Issue |
A&A
Volume 470, Number 2, August I 2007
|
|
---|---|---|
Page(s) | 475 - 489 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20077057 | |
Published online | 16 May 2007 |
Detection of VHE gamma-ray emission from the distant blazar 1ES 1101-232 with HESS and broadband characterisation
1
Max-Planck-Institut für Kernphysik, PO Box 103980, 69029 Heidelberg, Germany
2
Yerevan Physics Institute, 2 Alikhanian Brothers St., 375036 Yerevan, Armenia
3
Centre d'Étude Spatiale des Rayonnements, CNRS/UPS, 9 av. du Colonel Roche, BP 4346, 31029 Toulouse Cedex 4, France
4
Universität Hamburg, Institut für Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg, Germany
5
Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany
6
LUTH, UMR 8102 du CNRS, Observatoire de Paris, Section de Meudon, 92195 Meudon Cedex, France
7
DAPNIA/DSM/CEA, CE Saclay, 91191 Gif-sur-Yvette, Cedex, France
8
University of Durham, Department of Physics, South Road, Durham DH1 3LE, UK
9
Unit for Space Physics, North-West University, Potchefstroom 2520, South Africa
10
Laboratoire d'Astrophysique de Grenoble, INSU/CNRS, Université Joseph Fourier, BP 53, 38041 Grenoble Cedex 9, France
11
Laboratoire Leprince-Ringuet, IN2P3/CNRS, École Polytechnique, 91128 Palaiseau, France
12
Laboratoire d'Annecy-le-Vieux de Physique des Particules, IN2P3/CNRS, 9 Chemin de Bellevue, BP 110, 74941 Annecy-le-Vieux Cedex, France
13
European Associated Laboratory for Gamma-Ray Astronomy, jointly supported by CNRS and MPG
14
APC, 11 place Marcelin Berthelot, 75231 Paris Cedex 05, France (UMR 7164 (CNRS, Université Paris VII, CEA, Observatoire de Paris))
15
Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin 2, Ireland
16
Landessternwarte, Universität Heidelberg, Königstuhl, 69117 Heidelberg, Germany e-mail: G.Puehlhofer@lsw.uni-heidelberg.de
17
Laboratoire de Physique Théorique et Astroparticules, IN2P3/CNRS, Université Montpellier II, CC 70, Place Eugène Bataillon, 34095 Montpellier Cedex 5, France
18
Universität Erlangen-Nürnberg, Physikalisches Institut, Erwin-Rommel-Str. 1, 91058 Erlangen, Germany
19
Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
20
Laboratoire de Physique Nucléaire et de Hautes Énergies, IN2P3/CNRS, Universités Paris VI & VII, 4 place Jussieu, 75252 Paris Cedex 5, France
21
Institute of Particle and Nuclear Physics, Charles University, V Holesovickach 2, 180 00 Prague 8, Czech Republic
22
Institut für Theoretische Physik, Lehrstuhl IV: Weltraum und Astrophysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
23
University of Namibia, Private Bag 13301, Windhoek, Namibia
Received:
4
January
2007
Accepted:
28
March
2007
Context.The blazar 1ES 1101-232 was observed with the High Energy Stereoscopic System (HESS) of Atmospheric Cherenkov Telescopes (ACT) in 2004 and 2005, for a live time of 43 h. VHE (E > 1011 eV) γ-rays were detected for the first time from this object.
Aims.VHE observations of blazars are used to investigate the inner parts of the blazar jets, and also to study the extragalactic background light (EBL) in the near-infrared band.
Methods.Observations in 2005 were conducted in a multiwavelength campaign, together with the RXTE satellite and optical observations. In 2004, simultaneous observations with XMM-Newton were obtained.
Results.1ES 1101-232 was detected with HESS with an excess of 649 photons, at a significance of 10σ. The measured VHE γ-ray flux amounts to
= (5.63 ± 0.89)
10-13
cm-2 s-1 TeV-1, above a spectral energy threshold of 225 GeV.
No significant variation of the VHE γ-ray flux on any time scale
was found. 1ES 1101-232 exhibits a very hard spectrum, and
at a redshift of z = 0.186, is the blazar with the highest confirmed redshift detected in VHE γ-rays so far.
Conclusions.The data allow the construction of truly simultaneous spectral energy distributions of the source, from the optical to the VHE band. Using an EBL model with = 14 nWm-2 sr-1 at 1.5
m as presented in Aharonian et al. (2006a) suggests an intrinsic VHE power output peak of the source at above 3 TeV.
Key words: gamma rays: observations / galaxies: active / BL Lacertae objects: individual: 1ES 1101-232
© ESO, 2007
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