We present the results from a joint Suzaku/NuSTAR broad-band spectral
analysis of 3C 390.3. The high quality data enables us to clearly separate the
primary continuum from the reprocessed components allowing us to detect a high
energy spectral cut-off (Ecut=117−14+18 keV), and to place
constraints on the Comptonization parameters of the primary continuum for the
first time. The hard over soft compactness is 69−24+124 and the optical
depth 4.1−3.6+0.5, this leads to an electron temperature of
30−8+32 keV. Expanding our study of the Comptonization spectrum to the
optical/UV by studying the simultaneous Swift-UVOT data, we find indications
that the compactness of the corona allows only a small fraction of the total
UV/optical flux to be Comptonized. Our analysis of the reprocessed emission
show that 3C 390.3 only has a small amount of reflection (R~0.3), and of that
the vast majority is from distant neutral matter. However we also discover a
soft X-ray excess in the source, which can be described by a weak ionized
reflection component from the inner parts of the accretion disk. In addition to
the backscattered emission, we also detect the highly ionized iron emission
lines Fe XXV and Fe XXVI