  In this paper, we will discuss a specific case that the dark matter particles
annihilate into right-handed neutrinos. We calculate the predicted gamma-ray
excess from the galactic center and compare our results with the data from the
Fermi-LAT. An approximately 10-60 GeV right-handed neutrino with heavier dark
matter particle can perfectly explain the observed spectrum. The annihilation
cross section $\langle \sigma v \rangle$ falls within the range $0.5$-$4 \times
10^{-26} \text{ cm}^3/\text{s}$, which is roughly compatible with the WIMP
annihilation cross section.
