We present a detailed single pulse study of PSR B1055–52 based on observations at the Parkes radio telescope .
The radio emission is found to have a complex modulation dominated by a periodicity of \sim { 20 } times its rotational period P ( 0.197s ) , whose phase and strength depends on pulse longitude .
This periodicity exhibits a phase-locked delay of about 2.5 P between the main pulse ( MP ) and interpulse ( IP ) , presumed to be the opposite poles of the pulsar .
This delay corresponds to a light travel distance of many times the light cylinder radius .
More complex modulations are found within the MP on timescales down to about 9 P , and both these and the principal modulation vary strongly across the ( at least ) 7 components which the MP and IP exhibit .
The nature of the single pulse emission , which ranges from smooth and longitudinally extended to ‘ spiky ’ , is also component-dependent .
Despite these disparities , the total pulse intensity distributions at the MP and IP are virtually identical in shape , suggesting a common emission mechanism .
In an attempt to account for the complex modulations we examine a number of physical models , both intrinsic ( which presuppose the pulsar to be an isolated neutron star ) and extrinsic ( appealing to the presence of circumstellar material to modulate the emission ) .
Significant objections can be made to each model , so this pulsar ’ s behaviour patterns remain a crucial challenge to theorists .