We present the broad band analysis of two BeppoSAX observations of the Seyfert 1 Mkn 509 .
In 2000 the source was in a typical flux state , F _ { 2 - 10 keV } = 2.7 \times 10 ^ { -11 } erg cm ^ { -2 } s ^ { -1 } , while in 1998 it was found in a high flux state , F _ { 2 - 10 keV } = 5.7 \times 10 ^ { -11 } erg cm ^ { -2 } s ^ { -1 } .
A comparison between the two states shows a energy–dependent flux variation : of about a factor three and a factor two in the LECS ( 0.15-3 keV ) and MECS ( 1.5-10 keV ) , respectively , while in the PDS ( 13-200 keV ) the difference is marginal .
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 , ( \Delta \Gamma \sim 0.2 ) , in agreement with a behaviour known to be shared by several objects of the same type .