J. F. Bell

The Parkes multi-beam pulsar survey - I. Observing and data analysis systems, discovery and timing of 100 pulsars

limiting flux density of the survey is about 0.2 mJy. At shorter or longer periods or higher dispersions, the sensitivity is reduced. Timing observations are carried out for pulsars discovered in the survey for 12‐18 months after confirmation to obtain accurate positions, spin parameters, dispersion measures, pulse shapes and mean flux densities. The survey is proving to be extremely successful, with more than 600 pulsars discovered so far. We expect that, when complete, this one survey will come close to finding as many pulsars as all previous pulsar surveys put together. The newly discovered pulsars tend to be young, distant and of high radio luminosity. They will form a valuable sample for studies of pulsar emission properties, the Galactic distribution and evolution of pulsars, and as probes of interstellar medium properties. This paper reports the timing and pulse shape parameters for the first 100 pulsars timed at Parkes, including three pulsars with periods of less than 100 ms which are members of binary systems. These results are briefly compared with the parameters of the previously known population.

Discovery of two high-magnetic-field radio pulsars

We report the discovery of two young isolated radio pulsars with very high inferred magnetic —elds. PSR J1119(6127 has period P \ 0.407 s, and the largest period derivative known among radio pulsars, Under standard assumptions these parameters imply a characteristic spin-down age of P0 \ 4.0 ) 10~12. only

The Parkes Multibeam Pulsar Survey – III. Young pulsars and the discovery and timing of 200 pulsars

The Parkes Multibeam Pulsar Survey has unlocked vast areas of the Galactic plane, which were previously invisible to earlier low-frequency and less-sensitive surveys. The survey has discovered more than 600 new pulsars so far, including many that are young and exotic. In this paper we report the discovery of 200 pulsars for which we present positional and spin-down parameters, dispersion measures, flux densities and pulse profiles. A large number of these new pulsars are young and energetic, and we review possible associations of γ -ray sources with the sample of about 1300 pulsars for which timing solutions are known. Based on a statistical analysis, we estimate that about 19 ± 6 associations are genuine. The survey has also discovered 12 pulsars with spin properties similar to those of the Vela pulsar, nearly doubling the known population of such neutron stars. Studying the properties of all known ‘Vela-like’ pulsars, we find their radio luminosities to be similar to normal pulsars, implying that they are very inefficient radio sources. Finally, we review the use of the newly discovered pulsars as Galactic probes and discuss the implications of the new NE2001 Galactic electron density model for the determination of pulsar distances and luminosities.

The Parkes Multibeam Pulsar Survey – II. Discovery and timing of 120 pulsars

The Parkes Multibeam Pulsar Survey is a sensitive survey of a strip of the Galactic plane with |b| < 5 ◦ and 260 ◦ < l < 50 ◦ at 1374 MHz. Here we report the discovery of 120 new pulsars and subsequent timing observations, primarily using the 76-m Lovell radio telescope at Jodrell Bank. The main features of the sample of 370 published pulsars discovered during the multibeam survey are described. Furthermore, we highlight two pulsars: PSR J1734−3333, a young pulsar with the second highest surface magnetic field strength among the known radio pulsars, Bs = 5.4 × 10 13 G, and PSR J1830−1135, the second slowest radio pulsar known,

Discovery of a Young Radio Pulsar in a Relativistic Binary Orbit

We report on the discovery of PSR J1141-6545, a radio pulsar in an eccentric, relativistic 5 hr binary orbit. The pulsar shows no evidence of being recycled, having a pulse period P = 394 ms, a characteristic age τc = 1.4 × 106 yr, and an inferred surface magnetic dipole field strength B = 1.3 × 1012 G. From the mass function and measured rate of periastron advance, we determine the total mass in the system to be 2.300 ± 0.012 M☉, assuming that the periastron advance is purely relativistic. Under the same assumption we constrain the pulsars mass to be Mp ≤ 1.348 M☉, and the companions mass to be Mc > 0.968 M☉ (both with 99% confidence). Given the total system mass and the distribution of measured neutron star masses, the companion is probably a massive white dwarf that formed prior to the birth of the pulsar. Optical observations can test this hypothesis.

