Very High Energy Gamma Rays from Isolated Radio Pulsars: A Survey

During the period 1985-1989 a group of 18 isolated radio pulsars (IRPs) was observed with the Nooitgedacht TeV gamma-ray telescope. Of the 18 IRPs observed only one (PSR 1509-58) gave a positive signal over an extended period (1985-1988). No evidence for pulsed emission was seen during the period between 1989 and 1991, however. Upper limits to the conversion efficiencies of spin-down power to TeV gamma-rays for steady pulsed emission for 17 of the IRPs were compared with the conversion efficiencies predicted from the outer magnetospheric gap model. This comparison indicated that post-Vela-like pulsars are not such good TeV (and hence also MeV to GeV) gamma-ray candidates, as predicted by the outer gap model.