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Astronomy and Astrophysics 498 (2009) L25-L28
Search for diffuse gamma rays from the Galactic anticentre region above 100 GeV with CELESTE
R.J. Britto1, A. Jacholkowska1, F. Piron1, E. Brion, J.B. Gordo1, G. Debiais2, B. Fabre2, J. Lavalle1, F. Münz3, E. Nuss1, R.C. Rannot, T. Reposeur4
CELESTE Collaboration(s)

Context. Located in the French Pyrenees, CELESTE was the first ground-based gamma-ray telescope with an energy threshold below 100 GeV. It acquired data from 1999 to 2004, and allowed flux measurements of the Crab nebula and the blazars Mrk 421 and Mrk 501. Aims. We search for Galactic diffuse gamma-ray emission, which is most significant around the Galactic plane, for b = [-5 degrees, + 5 degrees]. Methods. By using the significant data set available for the Crab nebula, we selected Crab OFF-source data at various Galactic latitudes, in order to analyse the diffuse emission. Selection criteria were applied to the sky position, atmospheric conditions, and detector stability. Results. We obtained 108 mn of data in the Galactic anticentre region, providing the first upper limits of around 100 GeV to the diffuse gamma-ray emission with atmospheric Cherenkov detectors. These limits are phi(UL)(int) (E > 140 GeV) = 9.4 x 10(-3) m(-2) s(-1) sr(-1) and phi(UL)(int) (E > 120 GeV) = 1.2 x 10(-2) m(-2) s(-1) sr(-1).
1 :  LPTA - Laboratoire de Physique Théorique et Astroparticules
2 :  LP2A - Laboratoire de Physique Appliquée et d'Automatique
3 :  APC - UMR 7164 - AstroParticule et Cosmologie
4 :  CENBG - Centre d'Etudes Nucléaires de Bordeaux Gradignan
Physique/Astrophysique/Phénomènes cosmiques de haute energie

Planète et Univers/Astrophysique/Phénomènes cosmiques de haute energie
gamma rays: observations – methods: data analysis – methods: statistical – radiation mechanisms: non-thermal