Discovery of Five Binary Radio Pulsars

We report on five binary pulsars discovered in the Parkes multibeam Galactic plane survey. All of the pulsars are old, with characteristic ages (1-11) × 109 yr, and have relatively small inferred magnetic fields, (5-90) × 108 G. The orbital periods range from 1.3 to 15 days. As a group these objects differ from the usual low-mass binary pulsars (LMBPs): their spin periods of 9-88 ms are relatively long; their companion masses, 0.2-1.1 M☉, are, in at least some cases, suggestive of CO or more massive white dwarfs; and some of the orbital eccentricities, 10-5 e 0.002, are unexpectedly large. We argue that these observed characteristics reflect binary evolution that is significantly different from that of LMBPs. We also note that intermediate-mass binary pulsars apparently have a smaller scale height than LMBPs.

Two Young Radio Pulsars Coincident with EGRET Sources

We report the discovery and follow-up timing observations of two young energetic radio pulsars. PSR J1420-6048 has a period P = 68 ms and period derivative = 83 × 10-15, implying a characteristic age τc = 13 kyr and a surface dipole magnetic field strength B = 2.4 × 1012 G. PSR J1837-0604 has P = 96 ms and = 45 × 10-15, implying τc = 34 kyr and B = 2.1 × 1012 G. The two objects have large spin-down luminosities, and, on the basis of an empirical comparison of their properties with those of other young radio pulsars, they are expected to be observable as pulsed γ-ray sources. In fact, they lie within the error circles of γ-ray sources detected by the EGRET instrument on the Gamma Ray Observatory. We show that the pulsars are plausibly associated with the EGRET sources.

PSR J1016–5857: A Young Radio Pulsar with Possible Supernova Remnant, X-Ray, and Gamma-Ray Associations

We report the discovery of a young and energetic pulsar in the Parkes multibeam survey of the Galactic plane. PSR J1016-5857 has a rotation period of 107 ms and period derivative of 8.0 × 10-14, implying a characteristic age of 21 kyr and spin-down luminosity of 2.6 × 1036 ergs s-1. The pulsar is located just outside, and possibly interacting with, the shell supernova remnant G284.3-1.8. Archival X-ray data show a source near the pulsar position that is consistent with emission from a pulsar wind nebula. The pulsar is also located inside the error box of the unidentified EGRET source 3EG J1013-5915, for which it represents a plausible counterpart.

The Temperature and Cooling Age of the White Dwarf Companion to the Millisecond Pulsar PSR B1855+09

We report on Keck and Hubble Space Telescope observations of the binary millisecond pulsar PSR B1855+09. We detect its white dwarf companion and measure mF555W=25.90+/-0.12 and mF814W=24.19+/-0.11 (Vega system). From the reddening-corrected color, (mF555W-mF814W&parr0;0=1.06+/-0.21, we infer a temperature Teff=4800+/-800 K. The white dwarf mass is known accurately from measurements of the Shapiro delay of the pulsar signal, MC=0.258+0.028-0.016 M middle dot in circle. Hence, given a cooling model, one can use the measured temperature to determine the cooling age. The main uncertainty in the cooling models for such low-mass white dwarfs is the amount of residual nuclear burning, which is set by the thickness of the hydrogen layer surrounding the helium core. From the properties of similar systems, it has been inferred that helium white dwarfs form with thick hydrogen layers, with mass greater, similar3x10-3 M middle dot in circle, which leads to significant additional heating. This is consistent with expectations from simple evolutionary models of the preceding binary evolution. For PSR B1855+09, though, such models lead to a cooling age of approximately 10 Gyr, which is twice the spin-down age of the pulsar. It could be that the spin-down age were incorrect, which would call the standard vacuum dipole braking model into question. For two other pulsar companions, however, ages well over 10 Gyr are inferred, indicating that the problem may lie with the cooling models. There is no age discrepancy for models in which the white dwarfs are formed with thinner hydrogen layers ( less, similar3x10-4 M middle dot in circle).

A Tighter Test of the Local Lorentz Invariance of Gravity Using PSR J2317+1439

Gravity being a long-range force, one might {\it a priori} expect the Universes 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