Multiwavelength campaign on Mrk 509
XII. Broad band spectral analysis
1 UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, 38041 Grenoble, France
2 ISDC Data Centre for Astrophysics, Astronomical Observatory of the University of Geneva, 16 Ch. d’Ecogia, 1290 Versoix, Switzerland
3 Université de Toulouse, UPS-OMP, IRAP, Toulouse, France
4 CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
5 SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
6 Sterrenkundig Instituut, Universiteit Utrecht, PO Box 80000, 3508 TA Utrecht, The Netherlands
7 INAF – IASF Bologna, via Gobetti 101, 40129 Bologna, Italy
8 School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ, UK
9 Centro de Astrobiología (CSIC-INTA), Dep. de Astrofísica; LAEFF, PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain
10 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
11 Department of Physics and Astronomy, The John Hopkins University, Baltimore, MD 21218, USA
12 Instituto de Astronomía, Universidad Católica del Norte, Avenida Angamos 0610, Casilla 1280, Antofagasta, Chile
13 Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UK
14 Dipartimento di Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
15 Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK
16 Centrum Astronomiczne im. M. Kopernika, Rabiańska 8, 87-100 Toruń, Poland
Received: 6 July 2012
Accepted: 23 September 2012
The origin of the different spectral components present in the high-energy (UV to X-rays/gamma-rays) spectra of Seyfert galaxies is still being debated a lot. One of the major limitations, in this respect, is the lack of really simultaneous broad-band observations that allow us to disentangle the behavior of each component and to better constrain their interconnections. The simultaneous UV to X-rays/gamma rays data obtained during the multiwavelength campaign on the bright Seyfert 1 Mrk 509 are used in this paper and tested against physically motivated broad band models.
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. We also included a warm absorber and a reflection component, as required by the precise studies previously done by our consortium. The UV to X-ray/gamma-ray 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 (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. 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. 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 Rin of 10 − 20 Rg. 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. In this framework, the change in the geometry (i.e. Rin) could explain most of the observed flux and spectral variability.
Key words: galaxies: active / galaxies: individual: Mrk 509 / galaxies: Seyfert / X-rays: galaxies
© ESO, 2012