Author(s): Aharonian F., Berghaus P., Bussons Gordo J., Chounet L.-M., Degrange B., Djannati-Ataï A., Dubus G., Espigat P., Feinstein F., Fleury P., Fontaine G., Gallant Y., Giebels B., Lemière A., Lemoine-Goumard M., Leroy N., Martineau-Huynh O., Marcowith A., De Naurois M., Ouchrif M., Pita S., Punch M., Raux J., Redondo I., Rolland L., Tavernet J.-P., Terrier R., Théoret C.G., Tluczykont M., Vasileiadis G.
(Article) Published:
Astronomy & Astrophysics, vol. 439 p.1013-1021 (2005)
Links openAccess full text : 
Ref HAL: in2p3-00024344_v1
Ref Arxiv: astro-ph/0505219
DOI: 10.1051/0004-6361:20053195
Ref. & Cit.: NASA ADS
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Abstract:
The serendipitous discovery of an unidentified extended TeV $\gamma$-ray source close to the galactic plane named HESS J1303-631 at a significance of 21 standard deviations is reported. The observations were performed between February and June 2004 with the H.E.S.S. stereoscopic system of Cherenkov telescopes in Namibia. HESS J1303-631 was discovered roughly 0.6 \degres north of the binary system PSR B1259-63/SS 2883, the target object of the initial observation campaign which was also detected at TeV energies in the same field of view. HESS J1303-631 is extended with a width of an assumed intrinsic Gaussian emission profile of $\sigma$ = (0.16 $\pm$ 0.02)\degres and the integral flux above 380 GeV is compatible with constant emission over the entire observational period of (17$\pm$ 3)% of the Crab Nebula flux. The measured energy spectrum can be described by a power-law dN/dE $\sim$ E$^{-\Gamma}$ with a photon index of $\Gamma$ = 2.44 $\pm 0.05$_{stat} \pm$ 0.2$_{syst}$. Up to now, no counterpart at other wavelengths is identified. Various possible TeV production scenarios are discussed.