arXiv subjects
Publications and source records attributed to J. F. Bell.
The Parkes multibeam pulsar survey is a high-frequency, fast-sampled survey of the Galactic Plane, expected to discover at least 500 new pulsars. To date, over 200 pulsars have been found, including several young pulsars and at least one with a very high magnetic field. Seven of the new stars are in binary systems; this number includes one probable double-neutron-star system, and one pulsar with an extremely massive companion.
Young radio pulsars shed vast amounts of rotational energy, sometimes as high as 100,000 times the total energy loss rate from the sun. The wide range of phenomena resulting from this energy loss include: glitches, timing noise, jets, bow shocks, bullets and plerions and are be reviewed from an observational perspective. Past and proposed surveys for young radio pulsars are summarised along with pulsar birth velocities and associations with supernova remnants. There are now 4 radio pulsars with measured braking indices. The resulting constraints on the evolution of young radio pulsars are discussed in light of the presently observed population of pulsars. Observations at optical, X-ray and gamma ray energies which provide a unique opportunity to study the emission and magnetospheric processes are described briefly. The status of pulsar birth velocities and supernova remnant associations are summarised.
We present timing observations of four millisecond pulsars, using data obtained over three years at the ATNF Parkes and NRAL Jodrell Bank radio telescopes. Astrometric, spin, and binary parameters are updated, and substantially improved for three pulsars, PSRs J0613-0200, J1045-4509 and J1643-1224. We have measured the time variation of the projected semi-major axis of the PSR J0437-4715 orbit due to its proper motion, and use it to constrain the inclination of the orbit and the mass of the companion. Some evidence is found for changes in the dispersion measures of PSRs J1045-4509 and J1643-1224. Limits are placed on the existence of planetary mass companions, ruling out companions with masses and orbits similar to the terrestrial planets of the solar system for eight pulsars.
The motivation for radio pulsar timing and its basic principles are reviewed. Present and future radio timing techniques and hardware are summarised and compared. The array of present timing programmes and their scientific goals are collated and described. Recent results and future prospects are discussed, with emphasis on multi-wavelength techniques where appropriate. Timing of radio pulsars at other wavelengths is summarised along with the provision of contemporary ephemerides for timing and searches at other wavelengths.
The observational evidence for jets and phenomena arising from rotation powered radio pulsars is reviewed, including many recent and exciting discoveries at X-ray wavelengths. The well studied jets of the Crab pulsar are summarised, including recent results from the HST. The evolutionary links between the known binary radio pulsars and jets sources in X-ray binaries are discussed.
Gravity being a long-range force, one might {\it a priori} expect the Universe's global matter distribution to select a preferred rest frame for local gravitational physics. The phenomenology of preferred-frame effects, in the strong-gravitational field context of binary pulsars, is described by two parameters $\hatα_1$ and $\hatα_2$. These parameters vanish identically in general relativity, and reduce, in the weak-field limit, to the two parametrized post-Newtonian (PPN) parameters $α_1$ and $α_2$. We derive a limit of $|\hatα_1| < 1.7\times 10^{-4}$ (90\%~C.L.) using the very low eccentricity binary pulsar PSR J2317+1439, improving by a factor of 3 on previous limits.
We demonstrate how measuring orbital period derivatives can lead to more accurate distance estimates and transverse velocities for some nearby binary pulsars. In many cases this method will estimate distances more accurately than is possible by annual parallax, as the relative error decreases as t^-5/2. Unfortunately, distance uncertainties limit the degree to which nearby relativistic binary pulsars can be used for testing the general relativistic prediction of orbital period decay to a few percent. Nevertheless, the measured orbital period derivative of PSR B1534+12 agrees within the observational uncertainties with that predicted by general relativity if the proper-motion contribution is accounted for.
Some theories of gravity predict the existence of preferred-frame effects and violations of conservation of energy and momentum. General relativity predicts no such effects. In the parameterised post-Newtonian (PPN) formalism, the parameter, \al3 $\equiv 0$ if these effects do not exist. The period derivatives ($\dot{P}$) of millisecond pulsars (MSPs) are used to more tightly constrain these effects by showing that $|$\al3$|$ $< 5 \times 10^{-16}$.
We report on optical observations of the low-mass binary millisecond pulsar systems J0034-0534 and J2145-0750. A faint (I=23.5) object was found to be coincident with the timing position of PSR J2145-0750. While a galaxy or distant main-sequence star cannot be ruled out, its magnitude is consistent with an ancient white dwarf, as expected from evolutionary models. For PSR J0034-0534 no objects were detected to a limiting magnitude of R=25.0, suggesting that the white dwarf in this system is cold. Using white dwarf cooling models, the limit on the magnitude of the PSR J0034-0534 companion suggests that at birth the pulsar in this system may have rotated with a period as short as 0.6 ms. These observations provide further evidence that the magnetic fields of millisecond pulsars do not decay on time scales shorter than 1 Gyr.
Binary radio pulsars are superb tools for mapping binary orbits, because of the precision of the pulse timing method (Taylor and Weisberg 1989). To date, all orbital parameters for binary pulsars have been derived from observations of the pulsar alone. We present the first observations of the radial velocity variations due to the binary motion of a companion to a radio pulsar. Our results demonstrate that the companion to the Small Magellanic Cloud pulsar PSR J0045-7319 is the B1V star identified by Kaspi et al. (1994). The mass ratio of the system is 6.3 +/- 1.2, which, for a neutron star mass of 1.4 Mo, implies a mass of 8.8 +/- 1.8 Mo for the companion, consistent with the mass expected for a B1V star. The inclination angle for the binary system is therefore 44 +/- 5 degrees, and the projected rotational velocity of the companion is 113 +/- 10 km/s. The heliocentric radial velocity of the binary system is consistent with that of other stars and gas in the same region of the Small Magellanic Cloud.