NuSTAR, Swift, and GROND observations of the flaring MeV blazar: PMN   J0641$-$0320
  MeV blazars are a sub--population of the blazar family, exhibiting larger--than--average jet powers, accretion luminosities and black hole masses. Because of their extremely hard X--ray continua, these objects are best studied in the X-ray domain. Here, we report on the discovery by the $Fermi$ Large Area Telescope and subsequent follow-up observations with $NuSTAR$, $Swift$ and GROND of a new member of the MeV blazar family: PMN J0641$-$0320. Our optical spectroscopy provides confirmation that this is a flat--spectrum radio quasar located at a redshift of $z=1.196$. Its very hard $NuSTAR$ spectrum (power--law photon index of $\sim$1 up to $\sim$80 keV) indicates that the emission is produced via inverse Compton scattering off photons coming from outside the jet.The overall spectral energy distribution of PMN J0641$-$0320 is typical of powerful blazars and by reproducing it with a simple one-zone leptonic emission model we find the emission region to be located either inside the broad line region or within the dusty torus. 
M. Ajello, G. Ghisellini, V. S. Paliya, D. Kocevski, G. Tagliaferri,   G. Madejski, A. Rau, P. Schady, J. Greiner, F. Massar...
astro-ph.HE astro-ph.CO