A two-minute burst of highly polarised radio emission originating from low Galactic latitude

TL;DR

This paper reports the discovery of a highly-polarised, long-duration radio burst from low Galactic latitude, resembling ultra-long period pulsars but with a duration over a hundred times longer, suggesting a potentially new class of Galactic radio transients.

Contribution

The discovery of a unique, long-duration, highly-polarised radio burst at low Galactic latitude, expanding the understanding of ultra-long period sources and their possible connection to pulsars.

Findings

The burst lasted over two minutes with ~200 mJy flux.

The burst's properties are similar to pulsars but with much longer duration.

ULP sources may have a strong Galactic latitude dependence.

Abstract

Several sources of repeating coherent bursts of radio emission with periods of many minutes have now been reported in the literature. These "ultra-long period" (ULP) sources have no clear multi-wavelength counterparts and challenge canonical pulsar emission models, leading to debate regarding their nature. In this work we report the discovery of a bright, highly-polarised burst of radio emission at low Galactic latitude as part of a wide-field survey for transient and variable radio sources. ASKAP\,J175534.9$-$252749.1 does not appear to repeat, with only a single intense two-minute $\sim$200-mJy burst detected from 60~hours of observations. The burst morphology and polarisation properties are comparable to those of classical pulsars but the duration is more than one hundred times longer, analogous to ULPs. Combined with the existing ULP population, this suggests that these sources have a strong Galactic latitude dependence and hints at an unexplored population of transient and variable radio sources in the thin disk of the Milky Way. The resemblance of this burst with both ULPs and pulsars calls for a unified coherent emission model for objects with spin periods from milliseconds to tens of minutes. However, whether or not these are all neutron stars or have the same underlying power source remains open for debate.