The spikes are observed almost exclusively in a 10 degree phase window centred on the main pulse. Within that window the phase distribution has a periodic variation, producing a pattern reminiscent of the diffraction fringes associated with coherent emission from a finite aperture. We present timing observations of four millisecond pulsars, using data obtained over three years at the ATNF Parkes and NRAL Jodrell Bank radio telescopes. 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. We have imaged the fields of 35 pulsars with the VLA at 8.4 GHz to search for evidence that the pulsars have deposited energy into their surroundings in the form of an extended wind nebula.
Candidates have both a wide range of transverse velocities and rotational energy losses.
Point-like emission was detected toward 14 pulsars with peak flux densities between 0.2 and 3 mJy. After a careful examination of each source we conclude that these detections are simply the time-averaged pulsed flux density from the pulsars themselves and thus no new pulsar wind nebulae were discovered. In contrast, this fraction is two orders of magnitude larger for the six pulsars which are known unambiguously to have a radio pulsar wind nebula around them. Several explanations are given for this behavior and we conclude that only young pulsars with high rotational energy losses produce an observable radio nebula. These fluctuations are substantially above the predictions for interstellar scintillation at these high frequencies.