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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
A new activity phase of the blazar 3C 454.3: Multifrequency observations by the WEBT and XMM-Newton in 2007-2008
Astronomy and Astrophysics, Volume 491, No. 3, Year 2008
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Description
Aims. The Whole Earth Blazar Telescope (WEBT) consortium has been monitoring the blazar 3C 454.3 from the radio to the optical bands since 2004 to study its emission variability properties.Methods. We present and analyse the multifrequency results of the 2007-2008 observing season, including XMM-Newton observations and near-IR spectroscopic monitoring, and compare the recent emission behaviour with the past one. The historical mm light curve is presented here for the first time.Results. In the optical band we observed a multi-peak outburst in July-August 2007, and other faster events in November 2007-February 2008. During these outburst phases, several episodes of intranight variability were detected. A mm outburst was observed starting from mid 2007, whose rising phase was contemporaneous to the optical brightening. A slower flux increase also affected the higher radio frequencies, the flux enhancement disappearing below 8 GHz. The analysis of the optical-radio correlation and time delays, as well as the behaviour of the mm light curve, confirm our previous predictions, suggesting that changes in the jet orientation likely occurred in the last few years. The historical multiwavelength behaviour indicates that a significant variation in the viewing angle may have happened around year 2000. Colour analysis confirms a general redder-when-brighter trend, which reaches a "saturation" at R ∼ 14 and possibly turns into a bluer-when-brighter trend in bright states. This behaviour is due to the interplay of different emission components, the synchrotron one possibly being characterised by an intrinsically variable spectrum. All the near-IR spectra show a prominent Hα emission line (EWobs = 50-120 Å), whose flux appears nearly constant, indicating that the broad line region is not affected by the jet emission. We show the broad-band SEDs corresponding to the epochs of the XMM-Newton pointings and compare them to those obtained at other epochs, when the source was in different brightness states. A double power-law fit to the EPIC spectra including extra absorption suggests that the soft-X-ray spectrum is concave, and that the curvature becomes more pronounced as the flux decreases. This connects fairly well with the UV excess, which becomes more prominent with decreasing flux. The most obvious interpretation implies that, as the beamed synchrotron radiation from the jet dims, we can see both the head and the tail of the big blue bump. The X-ray flux correlates with the optical flux, suggesting that in the inverse-Compton process either the seed photons are synchrotron photons at IR-optical frequencies or the relativistic electrons are those that produce the optical synchrotron emission. The X-ray radiation would thus be produced in the jet region from where the IR-optical emission comes.. © 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
Gurwell, Mark A.
United States, Cambridge
Harvard-smithsonian Center for Astrophysics
Chen, Wenping
Taiwan, Taoyuan
National Central University
Kurtanidze, Omar M.
Georgia, Abastumani
Abastumani Astrophysical Observatory
Aller, M. F.
United States, Ann Arbor
University of Michigan, Ann Arbor
Boettcher, M.
United States, Athens
Ohio University
Calcidese, Paolo
Italy, Nus
Osservatorio Astronomico Della Regione Autonoma Valle D'aosta
Hroch, Filip
Czech Republic, Brno
Masaryk University
L¨ahteenm¨aki, Anne A.
Finland, Espoo
Aalto University
Lee, Chung-uk
South Korea, Daejeon
Korea Astronomy and Space Science Institute
Nilsson, Kari
Finland, Turku
Turun Yliopisto
Ohlert, Johannes M.
Germany
Michael Adrian Observatory
Papadakis, Iossif E.
Greece, Heraklion
Foundation for Research and Technology-hellas
Greece, Rethymnon
University of Crete
Agudo, Iván N.
Spain, Madrid
Consejo Superior de Investigaciones Científicas
Aller, Hugh D.
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
Bachev, Rumen S.
Bulgaria, Sofia
The Bulgarian Academy of Sciences
Berdyugin, Andrei V.
Finland, Turku
Turun Yliopisto
Buemi, Carla S.
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Carosati, Daniele
Italy
Armenzano Astronomical Observatory
Charlot, Patrick
France, Bordeaux
Université de Bordeaux
France, Paris
Cnrs Centre National de la Recherche Scientifique
Chatzopoulos, Emmanouil
Greece, Rethymnon
University of Crete
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
Gupta, Alok Chandra
Unknown Affiliation
Jorstad, Svetlana G.
United States, Boston
Boston University
Grishina, Tatiana S.
Russian Federation, Saint Petersburg
Saint Petersburg State University
Kopatskaya, Evgenia N.
Russian Federation, Saint Petersburg
Saint Petersburg State University
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
Latev, Georgi Y.
Bulgaria, Sofia
Sofia University St. Kliment Ohridski
Le Campion, Jean François
France, Bordeaux
Université de Bordeaux
France, Paris
Cnrs Centre National de la Recherche Scientifique
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
McBreen, Brian
Ireland, Dublin
University College Dublin
Mihov, Boyko M.
Bulgaria, Sofia
The Bulgarian Academy of Sciences
Nesci, Roberto
Italy, Rome
Sapienza Università Di Roma
Nikolashvili, M. G.
Georgia, Abastumani
Abastumani Astrophysical Observatory
Novák, Rudolf
Unknown Affiliation
Ovcharov, E.
Bulgaria, Sofia
Sofia University St. Kliment Ohridski
Pian, Elena
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Principe, David A.
United States, Athens
Ohio University
Pursimo, Tapio
Spain, Brena Baja
Nordic Optical Telescope
Ros, J. A.
Unknown Affiliation
Sadun, Alberto C.
United States, Denver
University of Colorado Denver
Sagar, Ram
Unknown Affiliation
Semkov, Evgeni H.
Bulgaria, Sofia
The Bulgarian Academy of Sciences
Smart, Richard L.
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Smith, Niall J.
Ireland, Bishopstown
Munster Technological University Mtu
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
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: 82
Authors: 68
Affiliations: 31
Identifiers
Doi:
10.1051/0004-6361:200810869
ISSN:
14320746
Research Areas
Cancer
Environmental
Study Approach
Qualitative