Multiwavelength campaign on Mrk 509

P.-O Petrucci,M Dadina,M Mehdipour,S Bianchi,S Paltani,J Malzac,G A Kriss,G Branduardi-Raymont,K C Steenbrugge,G Ponti,J S Kaastra,E Costantini,P Lubiński,M Cappi,B De Marco

doi:10.1051/0004-6361/201219956

Abstract

(Abridged) The simultaneous UV to X-rays/gamma rays data obtained during the multi-wavelength XMM/INTEGRAL campaign on the Seyfert 1 Mrk 509 are used in this paper and tested against physically motivated broad band models. Each observation has been fitted with a realistic thermal comptonisation model for the continuum emission. Prompted by the correlation between the UV and soft X-ray flux, we use a thermal comptonisation component for the soft X-ray excess. The UV to X-rays/gamma-rays emission of Mrk 509 can be well fitted by these components. The presence of a relatively hard high-energy spectrum points to the existence of a hot (kT~100 keV), optically-thin (tau~0.5) corona producing the primary continuum. On the contrary, the soft X-ray component requires a warm (kT~1 keV), optically-thick (tau~15) plasma. Estimates of the amplification ratio for this warm plasma support a configuration close to the "theoretical" configuration of a slab corona above a passive disk. An interesting consequence is the weak luminosity-dependence of its emission, a possible explanation of the roughly constant spectral shape of the soft X-ray excess seen in AGNs. The temperature (~ 3 eV) and flux of the soft-photon field entering and cooling the warm plasma suggests that it covers the accretion disk down to a transition radius $R_{tr}$ of 10-20 $R_g$. This plasma could be the warm upper layer of the accretion disk. On the contrary the hot corona has a more photon-starved geometry. The high temperature ($\sim$ 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 comptonised emission produced by the warm plasma. In this framework, the change in the geometry (i.e. $R_{tr}$) could explain most of the observed flux and spectral variability.

Highlights

Each observation has been fitted with a realistic thermal Comptonization model for the continuum emission
An interesting consequence is the weak luminosity-dependence of its emission, which is a possible explanation of the roughly constant spectral shape of the soft X-ray excess seen in AGNs
Another important parameter is the geometry of the disk-corona system, which can be related to the amplification ratio

Summary

Introduction

Since the discovery of a high-energy cut-off in the X-ray emission of Seyfert galaxies, first detected by SIGMA and OSSE in NGC 4151 (Jourdain et al 1992; Maisack et al 1993) and commonly observed in about 50% of Seyfert galaxies (Zdziarski et al 1993; Gondek et al 1996; Matt 2001; Perola et al 2002; Deluit & Courvoisier 2003; Dadina 2007; Molina et al 2009), the primary continuum of this class of AGN is commonly believed to be thermal Comptonization of soft seedArticle published by EDP SciencesA73, page 1 of 17A&A 549, A73 (2013)photons produced by a “cold phase”, presumably the accretion disk, on hot (∼100 keV) thermal electrons (the “hot phase” called corona). The nature and origin of this thermal hot plasma are, still largely unknown, mainly owing to the lack of sensitive instruments at high energies. This hinders our ability to put tight constraints on the spectral shape and to disentangle the primary continuum from the reflection component. At lower energies (

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Discussion

Conclusion