UNIFIED THEORIES OF ACTIVE GALACTIC NUCLEI - THE HARD X-RAY-SPECTRUM OF NGC-1068

We have reanalysed the Ginga observation of the archetypal Seyfert 2 galaxy NGC 1068. The X-ray spectrum can be decomposed into four components: a hard X-ray power law, iron Kalpha emission-line radiation, reflection from an accretion disc or molecular torus, and emission-line radiation at approximately 8 keV. Although reflection is not required, its inclusion is consistent with the data and increases the underlying intrinsic power-law energy index to alpha(E) approximately 0.9, similar to the typical slope found for Seyfert 1 galaxies. Reflection is unlikely to produce all the observed equivalent width of the Ginga Fe Kalpha emission line, but can account for all of the component seen at 6.4 keV by BBXRT An additional line at approximately 8 keV is required at 95 per cent confidence, and may be identified with a blend of Fe Kbeta and Ni Kalpha lines, or iron recombination radiation. The Ginga data suggest that less than 20 per cent of the 2-10 keV flux is thermal emission with kT greater-than-or-equal-to 2 keV. This favours the proposal of Wilson et al. that the starburst disc spectrum is intrinsically soft, with kT approximately 1 keV, but with a large Fe L emission-line complex giving rise to the apparent hardening in the ROSAT HRI data. If this interpretation is correct then the ratio of equivalent widths of the Fe L and K lines is not a good diagnostic of the ionization state of the scattering region in NGC 1068.