First constraints on iron abundance versus reflection fraction from the Seyfert 1 galaxy MCG-6-30-15

We report on a joint ASCA and RXTE observation spanning an similar to 400 ks time interval of the bright Seyfert 1 galaxy MCG-6-30-15. The data clearly confirm the presence of a broad skewed iron line (W-K alpha similar to 266 eV) and Compton reflection continuum at higher energies reported in our previous paper. We also investigate whether the gravitational and Doppler effects, which affect the iron line, may also be manifest in the reflected continuum. The uniqueness of this data set is underlined by the extremely good statistics that we obtain from the approximately four million photons that make up the 2-20 keV RXTE PCA spectrum alone. This, coupled with the high energy coverage of HEXTE and the spectral resolution of ASCA in the iron line regime, has allowed us to constrain the relationship between abundance and reflection fraction for the first time at the 99 per cent confidence level. The reflection fraction is entirely consistent with a flat disc, i.e. the cold material subtends 2 pi sr at the source, to an accuracy of 20 per cent. Monte Carlo simulations show that the observed strong iron line intensity is explained by an overabundance of iron by a factor of similar to 2 and an underabundance of the lower-Z elements by a similar factor. By considering non-standard abundances, a clear and consistent picture can be made in which both the iron line and reflection continuum come from the same material such as, e.g., an accretion disc.