A LOFAR radio search for single and periodic pulses from M31

TL;DR

This study used LOFAR to search for radio bursts from M31, aiming to understand extragalactic pulsar populations and their giant pulses, but found no persistent signals despite detecting candidate bursts.

Contribution

First LOFAR survey targeting M31 for radio bursts, providing constraints on extragalactic pulsar brightness and giant pulse emission.

Findings

No persistent signals detected from M31

Crab-like pulsars in M31 are less than ten times brighter than Crab

Giant pulse fluence distribution follows a power law with slope 3.04

Abstract

Bright, short radio bursts are emitted by sources at a large range of distances: from the nearby Crab pulsar to remote Fast Radio Bursts (FRBs). FRBs are likely to originate from distant neutron stars, but our knowledge of the radio pulsar population has been limited to the Galaxy and the Magellanic Clouds. In an attempt to increase our understanding of extragalactic pulsar populations, and its giant-pulse emission, we employed the low-frequency radio telescope LOFAR to search the Andromeda Galaxy (M31) for radio bursts emitted by young, Crab-like pulsars. For direct comparison we also present a LOFAR study on the low-frequency giant pulses from the Crab pulsar; their fluence distribution follows a power law with slope 3.04(3). A number of candidate signals were detected from M31 but none proved persistent. FRBs are sometimes thought of as Crab-like pulsars with exceedingly bright giant pulses -- given our sensitivity, we can rule out that M31 hosts pulsars more than an order of magnitude brighter than the Crab pulsar, assuming their pulse scattering follows that of the known FRBs.