Volume 481, Number 3, April III 2008
|Page(s)||L103 - L107|
|Published online||04 March 2008|
Letter to the Editor
Discovery of VHE γ-rays from the high-frequency-peaked BL Lacertae object RGB J0152+017
Max-Planck-Institut für Kernphysik, Heidelberg, Germany
2 Dublin Institute for Advanced Studies, Dublin, Ireland
3 Yerevan Physics Institute, Yerevan, Armenia
4 University of Durham, Department of Physics, Durham, UK
5 Centre d'Étude Spatiale des Rayonnements, CNRS/UPS, Toulouse, France
6 Landessternwarte, Universität Heidelberg, Heidelberg, Germany
7 Universität Hamburg, Institut für Experimentalphysik, Hamburg, Germany
8 Institut für Physik, Humboldt-Universität zu Berlin, Berlin, Germany
9 LUTH, Observatoire de Paris, CNRS, Université Paris Diderot, Meudon, France e-mail: firstname.lastname@example.org
10 IRFU/DSM/CEA, CE Saclay, Gif-sur-Yvette, France
11 Universität Erlangen-Nürnberg, Physikalisches Institut, Erlangen, Germany
12 Nicolaus Copernicus Astronomical Center, Warsaw, Poland
13 Unit for Space Physics, North-West University, Potchefstroom, South Africa
14 Laboratoire d'Astrophysique de Grenoble, INSU/CNRS, Université Joseph Fourier, Grenoble, France
15 Laboratoire Leprince-Ringuet, École Polytechnique, CNRS/IN2P3, Palaiseau, France
16 Laboratoire d'Annecy-le-Vieux de Physique des Particules, CNRS/IN2P3, Annecy-le-Vieux, France
17 European Associated Laboratory for Gamma-Ray Astronomy, jointly supported by CNRS and MPG
18 Astroparticule et Cosmologie (APC), CNRS, Université Paris 7 Denis Diderot, Paris; UMR 7164 (CNRS, Université Paris 7, CEA, Observatoire de Paris), France
19 Laboratoire de Physique Théorique et Astroparticules, CNRS/IN2P3, Université Montpellier II, Montpellier, France
20 School of Physics & Astronomy, University of Leeds, Leeds, UK
21 Institut für Astronomie und Astrophysik, Universität Tübingen, Tübingen, Germany
22 Toruń Centre for Astronomy, Nicolaus Copernicus University, Toruń, Poland
23 LPNHE, Université Pierre et Marie Curie Paris 6, Université Denis Diderot Paris 7, CNRS/IN2P3, Paris, France
24 Institute of Particle and Nuclear Physics, Charles University, Prague, Czech Republic e-mail: email@example.com
25 Obserwatorium Astronomiczne, Uniwersytet Jagielloński, Kraków, Poland
26 School of Chemistry & Physics, University of Adelaide, Adelaide, Australia
27 Institut für Theoretische Physik, Lehrstuhl IV: Weltraum und Astrophysik, Ruhr-Universität Bochum, Bochum, Germany
28 University of Namibia, Windhoek, Namibia
Accepted: 26 February 2008
Aims. The BL Lac object RGB J0152+017 () was predicted to be a very high-energy (VHE; >100 GeV) γ-ray source, due to its high X-ray and radio fluxes. Our aim is to understand the radiative processes by investigating the observed emission and its production mechanism using the High Energy Stereoscopic System (HESS) experiment.
Methods. We report recent observations of the BL Lac source RGB J0152+017 made in late October and November 2007 with the HESS array consisting of four imaging atmospheric Cherenkov telescopes. Contemporaneous observations were made in X-rays by the Swift and RXTE satellites, in the optical band with the ATOM telescope, and in the radio band with the Nançay Radio Telescope.
Results. A signal of 173 γ-ray photons corresponding to a statistical significance of 6.6σ was found in the data. The energy spectrum of the source can be described by a powerlaw with a spectral index of . The integral flux above 300 GeV corresponds to ~2% of the flux of the Crab nebula. The source spectral energy distribution (SED) can be described using a two-component non-thermal synchrotron self-Compton (SSC) leptonic model, except in the optical band, which is dominated by a thermal host galaxy component. The parameters that are found are very close to those found in similar SSC studies in TeV blazars.
Conclusions. RGB J0152+017 is discovered as a source of VHE γ-rays by HESS The location of its synchrotron peak, as derived from the SED in Swift data, allows clear classification as a high-frequency-peaked BL Lac (HBL).
Key words: galaxies: BL Lacertae objects: individual: RGB J0152+017 / gamma rays: observations / galaxies: BL Lacertae objects: general / galaxies: active
© ESO, 2008
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