We present radio polarimetry results for nine Southern pulsars. Six of the nine are young, with characteristic ages less than 100 kyr and high spin-down luminosities. All six show significant linear polarization, and we confirm a previously noticed trend in which the degree of linear polarization increases with spin-down luminosity. We have used the rotating vector model to fit the observed position angle data for PSR J1513–5908 (B1509–58). We find that a magnetic inclination angle α > 60° is excluded at the 3σ level in the fit, and that the geometry suggested by the morphology of an apparent bipolar X-ray outflow is marginally inconsistent with a recent model of the pulsar magnetosphere.

Results from an analysis of polarization data, at three different frequencies, for PSR B1133+16, show a clear systematic phase shift between the mode separated profiles for the two orthogonal modes. It is found that the shift has opposite signs for the two components of the profile. Further, the shift shows a tendency to increase at lower frequencies. The implications of these results for the origin of orthogonal modes and the location of pulsar emission regions are discussed.

Polarization profiles of several hundred pulsars have been published recently (eg. Gould & Lyne 1998, GL98; Weisberg et al. 1999). In this report, we summarize the characteristics of circular and high linear polarizations of pulsar profiles, based on all previously published data.

Upon re-examining the characteristic polarization angle sweep of rotation-powered pulsars, we find that the sweep is perceptibly shifted by aberrational effects and by polar-cap current flow. In addition to the previously known phase shift of the entire sweep by ΔΦ = −4r/RL, aberration shifts the polarization angle itself by ΔΨ = −(10/3)(r/RL) cos α. Similarly, current flow above the polar cap shifts the polarization sweep by ΔΨ = (10/3)(r/RL)(J/JGJ) COS α, potentially providing a method of directly measuring the magnitude of the current. The competition between these two effects produces a potentially observable signature in the polarization angle sweep.

Multi-frequency, single-pulse polarimetric observations of the Vela pulsar have been made using the VLA. These high time resolution measurements allow us to probe the geometry, and the time dependent characteristics of the radio emission region. Evidence for multiple emission components with differing spectral indices is found.

Two modes of orthogonal polarization are generally observed in the radio emission from pulsars. Essentially all attempts to calculate the average profiles of the individual modes have assumed that the modes occur separately. We have presented evidence, however, that the modes occur simultaneously. Therefore, we believe that “mode-separated” pulse profiles which have been published to date reveal little about the polarization properties of the individual modes.

Calculating mode-separated pulse profiles for superposed orthogonal modes is complicated by the unknown polarization properties of the individual modes. However, the simplest model of pulsar radio emission which can explain the wide variety in the emission’s polarization is one in which the individual modes are completely polarized. We use our simple model to compute the average profiles of the orthogonal modes in PSR B0525+21. The total intensity of the two mode profiles resembles the overall pulse profile, and each profile is highly linearly polarized.

The evolution of the multipolar structure of the magnetic field of isolated neutron stars is studied assuming the currents to be confined to the crust. Lower orders (≤ 25) of multipole are seen to evolve in a manner similar to the dipole suggesting little or no evolution of the expected pulse shape. We also study the multifrequency polarization position angle traverse of PSR B0329+54 and find a significant frequency dependence above 2.7 GHz. We interpret this as an evidence of strong multipolar magnetic field present in the radio emission region.

Pulsar polarimetry is an important tool for the investigation of the physical processes and the environment in the magnetosphere. However, the great variety of observed polarization states and the few obvious systematics hamper a straightforward interpretation. In this paper it is shown that the polarimetric features of pulsars are much more systematic at high radio frequencies. An analysis of 116 profiles at 4.85 GHz reveals a clear correlation between the degree of polarization and Ė. Also evidence is shown for pulsars with a heavily increasing degree of circular polarization. Further, a basic concept of a simple magnetospheric propagation scenario is presented, which can account for a variety of polarimetric properties of pulsars.

We have studied the temporal behavior of linearly polarized position angle in a sample of 98 pulsars observed from Arecibo over a four–year period in a search for free precession and changes in interstellar magnetic fields along pulsar– earth lines of sight. We set upper limits on changes in position angle.

