aa3353-05.pdf (424.18 kB)
Download file

Multi-wavelength observations of PKS 2155-304 with HESS

Download (424.18 kB)
journal contribution
posted on 24.10.2012, 08:53 by F. Aharonian, A. G. Akhperjanian, A. R. Bazer-Bachi, M. Beilicke, W. Benbow, D. Berge, K. Bernlohr, C. Boisson, O. Bolz, V. Borrel, I. Braun, F. Breitling, A. M. Brown, P. M. Chadwick, L. M. Chounet, R. Cornils, L. Costamante, B. Degrange, H. J. Dickinson, A. Djannati-Atai, LO. Drury, G. Dubus, D. Emmanoulopoulos, P. Espigat, F. Feinstein, G. Fontaine, Y. Fuchs, S. Funk, Y. A. Gallant, B. Giebels, S. Gillessen, J. F. Glicenstein, P. Goret, C. Hadjichristidis, M. Hauser, G. Heinzelmann, G. Henri, G. Hermann, J. A. Hinton, W. Hofmann, M. Holleran, D. Horns, A. Jacholkowska, de Jager O. C., B. Khelifi, N. Komin, A. Konopelko, I. J. Latham, Le Gallou R., A. Lemiere, M. Lemoine-Goumard, N. Leroy, T. Lohse, J. M. Martin, O. Martineau-Huynh, A. Marcowith, C. Masterson, T. J. L. McComb, de Naurois M., S. J. Nolan, A. Noutsos, K. J. Orford, J. L. Osborne, M. Ouchrif, M. Panter, G. Pelletier, S. Pita, G. Puhlhofer, M. Punch, B. C. Raubenheimer, M. Raue, J. Raux, S. M. Rayner, A. Reimer, O. Reimer, J. Ripken, L. Rob, L. Rolland, G. Rowell, V. Sahakian, L. Sauge, S. Schlenker, R. Schlickeiser, C. Schuster, U. Schwanke, M. Siewert, H. Sol, D. Spangler, R. Steenkamp, C. Stegmann, J. P. Tavernet, R. Terrier, C. G. Theoret, M. Tluczykont, G. Vasileiadis, C. Venter, P. Vincent, H. J. Volk, S. J. Wagner
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).

History

Citation

Astronomy & Astrophysics, 2005, 442 (3), pp. 895-907

Version

VoR (Version of Record)

Published in

Astronomy & Astrophysics

Publisher

EDP Sciences for European Southern Observatory (ESO)

issn

0004-6361

Copyright date

2005

Available date

24/10/2012

Publisher version

http://www.aanda.org/articles/aa/abs/2005/42/aa3353-05/aa3353-05.html

Language

en