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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
Radio-to-UV monitoring of AO 0235+164 by the WEBT and Swift during the 2006-2007 outburst
Astronomy and Astrophysics, Volume 480, No. 2, Year 2008
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Description
Context.The blazar AO 0235+164 was claimed to show a quasi-periodic behaviour in the radio and optical bands in the past, with the main outbursts repeating every 5-6 years. However, the predicted 2004 outburst did not occur, and further analysis suggested a longer time scale, according to which the next event would have occurred in the 2006-2007 observing season. Moreover, an extra emission component contributing to the UV and soft X-ray flux was detected, whose nature is not yet clear. An optical outburst was observed in late 2006-early 2007, which triggered a Whole Earth Blazar Telescope (WEBT) campaign as well as target of opportunity (ToO) observations by the Swift satellite.Aims.In this paper, we present the radio-to-optical data taken by the WEBT together with the UV data acquired by the UltraViolet and Optical Telescope (UVOT) instrument onboard Swift to investigate both the outburst behaviour at different wavelengths and the nature of the extra emission component.Methods. Multifrequency light curves have been assembled with data from 27 observatories; optical and UV fluxes have been cleaned from the contamination of the southern active galactic nucleus (AGN). We have analysed spectral energy distributions at different epochs, corresponding to different brightness states; extra absorption by the foreground galaxy has been taken into account.Results.We found the optical outburst to be as strong as the big outbursts of the past: starting from late September 2006, a brightness increase of ~5 mag led to the outburst peak in February 19-21, 2007. We also observed an outburst at mm and then at cm wavelengths, with an increasing time delay going toward lower frequencies during the rising phase. Cross-correlation analysis indicates that the 1 mm and 37 GHz flux variations lagged behind the -band ones by about 3 weeks and 2 months, respectively. These short time delays suggest that the corresponding jet emitting regions are only slightly separated and/or misaligned. In contrast, during the outburst decreasing phase the flux faded contemporaneously at all cm wavelengths. This abrupt change in the emission behaviour may suggest the presence of some "shutdown" mechanism of intrinsic or geometric nature. The behaviour of the UV flux closely follows the optical and near-IR one. By separating the synchrotron and extra component contributions to the UV flux, we found that they correlate, which suggests that the two emissions have a common origin. © 2008 ESO.
Authors & Co-Authors
Raiteri, Claudia M.
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Villata, Massimo
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Larionov, Valeri M.
Russian Federation, Saint Petersburg
Saint Petersburg State University
Russian Federation, Saint Petersburg
Pulkovo Observatory of the Russian Academy of Sciences
Aller, M. F.
United States, Ann Arbor
University of Michigan, Ann Arbor
Bach, Uwe
Germany, Bonn
Max Planck Institute for Radio Astronomy
Gurwell, Mark A.
United States, Cambridge
Harvard-smithsonian Center for Astrophysics
Kurtanidze, Omar M.
Georgia, Abastumani
Abastumani Astrophysical Observatory
L¨ahteenm¨aki, Anne A.
Finland, Espoo
Aalto University
Nilsson, Kari
Finland, Turku
Turun Yliopisto
Volvach, A. E.
Ukraine, Bakhchysarai
Crimean Astrophysical Observatory Ras
Aller, Hugh D.
United States, Ann Arbor
University of Michigan, Ann Arbor
Arkharov, Arkady A.H.
Russian Federation, Saint Petersburg
Pulkovo Observatory of the Russian Academy of Sciences
Bachev, Rumen S.
Bulgaria, Sofia
The Bulgarian Academy of Sciences
Berdyugin, Andrei V.
Finland, Turku
Turun Yliopisto
Boettcher, M.
United States, Athens
Ohio University
Buemi, Carla S.
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Calcidese, Paolo
Unknown Affiliation
Di Paola, Andrea
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Forné, E.
Unknown Affiliation
Foschini, Luigi
Italy, Bologna
Inaf Istituto Di Astrofisica Spaziale e Fisica Cosmica, Bologna
Gupta, Alok Chandra
China, Beijing
Chinese Academy of Sciences
Hovatta, Talvikki
Finland, Espoo
Aalto University
Joshi, Manasvita
United States, Athens
Ohio University
Kadler, Matthias L.
United States, Greenbelt
Nasa Goddard Space Flight Center
Grishina, Tatiana S.
Russian Federation, Saint Petersburg
Saint Petersburg State University
Kostov, Andon B.
Unknown Affiliation
Krichbaum, Thomas P.
Germany, Bonn
Max Planck Institute for Radio Astronomy
Lanteri, Luciano
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Larionova, Liudmilla V.
Russian Federation, Saint Petersburg
Saint Petersburg State University
Lee, Chung-uk
South Korea, Daejeon
Korea Astronomy and Space Science Institute
Leto, Paolo
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Lindfors, Elina J.
Finland, Turku
Turun Yliopisto
Nesci, Roberto
Italy, Rome
Sapienza Università Di Roma
Nieppola, Elina
Finland, Espoo
Aalto University
Nikolashvili, M. G.
Georgia, Abastumani
Abastumani Astrophysical Observatory
Ohlert, Johannes M.
Germany
Michael Adrian Observatory
Oksanen, Arto
Finland, Hankasalmi
Hankasalmen Observatorion
Ovcharov, E.
Bulgaria, Sofia
Sofia University St. Kliment Ohridski
Pääkkönen, Pertti
Finland, Kuopio
Itä-suomen Yliopisto
Pasanen, Mikko
Finland, Turku
Turun Yliopisto
Pursimo, Tapio
Spain, Brena Baja
Nordic Optical Telescope
Ros, J. A.
Unknown Affiliation
Semkov, Evgeni H.
Bulgaria, Sofia
The Bulgarian Academy of Sciences
Smart, Richard L.
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Strigachev, Anton A.
Bulgaria, Sofia
The Bulgarian Academy of Sciences
Takalo, Leo O.
Finland, Turku
Turun Yliopisto
Torii, Ken'ichi N.Ichi
Japan, Suita
Osaka University
Tornikoski, Merja
Finland, Espoo
Aalto University
Trigilio, Corrado
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Umana, Grazia
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Valcheva, Antoniya T.
Bulgaria, Sofia
The Bulgarian Academy of Sciences
Bulgaria, Sofia
Sofia University St. Kliment Ohridski
Statistics
Citations: 53
Authors: 51
Affiliations: 24
Identifiers
Doi:
10.1051/0004-6361:20079044
ISSN:
14320746
Research Areas
Environmental
Study Approach
Quantitative