Spectral Flattening of Crab Giant Pulses at Low Frequencies

The frequency dependence of normal pulsar radio emission is typically observed to be a power law, with some indications of a flattening or turnover at low frequencies (<~ 100 MHz). The spectrum of the Crab pulsar's giant pulse emission has not been examined as closely. We conducted simultaneous wideband observations of the Crab pulsar, with the Parkes radio telescope and the Murchison Widefield Array, to study the spectral behaviour of its giant pulses. Our analysis shows that the mean spectral index of Crab giant pulses flattens at low frequencies, from -2.6 +/- 0.5 between the Parkes bands, to -0.7 +/- 1.4 between the lowest MWA subbands.