Compton reflection and iron fluorescence in BeppoSAX observationsof Seyfert type 1 galaxies

Abstract

A sample of nine bright Seyfert 1 and NELG type galaxies, observed with BeppoSAX, is analyzed to assess on a truly broad band basis (0.1–200 keV) the issue of the spectral contributions of Compton reflection and iron line fluorescence from circumnuclear gas. The empirical description adopted for the direct continuum is the commonly used power law with an exponential cut–off. The most direct test of the theoretical predictions, namely that the equivalent width of the line, $W_{\alpha}$, and the strength R of the reflection relative to the direct continuum are closely related to each other, gives a substantially positive result, that is their mean ratio is very close to expectation, and only a modest spread in the iron abundance seems implied. The existence of a steep correlation between R and the slope Γ of the power law is not confirmed. A weak evidence is found that the existence of a very shallow trend to increase on average with Γ cannot be altogether excluded in both R and $W_{\alpha}$, but needs to be tested with a larger sample. The energy Ef in the exponential cut–off spans a range from about 80 to more than 300 keV. A possible correlation is found, with Ef increasing on average with Γ: if ignored, for instance by keeping Ef at a fixed value in a sample study, it could be cause of artificial steepening in a correlation between R and Γ.