2003MNRAS.340.1359F

We have been observing the millisecond pulsars in the globular cluster 47 Tucanae (47 Tuc) at the Parkes radio telescope since 1999 August with threefold higher time-resolution than hitherto possible. We present the results in this paper, including: improved 1400-MHz pulse profiles; one new timing solution, for PSR J0024-7204S, which imposes stringent constraints on the acceleration model for 47 Tucanae and implies a projected mass-to-light ratio >1.4 M_☉/L_☉at the centre of the cluster; refined estimates for the five previously determined proper motions; and newly determined proper motions for six pulsars. We have detected, for the first time, relative motions between the pulsars. We have detected a second period derivative for the pulsar in the PSR J0024-7204H binary system, which could indicate the presence of a third nearby object, and improved measurement of the rate of advance of periastron of this pulsar, which yields a total system mass of 1.61±0.04 M_☉. We also have determined upper limits for the masses of any hypothetical planets orbiting the pulsars in 47 Tuc. PSR J0023-7203J shows variations of dispersion measure (DM) as a function of orbital phase with a total column density at superior conjunction of about 1.7x10¹⁶ cm^–2, 10 times smaller than observed for a similar system in the Galaxy. We interpret the small value as being due to a smaller inclination of the orbit of PSR J0023-7203J. We find that the DM variation with orbital phase changes with time, and we detect material at more than 90° (in orbital phase) from the companion. PSR J0024-7204O also shows variations of DM with orbital phase, but these are restricted to phases near the eclipse. This binary system displays significant monotonic variation of its orbital period: {formmu3}. This is probably due to spin-orbit coupling; this effect seems to be significantly smaller for PSR J0023-7203J.