2003A&A...401..903G

This paper presents ASCA (July 1997), XMM-Newton (December 2000) and BeppoSAX (January 2001) observations of the Piccinotti Seyfert 1 galaxy ESO 198-G24. The BeppoSAX 0.1-200 keV spectrum exhibits reprocessing features, probably produced by an X-ray illuminated, relativistic accretion disk subtending a solid angle ≲2π. During the XMM-Newton observation the fluorescent iron K_α line profile (centroid energy E_c≃6.4keV) was broad and twice as bright as in the BeppoSAX observation. An additional emission feature (E_c≃5.7keV), detected at the 96.3% confidence level, may be part of a relativistic, double-peaked profile. By contrast, in the earlier ASCA observation the line profile is dominated by a remarkably narrow ``core'' (intrinsic width, σ<50eV). If this component is produced by reflection off the inner surface of a molecular torus, its large Equivalent Width (≃300eV) most likely represents the ``echo'' of a previously brighter flux state, in agreement with the dynamical range covered by the historical X-ray light curve in ESO 198-G24.