Showing papers by "W. van Straten published in 2001"

A test of general relativity from the three-dimensional orbital geometry of a binary pulsar

Abstract: Binary pulsars provide an excellent system for testing general relativity because of their intrinsic rotational stability and the precision with which radio observations can be used to determine their orbital dynamics. Measurements of the rate of orbital decay of two pulsars have been shown to be consistent with the emission of gravitational waves as predicted by general relativity, but independent verification was not possible. Such verification can in principle be obtained by determining the orbital inclination in a binary pulsar system using only classical geometrical constraints. This would permit a measurement of the expected retardation of the pulse signal arising from the general relativistic curvature of space-time in the vicinity of the companion object (the 'Shapiro delay'). Here we report high-precision radio observations of the binary millisecond pulsar PSR J0437-4715, which establish the three-dimensional structure of its orbit. We see the Shapiro delay predicted by general relativity, and we determine the mass of the neutron star and its white dwarf companion. The determination of such masses is necessary in order to understand the origin and evolution of neutron stars.

The Swinburne intermediate-latitude pulsar survey

Abstract: We have conducted a survey of intermediate Galactic latitudes using the 13-beam 21-cm multibeam receiver of the Parkes 64-m radio telescope. The survey covered the region enclosed by 5°<|b|<15° and −100°

A search for submillisecond pulsars

Abstract: We have conducted a search of 19 southern Galactic globular clusters for submillisecond pulsars at 660 MHz with the Parkes 64 m radio telescope. To minimize dispersion smearing we used the CPSR baseband recorder, which samples the 20 MHz observing band at the Nyquist rate. By possessing a complete description of the signal we could synthesize an optimal filter bank in software, and in the case of globular clusters of known dispersion measure, much of the dispersion could be removed using coherent techniques. This allowed for very high time resolution (25.6 μs in most cases), making our searches in general sensitive to submillisecond pulsars with flux densities greater than about 3 mJy at 50 cm. No new pulsars were discovered, placing important constraints on the proportion of pulsars with very short spin periods in these clusters.

A Search for Sub-Millisecond Pulsars

Abstract: We have conducted a search of 19 southern Galactic globular clusters for sub-millisecond pulsars at 660 MHz with the Parkes 64-m radio telescope. To minimize dispersion smearing we used the CPSR baseband recorder, which samples the 20 MHz observing band at the Nyquist rate. By possessing a complete description of the signal we could synthesize an optimal filterbank in software, and in the case of globular clusters of known dispersion measure, much of the dispersion could be removed using coherent techniques. This allowed for very high time resolution (25.6 us in most cases), making our searches in general sensitive to sub-millisecond pulsars with flux densities greater than about 3 mJy at 50 cm. No new pulsars were discovered, placing important constraints on the proportion of pulsars with very short spin periods in these clusters.

A test of general relativity from the three-dimensional orbital geometry of a binary pulsar

Abstract: Binary pulsars provide an excellent system for testing general relativity because of their intrinsic rotational stability and the precision with which radio observations can be used to determine their orbital dynamics. Measurements of the rate of orbital decay of two pulsars have been shown to be consistent with the emission of gravitational waves as predicted by general relativity, providing the most convincing evidence for the self-consistency of the theory to date. However, independent verification of the orbital geometry in these systems was not possible. Such verification may be obtained by determining the orientation of a binary pulsar system using only classical geometric constraints, permitting an independent prediction of general relativistic effects. Here we report high-precision timing of the nearby binary millisecond pulsar PSR J0437-4715, which establish the three-dimensional structure of its orbit. We see the expected retardation of the pulse signal arising from the curvature of space-time in the vicinity of the companion object (the `Shapiro delay'), and we determine the mass of the pulsar and its white dwarf companion. Such mass determinations contribute to our understanding of the origin and evolution of neutron stars.