Wide-Band Spectra of Giant Radio Pulses from the Crab Pulsar

TL;DR

This study presents wide-band spectral observations of giant radio pulses from the Crab pulsar across multiple frequencies, revealing spectral diversity, correlations with fluence, and implications for fast radio burst models.

Contribution

It provides the most wide-band samples of Crab pulsar giant radio pulses and analyzes their spectral properties and correlations, advancing understanding of their emission mechanisms.

Findings

Most GRP spectra follow single power laws from 0.3 to 2.2 GHz.

A significant number of GRPs have hard spectra with spectral index around -1.

More energetic GRPs tend to have softer spectra.

Abstract

We present the results of the simultaneous observation of the giant radio pulses (GRPs) from the Crab pulsar at 0.3, 1.6, 2.2, 6.7, and 8.4 GHz with four telescopes in Japan. We obtain 3194 and 272 GRPs occurring at the main pulse and the interpulse phases, respectively. A few GRPs detected at both 0.3 and 8.4 GHz are the most wide-band samples ever reported. In the frequency range from 0.3 to 2.2 GHz, we find that about 70\% or more of the GRP spectra are consistent with single power laws and the spectral indices of them are distributed from $-4$ to $-1$. We also find that a significant number of GRPs have such a hard spectral index (approximately $-1$) that the fluence at 0.3 GHz is below the detection limit ("dim-hard" GRPs). Stacking light curves of such dim-hard GRPs at 0.3 GHz, we detect consistent enhancement compared to the off-GRP light curve. Our samples show apparent correlations between the fluences and the spectral hardness, which indicates that more energetic GRPs tend to show softer spectra. Our comprehensive studies on the GRP spectra are useful materials to verify the GRP model of fast radio bursts in future observations.