On Single-pulse Energies of Some Bright Pulsars Observed at 1.7 GHz

Abstract

Abstract We present Arecibo observations of the bright pulsars B0301+19, B0525+21, B0540+23, B0611+22, and B0823+26 at 1.7 GHz with 100 MHz bandwidth. No giant pulses were found, except for B0823+26, where we recorded a giant interpulse with 230 times the average peak intensity. The postcursor in B0823+26 shows a symmetric double-peaked structure, indicating that it is frequency dependent. In all pulsars, for a given single-pulse peak intensity there is a range of equivalent widths up to a maximum, which becomes smaller the stronger the pulses are, thereby apparently limiting the energy output. Forming average profiles from pulses with certain equivalent widths leads to profiles with changing component characteristics and could allow exploring the magnetosphere at different heights, assuming a dipolar field geometry. We found that the normalized lag-1 autocorrelation coefficient for single-pulse energies can be over 0.5, indicating high correlations. From the first peak of the energy autocorrelation function a so-far-unobserved 15-period modulation is found for B0540+23, as well as a possible 10-period modulation for B0611+22. We also show that a fit of the Weibull distribution to the cumulative probability for the energies yields a better fit than the usual lognormal distribution. The cumulative probability distributions permit an estimate of the nulling fraction, which ranges from 0.6% for B0611+22 to 24% for B0525+21.