We report on the likely detection of \gamma -ray emission from the supernova remnant ( SNR ) Kesteven 27 ( Kes 27 ) .
We analyze 5.7 yr Fermi Large Area Telescope data of the SNR region and find an unresolved source at a position consistent with the radio brightness peak and the X-ray knot of Kes 27 , which is located in the eastern region of the SNR and caused by the interaction with a nearby HI cloud .
The source ’ s emission is best fit with a power-law spectrum with a photon index of 2.5 \pm 0.1 and a > 0.2 GeV luminosity of 5.8 \times 10 ^ { 34 } erg s ^ { -1 } assuming a distance of 4.3 kpc , as derived from radio observations of the nearby HI cloud .
Comparing the properties of the source with that of other SNRs that are known to be interacting with nearby high-density clouds , we discuss the origin of the source ’ s emission .
The spectral energy distribution of the source can be described by a hadronic model that considers the interaction of energetic protons , escaping from the shock front of Kes 27 , with a high-density cloud .