Please use this identifier to cite or link to this item: http://hdl.handle.net/2381/11127
Title: Multi-wavelength observations of PKS 2155-304 with HESS
Authors: Aharonian, F.
Akhperjanian, A. G.
Bazer-Bachi, A. R.
Beilicke, M.
Benbow, W.
Berge, D.
Bernlohr, K.
Boisson, C.
Bolz, O.
Borrel, V.
Braun, I.
Breitling, F.
Brown, A. M.
Chadwick, P. M.
Chounet, L. M.
Cornils, R.
Costamante, L.
Degrange, B.
Dickinson, H. J.
Djannati-Atai, A.
Drury, LO.
Dubus, G.
Emmanoulopoulos, D.
Espigat, P.
Feinstein, F.
Fontaine, G.
Fuchs, Y.
Funk, S.
Gallant, Y. A.
Giebels, B.
Gillessen, S.
Glicenstein, J. F.
Goret, P.
Hadjichristidis, C.
Hauser, M.
Heinzelmann, G.
Henri, G.
Hermann, G.
Hinton, J. A.
Hofmann, W.
Holleran, M.
Horns, D.
Jacholkowska, A.
de Jager O. C.
Khelifi, B.
Komin, N.
Konopelko, A.
Latham, I. J.
Le Gallou R.
Lemiere, A.
Lemoine-Goumard, M.
Leroy, N.
Lohse, T.
Martin, J. M.
Martineau-Huynh, O.
Marcowith, A.
Masterson, C.
McComb, T. J. L.
de Naurois M.
Nolan, S. J.
Noutsos, A.
Orford, K. J.
Osborne, J. L.
Ouchrif, M.
Panter, M.
Pelletier, G.
Pita, S.
Puhlhofer, G.
Punch, M.
Raubenheimer, B. C.
Raue, M.
Raux, J.
Rayner, S. M.
Reimer, A.
Reimer, O.
Ripken, J.
Rob, L.
Rolland, L.
Rowell, G.
Sahakian, V.
Sauge, L.
Schlenker, S.
Schlickeiser, R.
Schuster, C.
Schwanke, U.
Siewert, M.
Sol, H.
Spangler, D.
Steenkamp, R.
Stegmann, C.
Tavernet, J. P.
Terrier, R.
Theoret, C. G.
Tluczykont, M.
Vasileiadis, G.
Venter, C.
Vincent, P.
Volk, H. J.
Wagner, S. J.
First Published: Nov-2005
Publisher: EDP Sciences for European Southern Observatory (ESO)
Citation: Astronomy & Astrophysics, 2005, 442 (3), pp. 895-907
Abstract: The High Energy Stereoscopic System (HESS) has observed the high-frequency peaked BL Lac object PKS 2155-304 in 2003 between October 19 and November 26 in Very High Energy (VHE) $\gamma$-rays ( $E\geq 160\,\rm GeV$ for these observations). Observations were carried out simultaneously with the Proportional Counter Array (PCA) on board the Rossi X-ray Timing Explorer satellite (RXTE), the Robotic Optical Transient Search Experiment (ROTSE) and the Nançay decimetric radiotelescope (NRT). Intra-night variability is seen in the VHE band, the source being detected with a high significance on each night it was observed. Variability is also found in the X-ray and optical bands on kilosecond timescales, along with flux-dependent spectral changes in the X-rays. A transient X-ray event with a 1500 s timescale is detected, making this the fastest X-ray flare seen in this object. No correlation can be established between the X-ray and the $\gamma$-ray fluxes, or any of the other wavebands, over the small range of observed variability. The average HESS spectrum shows a very soft power law shape with a photon index of $3.37 \pm 0.07_{\rm stat} \pm 0.10_{\rm sys}$. The energy outputs in the 2- $10\,\rm keV$ and in the VHE $\gamma$-ray range are found to be similar, with the X-rays and the optical fluxes at a level comparable to some of the lowest historical measurements, indicating that PKS 2155-304 was in a low or quiescent state during the observations. Both a leptonic and a hadronic model are used to derive source parameters from these observations. These parameters are found to be sensitive to the model of Extragalactic Background Light (EBL) that attenuates the VHE signal at this source's redshift (z=0.117).
DOI Link: 10.1051/0004-6361:20053353
ISSN: 0004-6361
Links: http://hdl.handle.net/2381/11127
http://www.aanda.org/articles/aa/abs/2005/42/aa3353-05/aa3353-05.html
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © 2005 ESO. Reproduced with permission from Astronomy & Astrophysics, © ESO.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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