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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
WEBT multiwavelength monitoring and XMM-Newton observations of BL Lacertae in 2007-2008
Astronomy and Astrophysics, Volume 507, No. 2, Year 2009
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Description
Context. BL Lacertae is the prototype of the blazar subclass named after it. Yet, it has occasionally shown a peculiar behaviour that has questioned a simple interpretation of its broad-band emission in terms of synchrotron plus synchrotron self-Compton (SSC) radiation.Aims. In the 2007-2008 observing season we carried out a new multiwavelength campaign of the Whole Earth Blazar Telescope (WEBT) on BL Lacertae, involving three pointings by the XMM-Newton satellite in July and December 2007, and January 2008, to study its emission properties, particularly in the optical-X-ray energy range.Methods. The source was monitored in the optical-to-radio bands by 37 telescopes. The brightness level was relatively low. Some episodes of very fast variability were detected in the optical bands. Flux changes had larger amplitude at the higher radio frequencies than at longer wavelengths.Results. The X-ray spectra acquired by the EPIC instrument onboard XMM-Newton are well fitted by a power law with photon index Λ ∼ 2 and photoelectric absorption exceeding the Galactic value. However, when taking into account the presence of a molecular cloud on the line of sight, the EPIC data are best fitted by a double power law, implying a concave X-ray spectrum. The spectral energy distributions (SEDs) built with simultaneous radio-to-X-ray data at the epochs of the XMM-Newton observations suggest that the peak of the synchrotron emission lies in the near-IR band, and show a prominent UV excess, besides a slight soft-X-ray excess. A comparison with the SEDs corresponding to previous observations with X-ray satellites shows that the X-ray spectrum is very variable, since it can change from extremely steep to extremely hard, and can be more or less curved in intermediate states. We ascribe the UV excess to thermal emission from the accretion disc, and the other broad-band spectral features to the presence of two synchrotron components, with their related SSC emission. We fit the thermal emission with a black body law and the non-thermal components by means of a helical jet model. The fit indicates a disc temperature ≳20 000K and a luminosity ≳ 6 × 1044 erg s-1. © 2009 ESO.
Authors & Co-Authors
Raiteri, Claudia M.
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Villata, Massimo
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Capetti, Alessandro
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Aller, M. F.
United States, Ann Arbor
University of Michigan, Ann Arbor
Bach, Uwe
Germany, Bonn
Max Planck Institute for Radio Astronomy
Calcidese, Paolo
Italy, Nus
Osservatorio Astronomico Della Regione Autonoma Valle D'aosta
Gurwell, Mark A.
United States, Cambridge
Harvard-smithsonian Center for Astrophysics
Larionov, Valeri M.
Russian Federation, Saint Petersburg
Saint Petersburg State University
Russian Federation, Saint Petersburg
Pulkovo Observatory of the Russian Academy of Sciences
Ohlert, Johannes M.
Germany
Michael Adrian Observatory
Nilsson, Kari
Finland, Turku
Turun Yliopisto
Strigachev, Anton A.
Bulgaria, Sofia
The Bulgarian Academy of Sciences
Agudo, Iván N.
Spain, Madrid
Consejo Superior de Investigaciones Científicas
Aller, Hugh D.
Mexico, Mexico
Universidad Nacional Autónoma de México
Bachev, Rumen S.
Bulgaria, Sofia
The Bulgarian Academy of Sciences
Benítez, E.
Mexico, Mexico
Universidad Nacional Autónoma de México
Berdyugin, Andrei V.
Finland, Turku
Turun Yliopisto
Boettcher, M.
United States, Athens
Ohio University
Buemi, Carla S.
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Buttiglione, Sara
Italy, Trieste
Scuola Internazionale Superiore Di Studi Avanzati
Carosati, Daniele
Italy
Armenzano Astronomical Observatory
Charlot, Patrick
France, Bordeaux
Université de Bordeaux
France, Paris
Cnrs Centre National de la Recherche Scientifique
Chen, Wenping
Taiwan, Taoyuan
National Central University
Dultziń-Hacyan, Deborah
Mexico, Mexico
Universidad Nacional Autónoma de México
Forné, E.
Unknown Affiliation
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
Heidt, Jochen
Germany, Heidelberg
Landessternwarte Heidelberg
Hiriart, David
Mexico, Mexico
Universidad Nacional Autónoma de México
Jelínek, Martin
Spain, Madrid
Consejo Superior de Investigaciones Científicas
Jorstad, Svetlana G.
United States, Boston
Boston University
Kimeridze, Givi N.
Georgia, Abastumani
Abastumani Astrophysical Observatory
Grishina, Tatiana S.
Russian Federation, Saint Petersburg
Saint Petersburg State University
Kopatskaya, Evgenia N.
Russian Federation, Saint Petersburg
Saint Petersburg State University
Kostov, Andon B.
Bulgaria, Sofia
The Bulgarian Academy of Sciences
Kurtanidze, Omar M.
Georgia, Abastumani
Abastumani Astrophysical Observatory
L¨ahteenm¨aki, Anne A.
Finland, Espoo
Aalto University
Lanteri, Luciano
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Larionova, Liudmilla V.
Russian Federation, Saint Petersburg
Saint Petersburg State University
Leto, Paolo
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
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
Lee, Chung-uk
South Korea, Daejeon
Korea Astronomy and Space Science Institute
Ligustri, Rolando
Unknown Affiliation
Lindfors, Elina J.
Finland, Turku
Turun Yliopisto
Marscher, Alan P.
United States, Boston
Boston University
Mihov, Boyko M.
Bulgaria, Sofia
The Bulgarian Academy of Sciences
Nikolashvili, M. G.
Georgia, Abastumani
Abastumani Astrophysical Observatory
Nikolov, Yanko M.
Bulgaria, Sofia
The Bulgarian Academy of Sciences
Bulgaria, Sofia
Sofia University St. Kliment Ohridski
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
Robb, Russell M.
Canada, Victoria
University of Victoria
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
Sigua, Lorand A.
Georgia, Abastumani
Abastumani Astrophysical Observatory
Smart, Richard L.
Italy, Rome
Istituto Nazionale Di Astrofisica, Rome
Takalo, Leo O.
Finland, Turku
Turun Yliopisto
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
Volvach, A. E.
Ukraine, Bakhchysarai
Crimean Astrophysical Observatory Ras
Statistics
Citations: 60
Authors: 65
Affiliations: 28
Identifiers
Doi:
10.1051/0004-6361/200912953
ISSN:
14320746
Research Areas
Cancer
Environmental