The nature of the PSR J2051-0827 eclipses

In the three years following the discovery of PSR J2051-0827, we have obser ved a large number of eclipse traverses over a wide frequency range. These data show that the pulsar usually undergoes complete eclipse at frequencies below 1 GHz. At higher frequencies the pulsar is often detected throughout this low-frequency eclipse region with pulse times of arrival being signif icantly delayed relative to the best-fitting timing model. Variability in t he magnitude of the delay is clearly seen and occurs on time-scales shorter than the orbital period. Simultaneous dual frequency observations highligh t the difference in the eclipse behaviour for two widely separated frequenc ies. The low-frequency eclipses are accompanied by a significant decrease i n pulsed flux density, while the flux density variations during higher freq uency eclipses are not well defined. We consider a number of eclipse mechan isms and find that scattering and cyclotron absorption in the magnetosphere of the companion are consistent with the phenomena presented here.