Limits on the radiative decay of neutrinos

Astronomical observations at the x-ray, optical, and radio frequencies are used to show that the lifetime of neutrinos for radiative decay divided by the rest mass, Τ0/mν, exceeds 1017 sec/eV. If one makes the further assumption that mν>10-3 eV, then Τ0>~1019 sec. If there are other competing decays of neutrinos, it is then shown that Γνe(νe→x+γ)/Γνe(total)<~10-15 and Γνμ(νμ→x+γ)/Γνμ(total)<~3×10-6