Volume 453, Number 3, July III 2006
|Page(s)||817 - 822|
|Published online||28 June 2006|
The unprecedented optical outburst of the quasar 3C 454.3
The WEBT campaign of 2004–2005
INAF, Osservatorio Astronomico di Torino, Italy e-mail: firstname.lastname@example.org
2 Foggy Bottom Observatory, Colgate University, NY, USA
3 Department of Astronomy, University of Michigan, MI, USA
4 Institute for Astrophysical Research, Boston University, MA, USA
5 Abastumani Astrophysical Observatory, Georgia
6 Astrophysikalisches Institut Potsdam, Germany
7 Landessternwarte Heidelberg-Königstuhl, Germany
8 Harvard-Smithsonian Center for Astrophysics, MA, USA
9 Instituto de Astronomía, UNAM, Mexico
10 INAF, Osservatorio Astronomico di Roma, Italy
11 Tuorla Observatory, Finland
12 Astronomical Institute, Osaka Kyoiku University, Japan
13 Main (Pulkovo) Astronomical Observatory of the Russian Academy of Sciences, Russia
14 INAF, Osservatorio Astrofisico di Catania, Italy
15 Astrophysical Institute, Department of Physics and Astronomy, Ohio University, OH, USA
16 Armenzano Astronomical Observatory, Italy
17 Agrupació Astronòmica de Sabadell, Spain
18 Institute of Astronomy, National Central University, Taiwan
19 Dipartimento di Fisica e Osservatorio Astronomico, Università di Perugia, Italy
20 INAF, Osservatorio Astronomico di Teramo, Italy
21 Departamento de Astrofísica, Universidad Complutense, Spain
22 Astronomical Institute, St.-Petersburg State University, Russia
23 Isaac Newton Institute of Chile, St.-Petersburg Branch, Russia
24 Institute of Theoretical Physics and Astrophysics, Masaryk University, Czech Republic
25 Astronomical Institute, Academy of Sciences of the Czech Republic, Czech Republic
26 Ulugh Beg Astronomical Institute, Academy of Sciences of Uzbekistan, Uzbekistan
27 Department of Astronomy, Kyoto University, Japan
28 Jansky fellow, National Radio Astronomy Observatory, WV, USA
29 Astro Space Center of Lebedev Physical Institute, Russia
30 Max-Planck-Institut für Radioastronomie, Germany
31 Division of Astronomy, University of Oulu, Finland
32 Korea Astronomy and Space Science Institute, South Korea
33 INAF, Istituto di Radioastronomia Sezione di Noto, Italy
34 Metsähovi Radio Observatory, Helsinki University of Technology, Finland
35 Instituto Nacional de Astrofísica, Optica y Electrónica (INAOE), Mexico
36 School of Physics and Astronomy, The University, UK
37 Michael Adrian Observatory, Germany
38 Nordic Optical Telescope, Roque de los Muchachos Astronomical Observatory, TF, Spain
39 Department of Physics, University of Colorado at Denver and Health Sciences Center, CO, USA
40 Crimean Astrophysical Observatory, Ukraine
41 Radio Astronomy Laboratory of Crimean Astrophysical Observatory, Ukraine
42 Institut für Theoretische Physik und Astrophysik der Universität Kiel, Germany
Accepted: 2 March 2006
Context.The radio quasar 3C 454.3 underwent an exceptional optical outburst lasting more than 1 year and culminating in spring 2005. The maximum brightness detected was , which represents the most luminous quasar state thus far observed ().
Aims.In order to follow the emission behaviour of the source in detail, a large multiwavelength campaign was organized by the Whole Earth Blazar Telescope (WEBT).
Methods.Continuous optical, near-IR and radio monitoring was performed in several bands. ToO pointings by the Chandra and INTEGRAL satellites provided additional information at high energies in May 2005.
Results.The historical radio and optical light curves show different behaviours. Until about 2001.0 only moderate variability was present in the optical regime, while prominent and long-lasting radio outbursts were visible at the various radio frequencies, with higher-frequency variations preceding the lower-frequency ones. After that date, the optical activity increased and the radio flux is less variable. This suggests that the optical and radio emissions come from two separate and misaligned jet regions, with the inner optical one acquiring a smaller viewing angle during the 2004-2005 outburst. Moreover, the colour-index behaviour (generally redder-when-brighter) during the outburst suggests the presence of a luminous accretion disc. A huge mm outburst followed the optical one, peaking in June-July 2005. The high-frequency (37-43 GHz) radio flux started to increase in early 2005 and reached a maximum at the end of our observing period (end of September 2005). VLBA observations at 43 GHz during the summer confirm the brightening of the radio core and show an increasing polarization. An exceptionally bright X-ray state was detected in May 2005, corresponding to the rising mm flux and suggesting an inverse-Compton nature of the hard X-ray spectrum.
Conclusions.A further multifrequency monitoring effort is needed to follow the next phases of this unprecedented event.
Key words: galaxies: active / galaxies: quasars: general / galaxies: quasars: individual: 3C 454.3 / galaxies: jets
© ESO, 2006
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