Observation of TeV gamma rays from the Fermi bright galactic sources with the Tibet air shower array

Abstract:

Using the Tibet-III air shower array, we search for TeV γ-rays from 27 potential Galactic sources in the early list of bright sources obtained by the Fermi Large Area Telescope at energies above 100 MeV. Among them, we observe seven sources instead of the expected 0.61 sources at a significance of 2σ or more excess. The chance probability from Poisson statistics would be estimated to be 3.8× 10− 6. If the excess distribution observed by the Tibet-III array has a density gradient toward the Galactic plane, the expected number of sources may be enhanced in chance association. Then, the chance probability rises slightly, to 1.2× 10− 5, based on a simple Monte Carlo simulation. These low chance probabilities clearly show that the Fermi bright Galactic sources have statistically significant correlations with TeV γ-ray excesses. We also find that all seven sources are associated with pulsars, and six of them are …

Año de publicación:

2009

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