Observations of 20 millisecond pulsars in 47 Tucanae at 20 centimeters

We have used a new observing system on the Parkes radio telescope to carry out a series of pulsar observations of the globular cluster 47 Tucanae at 2 0 cm wavelength We detected all 11 previously known pulsars and have discov ered nine others, all of which are millisecond pulsars in binary systems. W e have searched the data for relatively short orbital period systems, and f ound one pulsar with an orbital period of 96 minutes, the shortest of any k nown radio pulsar. The increased rate of detections with the new system res ulted in improved estimates of the flux density of the previously known pul sars, determination of the orbital parameters of one of them, and a coheren t timing solution for another one. Five of the pulsars now known in 47 Tuca nae have orbital periods of a few hours and implied companion masses of onl y similar to 0.03 M.. Two of these are eclipsed at some orbital phases, whi le three are seen at all phases at 20 cm but not always at lower frequencie s. Four and possibly six of the other binary systems have longer orbital pe riods and companion masses similar to 0.2 M., with at least two of them hav ing relatively large orbital eccentricities. All 20 pulsars have rotation p eriods in the range 2-8 ms.