Possibility of detecting heavy neutral fermions in the Galaxy

It is shown that heavy neutral fermions in the galactic halo could produce numerous detectable low-energy events in a ``thermal'' neutrino detector if the heavy-fermionndashnucleon vector coupling is comparable in strength to the vector weak interaction. The conditions under which a detectable event rate could arise for fermions with purely axial-vector couplings are also discussed. In a silicon detector heavy-fermion events would be concentrated at low energies, and could be distinguished from solar or supernova neutrino events, which are expected to have a flatter energy spectrum. A measurement of the energy spectrum of heavy-fermion events could lead to a determination of the fermion mass, subject to astrophysical uncertainties concerning the velocity distribution of halo particles.