The Thousand-Pulsar-Array programme on MeerKAT III: Giant pulse characteristics of PSR J0540$-$6919

TL;DR

This study analyzes giant radio pulses from PSR J0540$-$6919 using MeerKAT, revealing their polarization, flux distribution, scattering properties, and potential links to Fast Radio Burst phenomena, with implications for pulsar emission mechanisms.

Contribution

First detailed characterization of giant pulses from PSR J0540$-$6919, including polarization, flux distribution, and narrow-band features, using the MeerKAT telescope.

Findings

Giant pulses follow a power-law flux distribution with index -2.75.

Detected pulses exhibit significant polarization variability and scattering at L-band frequencies.

Presence of narrow-band flux knots similar to Fast Radio Bursts, not caused by scintillation or plasma lensing.

Abstract

PSR J0540$-$6919 is the second-most energetic radio pulsar known and resides in the Large Magellanic Cloud. Like the Crab pulsar it is observed to emit giant radio pulses (GPs). We used the newly-commissioned PTUSE instrument on the MeerKAT radio telescope to search for GPs across three observations. In a total integration time of 5.7 hrs we detected 865 pulses above our 7$\sigma$ threshold. With full polarisation information for a subset of the data, we estimated the Faraday rotation measure, $\rm{RM}=-245.8 \pm 1.0$ rad m$^{-2}$ toward the pulsar. The brightest of these pulses is $\sim$ 60% linearly polarised but the pulse-to-pulse variability in the polarisation fraction is significant. We find that the cumulative GP flux distribution follows a power law distribution with index $-2.75 \pm 0.02$. Although the detected GPs make up only $\sim$ 10% of the mean flux, their average pulse shape is indistinguishable from the integrated pulse profile, and we postulate that there is no underlying emission. The pulses are scattered at L-band frequencies with the brightest pulse exhibiting a scattering time-scale of $\tau = 0.92 \pm 0.02$ ms at 1.2 GHz. We find several of the giants display very narrow-band "flux knots" similar to those seen in many Fast Radio Bursts, which we assert cannot be due to scintillation or plasma lensing. The GP time-of-arrival distribution is found to be Poissonian on all but the shortest time-scales where we find four GPs in six rotations, which if GPs are statistically independent is expected to occur in only 1 of 7000 observations equivalent to our data.