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http://hdl.handle.net/20.500.12386/33028
Title: | WEBT multiwavelength monitoring and XMM-Newton observations of BL Lacertae in 2007-2008 | Authors: | RAITERI, Claudia Maria VILLATA, Massimo CAPETTI, Alessandro Aller, M.F. Bach, U. Calcidese, P. Gurwell, M.A. Larionov, V.M. Ohlert, J. Nilsson, K. Strigachev, A. Agudo, I. Aller, H.D. Bachev, R. Benítez, E. Berdyugin, A. Böttcher, M. BUEMI, CARLA SIMONA Buttiglione, S. Carosati, D. Charlot, P. Chen, W.P. Dultzin, D. Forné, E. Fuhrmann, L. Gómez, J.L. Gupta, A.C. Heidt, J. Hiriart, D. Hsiao, W.-S. Jelínek, M. Jorstad, S.G. Kimeridze, G.N. Konstantinova, T.S. Kopatskaya, E.N. Kostov, A. Kurtanidze, O.M. Lähteenmäki, A. LANTERI, Luciano Larionova, L.V. LETO, PAOLO Latev, G. Le Campion, J.-F. Lee, C.-U. Ligustri, R. Lindfors, E. Marscher, A.P. Mihov, B. Nikolashvili, M.G. Nikolov, Y. Ovcharov, E. Principe, D. Pursimo, T. Ragozzine, B. Robb, R.M. Ros, J.A. Sadun, A.C. Sagar, R. Semkov, E. Sigua, L.A. SMART, Richard Laurence Sorcia, M. Takalo, L.O. Tornikoski, M. TRIGILIO, CORRADO Uckert, K. UMANA, Grazia Maria Gloria Valcheva, A. Volvach, A. |
Issue Date: | 2009 | Journal: | ASTRONOMY & ASTROPHYSICS | Number: | 507 | Issue: | 2 | First Page: | 769 | Abstract: | In 2007-2008 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, to study its emission properties. 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. The X-ray spectra are well fitted by a power law with photon index of about 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 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 extremely variable. 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 greater than 20000 K and a luminosity greater than 6 x 10^44 erg/s. | URI: | http://hdl.handle.net/20.500.12386/33028 | URL: | https://www.aanda.org/articles/aa/full_html/2009/44/aa12953-09/aa12953-09.html http://www.scopus.com/inward/record.url?eid=2-s2.0-70450207356&partnerID=MN8TOARS |
ISSN: | 0004-6361 | DOI: | 10.1051/0004-6361/200912953 | Bibcode ADS: | 2009A&A...507..769R | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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aa12953-09.pdf | Pdf editoriale | 635.92 kB | Adobe PDF | View/Open |
0909.1701.pdf | arXiv | 1.41 MB | Adobe PDF | View/Open |
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