Revealing the geometry of the hot corona in NGC 4151

We propose to observe the Seyfert galaxy NGC 4151 with XMMNewton (50 ks) andNuSTAR (100 ks) simultaneously to the scheduled IXPE (Imaging Xray PolarimeterExplorer) pointing. Accurate measurements of the hot corona parameters have beenreported, but no significant constraints on the coronal geometry (slab, sphere,semisphere) have been possible so far. Xray polarimetry has the potentialityto provide such constraints, but the signal is partly degenerate with respect tothe geometrical and physical parameters of the accretion diskcorona system. Toreduce them and constrain the geometrical shape of the corona, simultaneous andindependent constraints on coronal temperature and optical depth, strength ofthe reflection components provided by a joint XMMNewton and NuSTAR observation, are vital. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]