Letter to the Editor
A historic jet-emission minimum reveals hidden spectral features in 3C 273
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
Accepted: 20 March 2006
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.
© ESO, 2006