Sterile neutrinos in neutrinoless double beta decay

We study possible contribution of the Majorana neutrino mass eigenstate $ u_h$ dominated by a sterile neutrino component to neutrinoless double beta ($0 ubetabeta$) decay. From the current experimental lower bound on the $0 ubetabeta$-decay half-life of $^{76}$Ge we derive stringent constraints on the $ u_h- u_e$ mixing in a wide region of the values of $ u_h$ mass. We discuss cosmological and astrophysical status of $ u_h$ in this mass region.