the behaviour of flaring MeV blazars for future MeV telescopes.