  Several extensions of the Standard Model contain right-handed (sterile)
neutrinos in the GeV-TeV mass range. Due to their mixing with the active
neutrinos, they may give rise to novel effects in cosmology, neutrino physics,
and collider searches. In addition, right-handed neutrinos can also appear as
final states from dark matter annihilations, with important implications for
dark matter indirect detection searches. In this paper, we use current data
from the Fermi Large Area Telescope (6-year observation of dwarf spheroidal
galaxies) and H.E.S.S. (10-year observation of the Galactic center) to
constrain the annihilation of dark matter into right-handed neutrinos. We
consider right-handed neutrino with masses between 10 GeV and 1 TeV, including
both two-body and three-body decays, to derive bounds on the dark matter
annihilation rate, $\langle \sigma v\rangle$, as a function of the dark matter
mass. Our results show, in particular, that the thermal dark matter
annihilation cross section, $3\times 10^{-26}\, {\rm cm^3 s^{-1}} $, into
right-handed neutrinos is excluded for dark matter masses smaller than $200$
GeV.
