Details

Autor(en) / Beteiligte

• Aharonian, F.
• Akhperjanian, A. G.
• Barres de Almeida, U.
• Bazer-Bachi, A. R.
• Becherini, Y.
• Behera, B.
• Bernlöhr, K.
• Bochow, A.
• Borrel, V.
• Brion, E.
• Brucker, J.
• Cheesebrough, A.
• Coignet, G.
• Costamante, L.
• Daniel, M. K.
• Degrange, B.
• Deil, C.
• Djannati-Ataï, A.
• Domainko, W.
• Drury, L. O'C.
• Dubois, F.
• Dubus, G.
• Dyrda, M.
• Egberts, K.
• Emmanoulopoulos, D.
• Espigat, P.
• Feinstein, F.
• Fiasson, A.
• Förster, A.
• Gabici, S.
• Gallant, Y. A.
• Gérard, L.
• Giebels, B.
• Glicenstein, J. F.
• Göhring, D.
• Heinz, S.
• Henri, G.
• Hoffmann, A.
• Hofmann, W.
• Horns, D.
• Jacholkowska, A.
• Jung, I.
• Katarzyński, K.
• Kaufmann, S.
• Kerschhaggl, M.
• Khangulyan, D.
• Kluźniak, W.
• Kneiske, T.
• Kosack, K.
• Lenain, J.-P.
• Martin, J. M.
• Marcowith, A.
• McComb, T. J. L.
• Naumann-Godo, M.
• Nekrassov, D.
• Niemiec, J.
• Nolan, S. J.
• Ohm, S.
• de Oña Wilhelmi, E.
• Orford, K. J.
• Ostrowski, M.
• Panter, M.
• Paz Arribas, M.
• Pedaletti, G.
• Pelletier, G.
• Pita, S.
• Pühlhofer, G.
• Punch, M.
• Quirrenbach, A.
• Raue, M.
• Rayner, S. M.
• Ripken, J.
• Rob, L.
• Rowell, G.
• Rudak, B.
• Ruppel, J.
• Sahakian, V.
• Schöck, F. M.
• Schröder, R.
• Schwanke, U.
• Schwarzburg, S.
• Schwemmer, S.
• Shalchi, A.
• Sikora, M.
• Skilton, J. L.
• Sol, H.
• Spangler, D.
• Stawarz, Ł.
• Steenkamp, R.
• Superina, G.
• Szostek, A.
• Tam, P. H.
• Tavernet, J.-P.
• Tibolla, O.
• Vasileiadis, G.
• Venter, C.
• Völk, H. J.
• Volpe, F.
• Ward, M.
• Zech, A.

Titel

Simultaneous multiwavelength observations of the second exceptional γ-ray flare of PKS 2155–304 in July 2006

Ist Teil von

• Astronomy and astrophysics (Berlin), 2009-08, Vol.502 (3), p.749-770

Ort / Verlag

Les Ulis: EDP Sciences

Erscheinungsjahr

2009

Quelle

Electronic Journals Library

Beschreibungen/Notizen

• Aims. The X-ray–TeV connection and the evolution of the emitting particle population is studied in high-energy peaked BL Lac objects, by obtaining spectral information in both bands on sub-hour timescales. Methods. Simultaneous observations with HESS, Chandra and the Bronberg optical observatory were performed on the BL Lac object PKS 2155–304 in the night of July 29–30 2006, when the source underwent a major γ-ray outburst during its high-activity state of Summer 2006. This event took place about 44 h after the other major outburst of the night of July 27–28, which is known for its ultrafast variability. An unprecedented 6 to 8 h of simultaneous, uninterrupted coverage was achieved, with spectra and light curves measured down to 7 and 2 min timescales, respectively. Results. The source exhibited one major flare along the night, at high energies. The γ-ray flux reached a maximum of ~11 times the Crab flux (>400 GeV), with rise/decay timescales of ~1 h, plus a few smaller-amplitude flares superimposed on the decaying phase. The emission in the X-ray and VHE γ-ray bands is strongly correlated, with no evidence of lags. The spectra also evolve with similar patterns, and are always soft (photon index Γ > 2), indicating no strong shift of the peaks in the spectral energy distribution towards higher energies. Only at the flare maximum is there evidence that the γ-ray peak is inside the observed passband, at ~400–600 GeV. The VHE spectrum shows a curvature that is variable with time and stronger at higher fluxes. The huge VHE variations (~22$\times$) are only accompanied by small-amplitude X-ray and optical variations (factor 2 and 15% respectively). The source has shown for the first time in a high-energy peaked BL Lac object a large Compton dominance $(L_{\rm C}/L_{\rm S}\sim 10)$ – rapidly evolving – and a cubic relation between VHE and X-ray flux variations, during a decaying phase. These results challenge the common scenarios for the TeV-blazar emission.