THE X-RAY-SPECTRUM OF MCG-6-30-15 AND ITS TEMPORAL VARIABILITY

Ginga observations of the Seyfert I galaxy MCG-6-30-15 show rapid variability consistent with that found by EXOSAT and the greater sensitivity afforded by the larger detector area and low background of the LAC confirm and extend the spectral detail seen previously. In addition, time-resolved X-ray spectroscopy shows short time-scale variability of the continuum spectrum, primarily at low X-ray energies and in the sense that the softness increases with flux. We find that the X-ray data may be explained by a model in which an accretion disc surrounds the central black hole in MCG-6-30-15, above which exists an optically thin continuum source. Spectral features are introduced into the continuum spectrum, arising from reflection and fluorescence when hard X-rays illuminate the disc. This is seen through an outer photo-ionized absorbing screen, which further modifies the observed spectrum. © Royal Astronomical Society.