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A new radio luminosity equation for pulsars is presented which is based on the geometry of a polarcap model. Statistical results show that the emission component intensity distribution is Gaussian. There are 100 pulsars with new radio luminosity values. We show that the radio luminosity can be described by one relation L ∝ (BP2)1.07 or L ∝ Q'–1.4, Q' = 2P1.1Ṗ–15–0.4 over the whole range of period and period derivatives, contrary to other recently suggested luminosity laws.
We present the results of mean pulse polarization observations at 1560 MHz of 8 pulsars with high southern latitude, large values of dispersion measure, short period and low flux density. All of these pulsars have strong linear polarization with a mean value of 47% and no previously published polarization data.
While millisecond pulsars have very different period parameters and a different evolutionary history compared to “normal” pulsars, the properties of their pulsed emission are remarkably similar to those of normal pulsars.
PSR B1828–11 is a young pulsar once thought to be undergoing free precession and recently found instead to be switching magnetospheric states in tandem with spin-down changes. Here we show the two extreme states of the mode-changing found for this pulsar and comment briefly on its interpretation.
Multi-decade observing campaigns of the globular clusters 47 Tucanae and M15 have led to an outstanding number of discoveries. Here, we report on the latest results of the long-term observations of the pulsars in these two clusters. For most of the pulsars in 47 Tucanae we have measured, among other things, their higher-order spin period derivatives, which have in turn provided stringent constraints on the physical parameters of the cluster, such as its distance and gravitational potential. For M15, we have studied the relativistic spin precession effect in PSR B2127+11C. We have used full-Stokes observations to model the precession effect, and to constrain the system geometry. We find that the visible beam of the pulsar is swiftly moving away from our line of sight and may very soon become undetectable. On the other hand, we expect to see the opposite emission beam sometime between 2041 and 2053.
The first known pulsar glitch was discovered in the Vela pulsar at both Parkes and Goldstone in March 1969. Since then the number of known glitches has grown enormously, with more than 520 glitches now known in more than 180 pulsars. Details of glitch parameters and post-glitch recoveries are described and some implications for the physics of neutron stars are discussed.
The southern galactic-plane region, in the ranges 294° ≤ 1 ≤ 358°, −0°.075 ≤ b ≤ 0°.075, has been surveyed in the J = 1–0 line of 12CO with a sampling interval of 3′ arc. Observations were made with the 4-metre telescope at the CSIRO Division of Radiophysics in 1980 and 1981. Details of equipment and observing procedure are given in Robinson et al. (1982, 1983); see also McCutcheon et al. (1983).
It is widely accepted and almost certainly true that both pulsars and supernova remnants (SNRs) are products of the collapse of a star at the end of its evolution. Given this, it is a considerable puzzle why, of the more than 120 known SNRs in the Galaxy, only two have unambiguously associated pulsars. Beaming of the pulsar emission probably accounts for the absence of detectable pulsars in up to 80% of the SNRs; however, this still leaves 20–30 SNRs in which one should be able to detect a pulsar. Vivekanand and Narayan (1981) show that there is a deficit of pulsars with periods ≲0.5 s and suggest that a majority of pulsars do not become active for a time ∼104 years after their birth. This would account for the lack of pulsar-SNR associations. It is however possible that the observed lack of short-period pulsars is simply due to observational selection. In the past, most pulsar searches have been made at relatively low radio frequencies, typically close to 400 MHz. At these frequencies SNRs are bright and the effects of interstellar scattering are significant, especially for distant, short-period pulsars. Further, most of these searches have used a relatively long sampling interval, typically about 20 ms, which further reduces the sensitivity for short-period pulsars.
The galactic radio source G320.4–1.2 (MSH15–52) consists of several components, the most prominent of which is situated in the north-west quadrant and is associated with the Hα nebula RCW89. Caswell et al. (1981) mapped the source at 1.4 GHz with a resolution of 50″ arc and concluded that it was a single supernova remnant with all components having spectral index α ≈ −0.34. This SNR has become more significant with the recent discovery (Seward and Harnden, 1982) of an X-ray pulsar of period 150 ms at the position (1950) R.A. 15h09m59s.5, Dec. −58°56′57″ near the centre of the remnant and the detection of this pulsar at radio frequencies (Manchester et al., 1982). The pulsar has some similarities to the Crab pulsar in that its period derivative is extremely high and hence its characteristic age low, ∼1570 years, comparable to that of the Crab pulsar. Timing observations (Manchester and Durdin, unpublished) indicate that the pulsar is not a member of a binary system and hence that the pulsed X-ray emission is powered by rotational energy, as in the Crab pulsar.
