|Discovery of VHE gamma-rays from the high-frequency-peaked BL Lac object RGB J0152+017 |
Author(s): Aharonian F., Bazer-Bachi A.R., Boisson C., Borrel V., Brion E., Boutelier T., Chounet L.-M., Coignet G., Degrange B., Djannati-Ataï A., Dubus G., Espigat P., Farnier C., Feinstein F., Fiasson A., Fontaine G., Gallant Y., Giebels B., Glicenstein J.F., Goret P., Henri G., Jacholkowska Agnieszka, Khélifi B., Komin Nukri, Lamanna G., Lemière A., Lemoine-Goumard M., Marcowith A., Moulin Emmanuel, Vasileiadis G.
Ref HAL: in2p3-00263434_v1
Ref Arxiv: 0802.4021
Ref. & Cit.: NASA ADS
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Aims: The BL Lac object RGB J0152+017 (z=0.080) was predicted to be a very high-energy (VHE; > 100 GeV) gamma-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 (H.E.S.S.) experiment. Methods: We report recent observations of the BL Lac source RGB J0152+017 made in late October and November 2007 with the H.E.S.S. 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 Nancay Radio Telescope. Results: A signal of 173 gamma-ray photons corresponding to a statistical significance of 6.6 sigma was found in the data. The energy spectrum of the source can be described by a powerlaw with a spectral index of 2.95+/-0.36stat+/-0.20syst. 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 gamma-rays by H.E.S.S. The location of its synchrotron peak, as derived from the SED in Swift data, allows clearly classification it as a high-frequency-peaked BL Lac (HBL).
Comments: 6 pages, 2 figures; Accepted for publication in A&A on February 20, 2008