  We present the broad band analysis of two BeppoSAX observations of the Sy 1
Mkn509. In 2000 the source was in a typical flux state,
F{2-10keV}=2.7x10^{-11}erg cm^{-2} s^{-1}, while in 1998 it was found in a high
flux state, F{2-10keV}=5.7x10^{-11} erg cm^{-2} s^{-1}. A comparison between
the two states shows a energy-dependent flux variation. A soft excess, a narrow
iron line and a Compton reflection hump above 10 keV, are clearly apparent in
the residuals after fitting the spectra with a simple power law. We tested two
alternative models. In the first the iron line and the high energy bump are
well reproduced by reprocessing in a cold and Compton thick material. The
intensity of the iron line (also consistent with a Chandra measurement) as well
as the normalization of the reflection hump are consistent with a constant in
the two epochs: this, combined with the fact that the line is narrow as
observed by Chandra, suggests a common origin from distant and optically thick
matter. This model further requires a component to model the soft excess: the
empirical choice of two black bodies accounts well for the excess in both
observations, their combined strength was a factor about three higher in the
high than in the low flux state defined above. However the relative
contribution of the soft excess is higher in the low flux state. In the second
model we attempted to reproduce all spectral features, except for the narrow
cold line, with reflection from an ionized disc. This model is successful only
in the high flux state,but it fails in the low flux state, when the soft excess
is only partially accounted for. In either models, the slope of the power law
is larger in the high than in the low flux state, in agreement with a behaviour
known to be shared by several objects of the same type.
