High-resolution single-pulse studies of the Vela Pulsar

Abstract

We present high-resolution multi-frequency single-pulse observations of the Vela pulsar, PSR B0833-45, aimed at studying micro-structure, phase-resolved intensity fluctuations and energy distributions at 1.41 and 2.30 GHz. We show that the micro-pulse width in pulsars has a period dependence. Like individual pulses, Vela's micro-pulses are highly elliptically polarized. There is a strong correlation between Stokes parameters V and I in the micro-structure. We show that the V/I distribution is Gaussian with a narrow width and that this width appears to be constant as a function of pulse phase. The phase-resolved intensity distributions of I are best fitted with log-normal statistics. Extra emission components, i.e.``bump'' and ``giant micro-pulses'', discovered by Johnston et al.(2001) are also present at 2.3 GHz. The bump component seems to be an extra component superposed on the main pulse profile but does not appear periodically. The giant micro-pulses are time-resolved and have significant jitter in their arrival times. Their flux density distribution is best fitted by a power-law, indicating a link between these features and ``classical'' giant pulses as observed for the Crab pulsar, (PSR B0531+21), PSR B1937+21 and PSR B1821-24. We find that Vela contains a mixture of emission properties representing both ``classical'' properties of radio pulsars (e.g. micro-structure, high degree of polarization, S-like position angle swing, orthogonal modes) and features which are most likely related to high-energy emission (e.g. extra profile components, giant micro-pulses). It hence represents an ideal test case to study the relationship between radio and high-energy emission in significant detail.