Possible Evidence for a Radiatively Decaying Neutrino

We consider nonstandard electroweak models which are able to explain the observed steplike structure in the cosmic background radiation at $\lambda =1667\mathrm{}\pm 10$ Å as due to radiative decays of massive cosmic neutrinos. In the standard electroweak theory the corresponding radiative lifetime is several orders of magnitude longer than observed, because of the purely left-handed structure of the charged weak currents. We point out that in models which include also right-handed currents, the lifetime can naturally be short enough to account for the astrophysical observations.