Giant Crab pulses at low frequency: statistics, scattering, polarization

Abstract

We carried out observations of Crab giant pulses at frequency 112 MHz from 2005 till 2008 on the Large Phased Array of the Pushchino Radio Astronomy Observatory. The scattering of pulses observed in various series varies by a factor of 3: from 11 ms in November 2005 till 34 ms in September 2008. The cumulative probability distribution for the peak intensities of the giant pulses for each of these series shows that the distribution is stable and is a power law with a single slope (n = −2.3). This testifies to stability of the mechanism generating the giant pulses. The energy in the pulses is conserved; i.e., the increase in the pulse intensity is proportional to the decrease in the scattering. Refractive scintillations at low frequencies in measurements with large time separation lead to variations in the relative number of giant pulses exceeding a given amplitude, proportional to the ratio of the mean flux densities of the pulsar in the corresponding observational series. The maximum energy of the recorded giant pulses is 2.5×107 Jy μs. Analysis of the giant pulses observed at other frequencies shows that the frequency dependence of the maximum energy of the giant pulses in the range of 23 MHz–9 GHz is a power‐law with index −2.2±0.2. We measured the rotation measure using GP which is RM = (−47.5±0.4) rad/m2, and the degree of linear polarization for pulses with measured frequency modulation was 9%÷17% for November 2005.