2010ApJ...725L.131P

Sterile neutrinos (or right-handed neutrinos) are a plausible warm dark matter candidate. We find that the excess of the intensity in the 8.7 keV line (at the energy of the Fe XXVI Lyγ line) in the spectrum of the Galactic center observed by Suzaku cannot be explained by standard ionization and recombination processes. We suggest that the origin of this excess is via decays of sterile neutrinos with a mass of 17.4 keV. The estimated value of the mixing angle sin²(2θ) = (4.4±2.2)x10^–12 lies in the allowed region of the mixing angle for a dark matter sterile neutrino with a mass of 17-18 keV.