We report on \gamma -ray analysis of the region containing the bright TeV source HESS J1640 - 465 and the close-by TeV source HESS J1641 - 463 using 64 months of observations with the Fermi Large Area Telescope ( LAT ) .
Previously only one GeV source was reported in this region and was associated with HESS J1640 - 465 .
With an increased dataset and the improved sensitivity afforded by the reprocessed data ( P7REP ) of the LAT , we now report the detection , morphological study and spectral analysis of two distinct sources above 100 MeV .
The softest emission in this region comes from the TeV source HESS J1641 - 463 which is well fitted with a power law of index \Gamma = 2.47 \pm 0.05 \pm 0.06 and presents no significant \gamma -ray signal above 10 GeV , which contrasts with its hard spectrum at TeV energies .
The Fermi -LAT spectrum of the second TeV source , HESS J1640 - 465 is well described by a power-law shape of index \Gamma = 1.99 \pm 0.04 \pm 0.07 that links up naturally with the spectral data points obtained by the High Energy Stereoscopic System ( H.E.S.S . ) .
These new results provide new constraints concerning the identification of these two puzzling \gamma -ray sources .