We present a detailed analysis of the gamma-ray emission from HESS J1745-303
with the data obtained by the Fermi Gamma-ray Space Telescope in the first ~29
months observation.The source can be clearly detected at the level of ~18-sigma
and ~6-sigma in 1-20 GeV and 10-20 GeV respectively. Different from the results
obtained by the Compton Gamma-ray Observatory, we do not find any evidence of
variability. Most of emission in 10-20 GeV is found to coincide with the region
C of HESS J1745-303. A simple power-law is sufficient to describe the GeV
spectrum with a photon index of ~2.6. The power-law spectrum inferred in the
GeV regime can be connected to that of a particular spatial component of HESS
J1745-303 in 1-10 TeV without any spectral break. These properties impose
independent constraints for understanding the nature of this "dark particle
accelerator".Comment: 8 pages, 3 figures, 1 table, accepted for publication in Ap
