Open AccessFurther results from the timing of the millisecond pulsars in 47 Tucanae
Author(s) -
Freire P. C.,
Camilo F.,
Kramer M.,
Lorimer D. R.,
Lyne A. G.,
Manchester R. N.,
D'Amico N.
Publication year - 2003
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2003.06392.x
Subject(s) - physics , millisecond pulsar , globular cluster , pulsar , astrophysics , astronomy , pulsar planet , orbital period , radio telescope , binary pulsar , orbit (dynamics) , orbital elements , galaxy , stars , engineering , aerospace engineering
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 1.7 × 10 16 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: . This is probably due to spin–orbit coupling; this effect seems to be significantly smaller for PSR J0023−7203J.