Timing the millisecond pulsars in 47 Tucanae

In the last 10 years 20 millisecond pulsars have been discovered in the globular cluster 47 Tucanae. Hitherto, only 3 of these had published timing solutions. Here we improve upon these 3 and present 12 new solutions. These measurements can be used to determine a variety of physical properties of the pulsars and of the cluster. The 15 pulsars have positions determined with typical uncertianties of only a few milliarcsec and they are all located within 1.2 arcmin of the cluster centre. We have also measured the proper motions of 5 of the pulsars, which are consistent with the proper motion of 47 Tuc based on Hipparcos data. The period derivatives measured for many of the pulsars are dominated by the dynamical effects of the cluster gravitational field, and are used to constrain the surface mass density of the cluster. All pulsars have characteristic ages T > 170 Myr and magnetic fields B < 2.4e9 Gauss, and the average T > 1 Gyr. We have measured the rate of advance of periastron for the binary pulsar J0024-7204H, implying a total system mass 1.4+-0.8 solar masses.Comment: 17 pages, 11 included figures, accepted for publication in MNRA

The Parkes multibeam pulsar survey: IV. Discovery of 180 pulsars and parameters for 281 previously known pulsars

The Parkes multibeam pulsar survey has led to the discovery of more than 700 pulsars. In this paper, we provide timing solutions, flux densities and pulse profiles for 180 of these new discoveries. Two pulsars, PSRs J1736-2843 and J1847-0130 have rotational periods P > 6s and are therefore among the slowest rotating radio pulsars known. Conversely, with P = 1.8ms, PSR J1843-1113 has the third shortest period of pulsars currently known. This pulsar and PSR J1905+0400 (P = 3.8ms) are both solitary. We also provide orbital parameters for a new binary system, PSR J1420-5625, which has P = 34ms, an orbital period of 40 days and a minimum companion mass of 0.4 solar masses. The 10 degree-wide strip along the Galactic plane that was surveyed is known to contain 264 radio pulsars that were discovered prior to the multibeam pulsar survey. We have redetected almost all of these pulsars and provide new dispersion measure values and flux densities at 20cm for the redetected pulsars.Comment: 35 pages, accepted for publication in MNRAS, a high quality image of the figure on page 32 is available from http://www.atnf.csiro.au/research/pulsar/images/pmsurvey_fig.p

Observations of 20 millisecond pulsars in 47 Tucanae at 20 cm

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 20-cm wavelength. We detected all 11 previously known pulsars, and have discovered nine others, all of which are millisecond pulsars in binary systems. We have searched the data for relatively short orbital period systems, and found one pulsar with an orbital period of 96 min, the shortest of any known radio pulsar. The increased rate of detections with the new system resulted in improved estimates of the flux density of the previously known pulsars, determination of the orbital parameters of one of them, and a coherent timing solution for another one. Five of the pulsars now known in 47 Tucanae have orbital periods of a few hours and implied companion masses of only ~ 0.03 Msun. Two of these are eclipsed at some orbital phases, while three are seen at all phases at 20 cm but not always at lower frequencies. Four and possibly six of the other binary systems have longer orbital periods and companion masses ~ 0.2 Msun, with at least two of them having relatively large orbital eccentricities. All 20 pulsars have rotation periods in the range 2-8 ms.Comment: 15 pages, 6 embedded EPS figures, to be published in The Astrophysical Journa

Discovery of short-period binary millisecond pulsars in four globular clusters

We report the discovery using the Parkes radio telescope of binary millisecond pulsars in four clusters for which no associated pulsars were previously known. The four pulsars have pulse periods lying between 3 and 6 ms. All are in circular orbits with low-mass companions and have orbital periods of a few days or less. One is in a 1.7-hour orbit with a companion of planetary mass. Another is eclipsed by a wind from its companion for 40% of the binary period despite being in a relatively wide orbit. These discoveries result from the use of improved technologies and prove that many millisecond pulsars remain to be found in globular clusters.Comment: 4 pages, 2 figs, 1 table - Accepted by Astrophysical Journal Letter

Discovery of Two High-Magnetic-Field Radio Pulsars

We report the discovery of two young isolated radio pulsars with very high inferred magnetic fields. PSR J1119-6127 has period P = 0.407 s, and the largest period derivative known among radio pulsars, Pdot = 4.0e-12. Under standard assumptions these parameters imply a characteristic spin-down age of only tau = 1.6 kyr and a surface dipole magnetic field strength of B = 4.1e13 G. We have measured a stationary period-second-derivative for this pulsar, resulting in a braking index of n = 2.91+-0.05. We have also observed a glitch in the rotation of the pulsar, with fractional period change Delta_P/P = -4.4e-9. Archival radio imaging data suggest the presence of a previously uncataloged supernova remnant centered on the pulsar. The second pulsar, PSR J1814-1744, has P = 3.975 s and Pdot = 7.4e-13. These parameters imply tau = 85 kyr, and B = 5.5e13 G, the largest of any known radio pulsar. Both PSR J1119-6127 and PSR J1814-1744 show apparently normal radio emission in a regime of magnetic field strength where some models predict that no emission should occur. Also, PSR J1814-1744 has spin parameters similar to the anomalous X-ray pulsar (AXP) 1E 2259+586, but shows no discernible X-ray emission. If AXPs are isolated, high magnetic field neutron stars (``magnetars''), these results suggest that their unusual attributes are unlikely to be merely a consequence of their very high inferred magnetic fields.Comment: 7 pages, 3 embedded EPS figures, to be published in Ap