%P - %L discovery1420273 %T Multiwavelength campaign on Mrk 509: testing realistic comptonization models %D 2012 %O © 2012 The Authors. Publication available under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 licence (CC BY-NC-SA) described at http://creativecommons.org/licenses/by-nc-sa/3.0/. %A G Branduardi Raymont %A PO Petrucci %A S Paltani %A J Malzac %A J Kaastra %A M Cappi %A G Ponti %A B de Marco %A G Kriss %A K Steenbrugge %A S Bianchi %A M Mehdipour %A E Costantini %A M Dadina %A P Lubinski %X Mrk 509 was observed by XMM-Newton and INTEGRAL in October/November 2009, with one observation every four days for a total of ten observations. Each observation has been fitted with a realistic thermal Comptonization model for the continuum emission. Prompted by the correlation between the UV and soft X-ray flux, we used a thermal Comptonization component for the soft X-ray excess. The UV to X-ray/gamma-ray emission of Mrk 509 can be well fitted by these components, pointing to the existence of a hot (kT ∼ 100 keV), optically-thin (τ ∼ 0.5) corona producing the primary continuum. In contrast, the soft X-ray component requires a warm (kT ∼ 1 keV), optically-thick (τ ∼ 10-20) plasma. Estimates of the amplification ratio for this warm plasma support a configuration relatively close to the “theoretical†configuration of a slab corona above a passive disk. This plasma could be the warm upper layer of the accretion disk. In contrast, the hot corona has a more photon-starved geometry. The high temperature (∼ 100 eV) of the soft-photon field entering and cooling it favors a localization of the hot corona in the inner flow. This soft-photon field could be part of the comptonized emission produced by the warm plasma. %C Paris, France %B Proceedings of 'An INTEGRAL view of the high-energy sky (the first 10 years)' - 9th INTEGRAL Workshop and celebration of the 10th anniversary of the launch (INTEGRAL 2012)