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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
The high activity of 3C 454.3 in autumn 2007: Monitoring by the WEBT during the AGILE detection
Astronomy and Astrophysics, Volume 485, No. 2, Year 2008
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Description
Context. The quasar-type blazar 3C 454.3 underwent a phase of high activity in summer and autumn 2007 that was intensively monitored in the radio-to-optical bands by the Whole Earth Blazar Telescope (WEBT). The -ray satellite Astro-rivelatore Gamma a Immagini LEggero (AGILE) detected this source first in late July, and then in November-December 2007.Aims. We present the multifrequency data collected by the WEBT and collaborators during the second AGILE observing period, complemented by contemporaneous data from the UltraViolet and Optical Telescope (UVOT) onboard the Swift satellite. The aim is to trace in detail the behaviour of the synchrotron emission from the blazar jet, and to investigate the contribution from the thermal emission component.Methods. Optical data from about twenty telescopes have been homogeneously calibrated and carefully assembled to construct an -band light curve containing about 1340 data points over 42 days. This extremely well-sampled optical light curve allows us to follow the dramatic flux variability of the source in detail. In addition, we show radio-to-UV spectral energy distributions (SEDs) at different epochs, which represent different brightness levels.Results. In the considered period, the source varied by 2.6 mag over two weeks in the band. Many episodes of fast (i.e. intranight) variability were observed, most notably on December 12, when a flux increase of about 1.1 mag in 1.5 h was detected, followed by a steep decrease of about 1.2 mag in 1 h. The contribution by the thermal component is difficult to assess, due to the uncertainties in the Galactic, and possibly also intrinsic, extinction in the band. However, polynomial fitting of radio-to-UV SEDs reveals an increasing spectral bending towards fainter states, suggesting a UV excess likely due to the thermal emission from the accretion disc.Conclusions. Once the AGILE data are completely analysed, the low-frequency observations presented in this letter will offer a powerful tool to investigate optical- flux correlations, i.e. the relationship between the synchrotron and inverse-Compton emission components. © 2008 ESO.
Authors & Co-Authors
Raiteri, Claudia M.
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Villata, Massimo
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Chen, Wenping
Taiwan, Taoyuan
National Central University
Kurtanidze, Omar M.
Georgia, Abastumani
Abastumani Astrophysical Observatory
Nilsson, Kari
Finland, Turku
Turun Yliopisto
Larionov, Valeri M.
Russian Federation, Saint Petersburg
Saint Petersburg State University
Russian Federation, Saint Petersburg
Pulkovo Observatory of the Russian Academy of Sciences
Gurwell, Mark A.
United States, Cambridge
Harvard-smithsonian Center for Astrophysics
Agudo, Iván N.
Spain, Madrid
Consejo Superior de Investigaciones Científicas
Aller, Hugh D.
United States, Ann Arbor
University of Michigan, Ann Arbor
Aller, M. F.
United States, Ann Arbor
University of Michigan, Ann Arbor
Angelakis, Emmanouil
Germany, Bonn
Max Planck Institute for Radio Astronomy
Arkharov, Arkady A.H.
Russian Federation, Saint Petersburg
Pulkovo Observatory of the Russian Academy of Sciences
Bach, Uwe
Germany, Bonn
Max Planck Institute for Radio Astronomy
Boettcher, M.
United States, Athens
Ohio University
Buemi, Carla S.
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Calcidese, Paolo
Italy, Nus
Osservatorio Astronomico Della Regione Autonoma Valle D'aosta
Charlot, Patrick
France, Pessac
Laboratoire D'astrophysique de Bordeaux
D'Ammando, Filippo
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Donnarumma, Immacolata
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Forné, E.
Unknown Affiliation
Frasca, Antonio
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Fuhrmann, Lars
Germany, Bonn
Max Planck Institute for Radio Astronomy
Gómez, Jose L.
Spain, Madrid
Consejo Superior de Investigaciones Científicas
Jorstad, Svetlana G.
United States, Boston
Boston University
Kimeridze, Givi N.
Georgia, Abastumani
Abastumani Astrophysical Observatory
Krichbaum, Thomas P.
Germany, Bonn
Max Planck Institute for Radio Astronomy
L¨ahteenm¨aki, Anne A.
Finland, Espoo
Aalto University
Lanteri, Luciano
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Latev, Georgi Y.
Bulgaria, Sofia
Sofia University St. Kliment Ohridski
Le Campion, Jean François
France, Pessac
Laboratoire D'astrophysique de Bordeaux
Lee, Chung-uk
South Korea, Daejeon
Korea Astronomy and Space Science Institute
Leto, Paolo
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Lin, Hungchin
Taiwan, Taoyuan
National Central University
Marchili, Nicola
Germany, Bonn
Max Planck Institute for Radio Astronomy
Marscher, Alan P.
United States, Boston
Boston University
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
Ovcharov, E.
Bulgaria, Sofia
Sofia University St. Kliment Ohridski
Principe, David A.
United States, Athens
Ohio University
Pursimo, Tapio
Spain, Brena Baja
Nordic Optical Telescope
Sadun, Alberto C.
United States, Denver
University of Colorado Denver
Sigua, Lorand A.
Georgia, Abastumani
Abastumani Astrophysical Observatory
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
Tavani, Marco
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Thum, Clemens
Unknown Affiliation
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
Vercellone, Stefano
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Volvach, A. E.
Ukraine, Bakhchysarai
Crimean Astrophysical Observatory Ras
Wiesemeyer, Helmut W.
Unknown Affiliation
Statistics
Citations: 54
Authors: 56
Affiliations: 23
Identifiers
Doi:
10.1051/0004-6361:200809995
ISSN:
14320746
Research Areas
Environmental