The highly variable X-ray spectrum of the luminous Seyfert 1 galaxy 1H 0419-577

An XMM-Newton observation of the luminous Seyfert 1 galaxy 1H 0419-577 is presented. We find that the spectrum is well fitted by a power law of canonical slope (Γ ~ 1:9) and three blackbody components (to model the strong soft excess). The XMM-Newton data are compared and contrasted with observations by ROSAT in 1992 and by ASCA and BeppoSAX in 1996. We find that the overall X-ray spectrum has changed substantially over the period, and suggest that the changes are driven by the soft X-ray component. When bright, as in our XMM-Newton observation, it appears that the enhanced soft flux cools the Comptonizing corona, causing the 2–10 keV power law to assume a ‘typical’ slope, in contrast to the unusually hard (‘photon-starved’) spectra observed by ASCA and BeppoSAX 4 years earlier.