This paper presents ASCA ( July 1997 ) , XMM-Newton ( December 2000 ) and BeppoSAX ( January 2001 ) observations of the Piccinotti Seyfert 1 galaxy ESO198-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 \mathrel { \hbox { \hbox to 0.0 pt { \lower 2.365 pt \hbox { $ \sim$ } } \kern - 3.0 pt \raise 1.72 pt \hbox { $ < $ } } } 2 \pi .
During the XMM-Newton observation the fluorescent iron K _ { \alpha } line profile ( centroid energy E _ { c } \simeq 6.4 keV ) was broad and twice as bright as in the BeppoSAX observation .
An additional emission feature ( E _ { c } \simeq 5.7 keV ) , 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 , \sigma < 50 eV ) .
If this component is produced by reflection off the inner surface of a molecular torus , its large Equivalent Width ( \simeq 300 eV ) 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 ESO198-G24 .