Spectral flattening of Crab Giant Pulses

TL;DR

This study investigates the spectral behavior of Crab pulsar's giant pulses across a wide frequency range, revealing a flattening of the spectral index at low frequencies, which enhances understanding of pulsar emission mechanisms.

Contribution

The paper provides the first detailed analysis of the Crab pulsar's giant pulse spectrum at low frequencies, showing spectral flattening not previously well-characterized.

Findings

Spectral index flattens at low frequencies

Mean spectral index changes from -2.6 to -0.7

Spectral behavior differs from normal pulsar emission

Abstract

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 $-2.6\pm0.5$ between the Parkes bands, to $-0.7\pm1.4$ between the lowest MWA subbands.