A multiwavelength view of the flaring state of PKS 2155-304 in 2006

• Autores: Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, G.; Medina, Maria Clementina; Terrier, R.; luczykont, M.; Tzioumis, A.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Venter, L.; Vialle, J. P; Viana, A.; Vincent, P.; Völk, H. J.; Wagner, S. J.; Volpe, F.; Vorster, M.; Vorobiov, S.; Ward, M.; Wierzcholska, A.; White, R.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H. S.; H.E.S.S. Collaboration
• Año de publicación: 2012
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Active galaxies; Radiation mechanisms; Gamma ray galaxies; BL Lacertae objects; Non-thermal mechanisms; PKS 2155-304 (objeto BL Lacertae)
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

Context. Multiwavelength (MWL) observations of the blazar PKS 2155-304 during two weeks in July and August 2006, the period when two exceptional flares at very high energies (VHE, E ≳ 100 GeV) occurred, provide a detailed picture of the evolution of its emission. The complete data set from this campaign is presented, including observations in VHE γ-rays (H.E.S.S.), X-rays (RXTE, Chandra, Swift XRT), optical (Swift UVOT, Bronberg, Watcher, ROTSE), and in the radio band (NRT, HartRAO, ATCA). Optical and radio light curves from 2004 to 2008 are compared to the available VHE data from this period, to put the 2006 campaign into the context of the long-term evolution of the source. Aims: The data set offers a close view of the evolution of the source on different time scales and yields new insights into the properties of the emission process. The predictions of synchrotron self-Compton (SSC) scenarios are compared to the MWL data, with the aim of describing the dominant features in the data down to the hour time scale. Methods: The spectral variability in the X-ray and VHE bands is explored and correlations between the integral fluxes at different wavelengths are evaluated. SSC modelling is used to interpret the general trends of the varying spectral energy distribution. Results: The X-ray and VHE γ-ray emission are correlated during the observed high state of the source, but show no direct connection with longer wavelengths. The long-term flux evolution in the optical and radio bands is found to be correlated and shows that the source reaches a high state at long wavelengths after the occurrence of the VHE flares. Spectral hardening is seen in the Swift XRT data. Conclusions: The nightly averaged high-energy spectra of the non-flaring nights can be reproduced by a stationary one-zone SSC model, with only small variations in the parameters. The spectral and flux evolution in the high-energy band during the night of the second VHE flare is modelled with multi-zone SSC models, which can provide relatively simple interpretations for the hour time-scale evolution of the high-energy emission, even for such a complex data set. For the first time in this type of source, a clear indication is found for a relation between high activity at high energies and a long-term increase in the low frequency fluxes.
Fil: Abramowski, A.. Universitat Hamburg; Alemania
Fil: Acero, F.. Universite Montpellier II; Francia
Fil: Aharonian, F.. Max Planck Institut für Kernphysik; Alemania
Fil: Akhperjanian, A. G.. National Academy of Sciences of the Republic of Armenia; Armenia
Fil: Anton, G.. Universität Erlangen Nürnberg; Alemania
Fil: Medina, Maria Clementina. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomia; Argentina. CEA Saclay; Francia
Fil: Terrier, R.. Université Paris Diderot - Paris 7; Francia
Fil: luczykont, M.. Universitat Hamburg; Alemania
Fil: Tzioumis, A.. Australia Telescope National Facility; Australia
Fil: Valerius, K.. Universität Erlangen Nürnberg; Alemania
Fil: van Eldik, C.. Max Planck Institut für Kernphysik; Alemania
Fil: Vasileiadis, G.. Universite Montpellier II; Francia
Fil: Venter, C.. North West University; Sudáfrica
Fil: Venter, L.. Yerevan Physics Institute; Armenia
Fil: Vialle, J. P. Université de Savoie; Francia
Fil: Viana, A.. University Of Durham; Reino Unido
Fil: Vincent, P.. Université Paris Diderot - Paris 7; Francia
Fil: Völk, H. J.. Max Planck Institut für Kernphysik; Alemania
Fil: Wagner, S. J.. Universität Heidelberg; Alemania
Fil: Volpe, F.. Max Planck Institut für Kernphysik; Alemania
Fil: Vorster, M.. North West University; Sudáfrica
Fil: Vorobiov, S.. Universite Montpellier II; Francia
Fil: Ward, M.. University Of Durham; Reino Unido
Fil: Wierzcholska, A.. Uniwersytet Jagielloński; Polonia
Fil: White, R.. University of Leicester; Reino Unido
Fil: Zacharias, M.. Ruhr-universität Bochum; Alemania
Fil: Zajczyk, A.. Universite Montpellier II; Francia
Fil: Zdziarski, A. A.. Nicolaus Copernicus Astronomical Center; Polonia
Fil: Zech, A.. Université Paris Diderot - Paris 7; Francia
Fil: Zechlin, H. S.. Universitat Hamburg; Alemania
Fil: H.E.S.S. Collaboration.