A prompt radio burst has been observed from the supernova 1987a in the Large Magellanic Cloud. Observations were made at 0.843, 1.415, 2.29, and 8.41 GHz. At frequencies around 1 GHz, the peak flux density reached about 150 mJy and occurred within four days of the supernova. This event may be a weak precursor to a major radio outburst of the type previously observed in other extragalactic supernovae. Radio monitoring of the supernova is continuing at each of the above frequencies, and coordination is underway of a southern hemisphere VLBI array to map the radio outburst region as it expands. Differential astrometry carried out on prime-focus plates taken with the Anglo-Australian telescope indicates that the component, star 1, of Sanduleak's star SK-69202 is within 0.05 ± 0.13 arcsec of the supernova.
A reassessment of the taxonomic relationships of North American gigantopterids is presented in light of an examination of large populations of specimens housed in the US National Museum of Natural History. Variations in venation and subtle aspects of leaf shape facilitate refined understanding of the relationships and diversity of the North American gigantopterid species leading to an improved understanding of the taxonomic and biogeographic relationships of this group, which are found most abundantly in western equatorial Pangea and Cathaysia. Current literature suggests that there are eight North American genera, however, this study has revealed a morphological overlap of several previously defined genera, leading to the conclusion that Gigantopteridium encompasses the species previously treated as Cathaysiopteris yochelsonii as well as a new species, Gigantopteridium utebaturianum. The transfer of C. yochelsonii to Gigantopteridium yochelsonii suggests that Cathaysiopteris may represent a genus endemic to Cathaysia, limiting the biogeographical connection between the regions to Zeilleropteris, Gigantopteridium, Euparyphoselis, and Gigantonoclea.
During April, 1970, the 300-ft telescope of the National Radio Astronomy Observatory was used to determine the mean polarisation of the Crab Nebula pulsar radiation at several frequencies around 400 MHz. The position angle of the highly polarised precursor measured at each frequency, corrected for ionospheric Faraday rotation and plotted against inverse frequency squared is shown in Figure 1. The observed variation of the position angle with frequency is consistent with Faraday rotation of the plane of polarisation with a rotation measure of −40.5 ± 4.5 rad/m2. This value is of the same sign but larger than the rotation measure for the nebular radiation in the vicinity of the pulsar.
It has been suggested that for the Crab pulsar the radio radiation mechanism may be different from that in other pulsars. The principal observations leading to this suggestion are, firstly, the essentially constant position angle of the highly linearly polarised precursor, and secondly, the occasional large increases in intensity of the main pulse.
Pulsars are among the most highly polarized sources in the universe. The NVSS has cataloged 2 million radio sources with linear polarization measurements, from which we have selected 253 sources, with polarization percentage greater than 25%, as targets for pulsar searches. We believe that such a sample is not biased by selection effects against ultra-short spin or orbit periods. Using the Parkes 64-m telescope, we conducted searches with sample intervals of 50 μs and 80 μs, sensitive to submillisecond pulsars. Unfortunately we did not find any new pulsars.
Observations of the LMC SNR 0540-693 using the Australia Telescope Compact Array at a wavelength of 6cm show that the remnant consists of a central core coincident with the associated pulsar and a partial ring of about 65 arcsec diameter.
The number of known pulsars has significantly increased over the past few years. We have searched the literature to find papers announcing the discovery of pulsars or giving improved parameters for them. Data from the papers have been entered into a new pulsar catalog that can be accessed via a web interface or from the command line (on Solaris or Linux machines). The user may request over 120 different parameters, select pulsars of interest, generate custom variables and choose between different ways of displaying or tabulating the datA. Full bibliographic references are available for all observed parameters.
PSRs J1847–0130 and J1718–37184 have inferred surface dipole magnetic fields greater than those of any other known pulsars and well above the “quantum critical field” above which some models predict radio emission should not occur. These fields are similar to those of the anomalous X-ray pulsars (AXPs), which growing evidence suggests are “magnetars”. The lack of AXP-like X-ray emission from these radio pulsars (and the non-detection of radio emission from the AXPs) creates new challenges for understanding pulsar emission physics and the relationship between these classes of apparently young neutron stars.