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First detection of a VHE gamma-ray spectral maximum from a Cosmic source: H.E.S.S. discovery of the Vela X nebula

F. Aharonian A.G. Akhperjanian A.R. Bazer-Bachi M. Beilicke Wystan Benbow David Berge K. Bernlohr C. Boisson O. Bolz V. Borrel I. Braun F. Breitling A.M. Brown R. Buhler S. Carrigan P.M. Chadwick L.-M. Chounet 1 R. Cornils L. Costamante B. Degrange 1 H.J. Dickinson A. Djannati-Atai 2 L.O'C. Drury G. Dubus 1 K. Egberts D. Emmanoulopoulos P. Espigat 2 F. Feinstein 3 G. Fontaine 1 S. Funk Y. Gallant 3 B. Giebels 1 J.F. Glicenstein P. Goret C. Hadjichristidis D. Hauser M. Hauser G. Heinzelmann G. Henri G. Hermann J.A. Hinton W. Hofmann M. Holleran Dieter Horns A. Jacholkowska 3 O.C. de Jager B. Khelifi 1 S. Klages Nu. Komin A. Konopelko I.J. Latham R. Le Gallou A. Lemiere 2 M. Lemoine-Goumard 1 T. Lohse J.M. Martin O. Martineau-Huynh 3 A. Marcowith C. Masterson T.J.L. Mccomb M. de Naurois 3 D. Nedbal S.J. Nolan A. Noutsos K.J. Orford J.L. Osborne M. Ouchrif 3 M. Panter G. Pelletier 4 S. Pita 2 G. Puhlhofer M. Punch 2 B.C. Raubenheimer M. Raue S.M. Rayner A. Reimer O. Reimer J. Ripken L. Rob L. Rolland G. Rowell V. Sahakian L. Sauge 4 S. Schlenker R. Schlickeiser C. Schuster U. Schwanke M. Siewert H. Sol D. Spangler R. Steenkamp C. Stegmann G. Superina J.-P. Tavernet 3 R. Terrier 2 C.G. Theoret 2 M. Tluczykont 1 C. van Eldik G. Vasileiadis 3 C. Venter P. Vincent 3 H.J. Volk S.J. Wagner M. Ward
Abstract : The Vela supernova remnant (SNR) is a complex region containing a number of sources of non-thermal radiation. The inner section of this SNR, within 2 degrees of the pulsar PSR B0833-45, has been observed by the H.E.S.S. gamma-ray atmospheric Cherenkov detector in 2004 and 2005. A strong signal is seen from an extended region to the south of the pulsar, within an integration region of radius 0.8 deg. around the position (RA = 08h 35m 00s, dec = -45 deg. 36' J2000.0). The excess coincides with a region of hard X-ray emission seen by the ROSAT and ASCA satellites. The observed energy spectrum of the source between 550 GeV and 65 TeV is well fit by a power law function with photon index = 1.45 +/- 0.09(stat) +/- 0.2(sys) and an exponential cutoff at an energy of 13.8 +/- 2.3(stat) +/- 4.1(sys) TeV. The integral flux above 1 TeV is (1.28 +/- 0.17 (stat) +/- 0.38(sys)) x 10^{-11} cm^{-2} s^{-1}. This result is the first clear measurement of a peak in the spectral energy distribution from a VHE gamma-ray source, likely related to inverse Compton emission. A fit of an Inverse Compton model to the H.E.S.S. spectral energy distribution gives a total energy in non-thermal electrons of ~2 x 10^{45} erg between 5 TeV and 100 TeV, assuming a distance of 290 parsec to the pulsar. The best fit electron power law index is 2.0, with a spectral break at 67 TeV.
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Submitted on : Tuesday, August 14, 2007 - 10:00:36 AM
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F. Aharonian, A.G. Akhperjanian, A.R. Bazer-Bachi, M. Beilicke, Wystan Benbow, et al.. First detection of a VHE gamma-ray spectral maximum from a Cosmic source: H.E.S.S. discovery of the Vela X nebula. Astronomy and Astrophysics - A&A, EDP Sciences, 2006, 448, pp.L43-L47. ⟨10.1051/0004-6361:200600014⟩. ⟨in2p3-00025549⟩



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