PKS 0537-286, the high redshift FSRQ, giving new insights into the jet physics

We have performed a multiwavelength campaign on the high red-shift FSRQ PKS 0537-286 during October - November 2006 and February 2008. The automatic optical and near-infrared telescope (REM) and the Gamma-Ray Burst Optical and Near Infrared Detector (GROND) observed the source simultaneously to X-ray and hard X-ray satellite pointings with INTEGRAL/ISGRI, Swift/XRT and RXTE that allowed covering a wide range of energies. At X-ray energies no significant variability was found. The Swift/BAT light curve over two years of survey showed a constant flux level. We find a rather flat high energy spectrum and absorption at soft X-rays in excess to the Galactic value, as previously found in other FSRQ [10][13]. We propose that these features are the signature of bulk Comptonization of soft X-ray photons.