Resolving the large-scale spectral variability of the luminous Seyfert 1 galaxy 1H 0419-577: Evidence for a new emission component and absorption by cold dense matter

An XMM-Newton observation of the luminous Seyfert 1 galaxy 1H 0419-577 in 2002 September, when the source was in an extreme low-flux state, found a very hard X-ray spectrum at 1-10 keV with a strong soft excess below similar to1 keV. Comparison with an earlier XMM-Newton observation when 1H 0419-577 was X-ray bright indicated that the dominant spectral variability was due to a steep power law or cool Comptonized thermal emission. Four further XMM-Newton observations, with 1H 0419-577 in intermediate-flux states, now support that conclusion, while we also find the variable emission component in intermediate-state difference spectra to be strongly modified by absorption in low-ionization matter. The variable soft excess then appears to be an artifact of absorption of the underlying continuum, while the core soft emission can be attributed to recombination in an extended region of more highly ionized gas. We note the wider implications of finding substantial cold dense matter overlying (or embedded in) the X-ray continuum source in a luminous Seyfert 1 galaxy.