Multifrequency Study of Giant Radio Pulses from the Crab Pulsar with the K5 VLBI Recording Terminal

TL;DR

This study presents simultaneous multifrequency observations of giant radio pulses from the Crab pulsar, revealing complex spectral modulation and unresolved burst structures, challenging existing emission models.

Contribution

It provides the first detailed multifrequency analysis of Crab pulsar GPs with high time resolution, showing spectral modulation and challenging the amplitude-modulated noise model.

Findings

Spectral modulation occurs on large and small frequency scales.

GP pulse shapes are composed of unresolved bursts correlated over 60 MHz.

Results challenge the amplitude-modulated noise model of pulsar emission.

Abstract

Simultaneous multifrequency observations of the Crab pulsar giant pulses (GPs) were performed with the 64-m Kalyazin radio telescope at four frequencies 0.6, 1.4, 2.2 and 8.3 GHz using the K5 VLBI recording terminal. The K5 terminal provided continuous recording in 16 4-MHz wide frequency channels distributed over 4 frequency bands. Several thousands of GPs were detected during about 6 hours of observations in two successive days in July 2005. Radio spectra of single GPs were analysed at separate frequencies and over whole frequency range. These spectra manifest notable modulation over frequency ranges, $\Delta\nu$, both on large ($\Delta\nu/\nu\approx 0.5$) and small ($\Delta\nu/\nu\approx 0.01$) frequency scales. Cross-correlation analysis of GPs at 2.2 GHz showed that their pulse shapes can be interpreted as an ensemble of unresolved bursts grouped together at time scales of $\approx 1$ mcs being well-correlated over a 60-MHz band. The corresponding GP cross-correlation functions do not obey the predictions of the amplitude-modulated noise model of Rickett (1975), thus indicating that unresolved components represent a small number of elementary emitters.