THE IRON-K LINE COMPLEX IN NGC-1068 - IMPLICATIONS FOR X-RAY REFLECTION IN THE NUCLEUS

We report a new analysis of ASCA data on the iron K line complex in NG C 1068. The line complex basically consists of three components, as pr eviously reported. A weak red wing of the 6.3-keV fluorescence iron K line is found. A plausible explanation is Compton scattering in optica lly thick, cold matter which can be identified with an obscuring torus or cold gas in the host galaxy. We also show that this 'Compton shoul der' should be observable with ASCA using a simulated reflection spect rum. In order to explain the two higher energy Lines as well as the co ld 6.4-keV line, we fit the ASCA data with a composite model of cold a nd warm reflection. This shows that cold reflection dominates the obse rved X-ray emission above 4 keV; the estimated scattering fraction fro m the warm medium is found to be similar to 0.08 per cent, an order of magnitude below the standard value of I per cent obtained from previo us observations in other wavebands. The two higher energy lines have l arge equivalent width (similar to 3 keV) with respect to the warm-scat tered continuum, suggesting that efficient resonant scattering operate s. The line energies are systematically lower than those expected from resonant lines for Fe XXV and Fe XXVI by similar to 100 eV. The redsh ifts may be due to either the ionized gas of the warm mirror receding at a radial velocity of 4000-5000 km s(-1) or to effects of Compton sc attering in a complicated geometry.