MILLISECOND PULSAR SEARCHES Results and Future Prospects

We discuss results of various surveys for millisecond radio pulsars, and make some comments on possible properties of the underlying population. Results of the Arecibo surveys indicate a density of millisecond pulsars (250 deg 2) ?1 above a threshold level of 1 mJy for long-period pulsars. Parkes results are consistent with Arecibo's after scaling to account for Parkes' baseline sensitivity of 3 mJy. Working with a sample of 15 binary millisecond \\eld" pulsars, we nd a hint of a deecit of pulsars with \intermediate" orbital periods, 12 d < P b < 67 d, which we cannot account for by selection eeects. We note that after accounting for kinematic biasing eeects, the intrinsic \spindown" age of a substantial fraction (1=3) of all eld millisecond pulsars is likely larger than the age of the Galactic disk. Resolution of this apparent paradox has consequences for initial spin periods of millisecond pulsars, and mass accretion rates in the low mass X-ray binary phase of their evolution. We brieey discuss some technical details and consider aspects of new search eeorts now underway, as well as future prospects. We exclude from review directed searches of stellar globular clusters.