A possible interpretation of the Seyfert-like component in 3C 273 X-ray spectrum

¹ Dipartimento di Astronomia e Scienza dello Spazio, Largo E. Fermi 2, 50125 Firenze, Italy e-mail: paola@arcetri.astro.it
² INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy e-mail: torricel@arcetri.astro.it

Received: 3 April 2007
Accepted: 29 October 2007

Abstract

Context.Recent studies of the X-ray spectrum of the quasar 3C 273, analyzing both BeppoSAX data and XMM-Newton data, have shown that, depending on the state of the source, Seyfert-like spectral features, including a significant soft excess, can be detected superimposed on the generally overwhelming beamed non-thermal emission (“jet” component).

Aims.In order to explain the Seyfert-like component and the soft excess suggested by the X-ray spectrum analysis, we apply to 3C 273 a recently developed model for non-thermal emission of X-rays from AGN disk coronae, originally intended for the explanation of Seyfert type X-ray emission.

Methods.We perform an analysis of BeppoSAX data at different epochs, fitting the spectrum with a composition of a beamed “jet” component and our coronal model with a reflected component and an iron emission line.

Results. We obtained reasonable fits of BeppoSAX spectra at different epochs by changing the relative weight of our emission model and of the jet power-law component. We find that in all these cases the low energy (2 keV) part of the X-ray spectrum is accounted for by our Seyfert-like model; we also verify the existence of a positive correlation between the Seyfert-like component 2–10 keV flux and the 0.2–2 keV flux of the so-called soft excess.

Conclusions.The results outlined above confirm the plausibility of our non-thermal flare-like coronal model as a possible interpretation of Seyfert-like emission in AGNs. We can conclude that the interpretation of the Seyfert-like component in terms of our non-thermal corona model is offering, as a natural result, a description of the soft excess origin, which is still the subject of lively debate.