Free access article

A&A 451, L1-L4 (2006)
DOI: 10.1051/0004-6361:200600023

Letter

A historic jet-emission minimum reveals hidden spectral features in 3C 273

M. Türler^{1, 2}, M. Chernyakova^{1, 2}, T. J.-L. Courvoisier^{1, 2}, C. Foellmi³, M. F. Aller⁴, H. D. Aller⁴, A. Kraus⁵, T. P. Krichbaum⁵, A. Lähteenmäki⁶, A. Marscher⁷, I. M. McHardy⁸, P. T. O'Brien⁹, K. L. Page⁹, L. Popescu^{1, 2}, E. I. Robson¹⁰, M. Tornikoski⁶ and H. Ungerechts<sup>11

1</sup>  INTEGRAL Science Data Centre, Ch. d'Ecogia 16, 1290 Versoix, Switzerland
    e-mail: Marc.Turler@obs.unige.ch
²  Geneva Observatory, Ch. des Maillettes 51, 1290 Sauverny, Switzerland
³  European Southern Observatory, Alonso de Cordova 3107, Vitacura, casilla 19 001, Santiago, Chile
⁴  University of Michigan, Department of Astronomy, 817 Dennison Building, Ann Arbor MI, 48 109 USA
⁵  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53 121 Bonn, Germany
⁶  Metsähovi Radio Observatory, Helsinki University of Technology, Metsähovintie, 02 540 Kylmälä, Finland
⁷  Institute for Astrophysical Research, Boston Univ., 725 Commonwealth Ave., Boston MA, 02 215, USA
⁸  School of Physics and Astronomy, The University, Southampton SO17 1BJ, UK
⁹  Department of Physics & Astronomy, University of Leicester, Leicester LE1 7RH, UK
¹⁰  UK Astronomy Technology Centre, Royal Observatory Edinburgh, EH9 3HJ, UK
¹¹  Institut de Radio Astronomie Millimétrique (IRAM), Avd. Div. Pastora 7NC, 18 012 Granada, Spain

(Received 9 December 2005 / Accepted 20 March 2006 )

Abstract
Aims. The aim of this work is to identify and study spectral features in the quasar 3C 273 usually blended by its strong jet emission.
Methods. A historic minimum in the sub-millimetre emission of 3C 273 triggered coordinated multi-wavelength observations in June 2004. X-ray observations from the INTEGRAL, XMM-Newton and RXTE satellites are complemented by ground-based optical, infrared, millimetre and radio observations. The overall spectrum is used to model the infrared and X-ray spectral components.
Results. Three thermal dust emission components are identified in the infrared. The dust emission on scales from 1 pc to several kpc is comparable to that of other quasars, as expected by AGN unification schemes. The observed weakness of the X-ray emission supports the hypothesis of a synchrotron self-Compton origin for the jet component. There is a clear soft-excess and we find evidence for a very broad iron line which could be emitted in a disk around a Kerr black hole. Other signatures of a Seyfert-like X-ray component are not detected.

Key words: quasars: general -- quasars: individual: 3C 273 -- infrared: galaxies -- X-rays: galaxies

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© ESO 2006

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