The pulsar PSR 1641-45 was observed using the S2 VLBI Recording System at 1.6 GHz with radio telescopes at Tidbinbilla and Narrabri in Australia, and at Hartebeesthoek in South Africa. The data were correlated with the Canadian S2 VLBI Correlator using the ‘fast-dumping’ mode in conjunction with two independent pulsar gates. The high time and spectral resolution capabilities of this correlator permit a detailed examination of dispersion and dispersion-removal effects on individual pulses, and a comparison of these effects from pulse to pulse over the duration of the observation. We give a brief summary of the pulsar processing capabilities highlighted by examples from the PSR 1641-45 data.

The WAPP is a new Pulsar Processor for Arecibo Observatory. Key features are wideband operation (100 MHz) and good time resolution (16 microseconds).

The Giant Metrewave Radio Telescope (GMRT) coming up near Pune, India will be one of the important instruments for pulsar research work at metre wavelengths. Here we describe the capabilities of the GMRT for pulsar work and give the current status of the telescope in this context. Results from recent test observations are also summarised.

PuMa is a fully digital PulsarMachine the operation at the Westerbork Synthesis Radio Telescope (WSRT). Its design is based on the use of Digital Signal Processors. It has two modes of operation: a baseband recording mode and a digital filterbank mode.

Coherent de-dispersion removes the dispersive effect of the interstellar medium by convolving the digitally sampled telescope output voltages with an inverse filter function, derived from the tenuous plasma dispersion law. The time resolution obtainable by this method is limited only by the bandwidth that can be sampled sufficiently fast as to avoid aliasing. This allows high time resolution, therefore high precision, timing and polarimetry observations of millisecond pulsars. We present here the first results from the Jodrell Bank coherent de-dispersion system.

The Caltech-Parkes-Swinburne Recorder (CPSR) was installed at the Parkes Radio-telescope in August of 1998. It is capable of continuously two-bit quadrature-sampling a 20 MHz bandpass in two polarizations, though other configurations are possible. Since its successful installation, over 17 Terabytes of observational data have been recorded. These data were processed using the Swinburne Baseband Processing System (SBPS), a suite of data management and reduction software executed using a Beowulf-style cluster of high-performance workstations. A description of CPSR and SBPS is presented herein, followed by a brief presentation of some results from the past year of observations, and an outline of possible future uses of the system.

In this paper we discuss an arithmetic method for mean pulse profile de-disperse. We proceed from the principle of dispersion measure, and invert the de-dispersion problem as to refutations of solving integral equations. Under idealization condition, the refutations results fit very well with the given theoretical curvature.

Although less than 1 % of all radio pulsars are detected at optical wavelengths, their optical emission can yield a wealth of information that is either very difficult or plainly impossible to obtain at other wavelengths.

The Cananea-Ljubljana Young Pulsar Optical Survey, or CLYPOS, is an observational study of ≳ 30 known radio pulsars, in search for pulsed optical emission. The survey is being carried out at the 2.12m telescope of the Observatorio Astrofísico Guillermo Haro, near Cananea, Sonora, using the stroboscopic camera of the University of Ljubljana. We restricted the study to young pulsars with declination δ > −35°, prioritized in terms of E/d2. Our strategy consists in spending two hours of observing time per pulsar, scanning the whole pulsed-phase interval three times. Further details are given below.

Using the high speed 2-d TRIFFID photometer, we have obtained phase resolved photometry of the Crab pulsar in UBV that allows us to flux the unpulsed light curve component. Following de-extinction, weighted least-square fitting indicates a power-law exponent of α = −0.62 ± 0.49. This is steeper than that reported for the peak components and its origin remains unclear with respect to contemporary magnetospheric theory.

PSR B0656+14’s high energy emission is consistent with that of combined magnetospheric and thermal (surface & polar cap) emission. Uncertainties with the radio-derived distance and X-ray instrumentation sensitivities complicate a definitive thermal characterisation however. A re-analysis of combined ROSAT/EUVE archival data in conjunction with integrated & phase-resolved optical photometry is shown to constrain this characterisation.