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Title: New constraints on the mid-IR EBL from the HESS discovery of VHE γ-rays from 1ES 0229+200
Authors: Aharonian, F.
Benbow, W.
Bernlöhr, K.
Bolz, O.
Borrel, V.
Braun, I.
Bühler, R.
Carrigan, S.
Clapson, A. C.
Costamante, L.
Domainko, W.
Hoffmann, A.
Hermann, G.
Nedbal, D.
Horns, D.
Kendziorra, E.
Santangelo, A.
Schwarzburg, S.
Martineau-Huynh, O.
Maurin, D.
De Naurois M
Bernlöhr, K.
Tavernet, J. -. P.
Rob, L.
Ruppel, J.
Schlickeiser, R.
Schröder, R.
Shalchi, A.
Steenkamp, R.
Martin, J. M.
Ostrowski, M.
Moderski, R.
Dickinson, H. J.
Rudak, B.
Zdziarski, A. A.
Hinton, J. A.
Rowell, G.
Katarzyński, K.
Brown, A. M.
Costamante, L.
Hofmann, W.
Sol, H.
Hoppe, S.
Zech, A.
Kosack, K.
Ohm, S.
Panter, M.
Renaud, M.
Van Eldik C
Volk, H. J.
Akhperjanian, A. G.
Chadwick, P. M.
Sahakian, V.
Hadjichristidis, C.
Dalton, M.
Bazer-Bachi, A. R.
Borrel, V.
Olive, J. -. P.
Beilicke, M.
Cornils, R.
Heinzelmann, G.
Raue, M.
Ripken, J.
Funk, S.
Füßling, M.
Kerschhaggl, M.
Lohse, T.
Schwanke, U.
Boisson, C.
Ranchón, S.
Lenain, J. -. P.
Brion, E.
Glicenstein, J. F.
Goret, P.
Moulin, E.
Rolland, L.
Vivier, M.
Punch, M.
De Barres Almeida U
Keogh, D.
Wagner, S. J.
Latham, I. J.
McComb, T. J. L.
Nolan, S. J.
Orford, K. J.
Osborne, J. L.
Schwemmer, S.
Rayner, S. M.
Spangler, D.
Terrier, R.
Ward, M.
Aharonian, F.
Büsching, I.
Holleran, M.
De Jager OC
Raubenheimer, B. C.
Venter, C.
Chounet, L. -. M.
Degrange, B.
Tam, P. H.
Fontaine, G.
Farnier, C.
Rosier-Lees, S.
Giebels, B.
Khelifi, B.
Lemoine-Goumard, M.
Superina, G.
Volpe, F.
Coignet, G.
Dubois, F.
Lamanna, G.
Vialle, J. P.
Djannati-Ataï, A.
Espigat, P.
Lemière, A.
Maurin, G.
De Oña Wilhelmi E
Vincent, P.
Pita, S.
O'C Drury L
Masterson, C.
Behera, B.
Emmanoulopoulos, D.
Hauser, M.
Pedaletti, G.
Stawarz, Ł.
Pühlhofer, G.
Feinstein, F.
Hauser, D.
Fiasson, A.
Gallant, Y. A.
Jacholkowska, A.
Komin, N.
Marcowith, A.
Egberts, K.
Vasileiadis, G.
Glück, B.
Bulik, T.
Jung, I.
Dyks, J.
Schöck, F.
Stegmann, C.
Boutelier, T.
Dubus, G.
Henri, G.
Pelletier, G.
Petrucci, P. -. O.
Förster, A.
First Published: Nov-2007
Publisher: EDP Sciences for European Southern Observatory (ESO)
Citation: Astronomy & Astrophysics, 2007, 475 (2)
Abstract: Aims.To investigate the very high energy (VHE: >100 GeV) $\gamma$-ray emission from the high-frequency peaked BL Lac 1ES 0229+200. Methods.Observations of 1ES 0229+200 at energies above 580 GeV were performed with the High Energy Stereoscopic System (HESS) in 2005 and 2006. Results.1ES 0229+200 is discovered by HESS to be an emitter of VHE photons. A signal is detected at the 6.6$\sigma$ level in the HESS observations (41.8 h live time). The integral flux above 580 GeV is $(9.4\pm1.5_{\rm stat}\pm1.9_{\rm syst}) \times 10^{-13}$ cm-2 s-1, corresponding to ~1.8% of the flux observed from the Crab Nebula. The data show no evidence for significant variability on any time scale. The observed spectrum is characterized by a hard power law ( $\Gamma = 2.50\pm0.19_{\rm stat}\pm0.10_{\rm syst}$) from 500 GeV to ~15 TeV. Conclusions.The high-energy range and hardness of the observed spectrum, coupled with the object's relatively large redshift ( z = 0.1396), enable the strongest constraints so far on the density of the Extragalactic Background Light (EBL) in the mid-infrared band. Assuming that the emitted spectrum is not harder than $\Gamma_{\rm int} \approx 1.5$, the HESS data support an EBL spectrum $\propto$ $\lambda^{-1}$ and density close to the lower limit from source counts measured by Spitzer, confirming the previous indications from the HEGRA data of 1ES 1426+428 (z=0.129). Irrespective of the EBL models used, the intrinsic spectrum of 1ES 0229+200 is hard, thus locating the high-energy peak of its spectral energy distribution above a few TeV.
DOI Link: 10.1051/0004-6361:20078462
ISSN: 0004-6361
eISSN: 1432-0746
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © 2007 ESO. Reproduced with permission from Astronomy & Astrophysics, © ESO.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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