A fast radio burst associated with a Galactic magnetar

TL;DR

The paper reports the discovery of a fast radio burst from a Galactic magnetar, linking magnetars to extragalactic FRBs and suggesting they can produce such energetic bursts detectable across the universe.

Contribution

First detection of a millisecond radio burst from a Galactic magnetar, supporting magnetars as sources of extragalactic FRBs and informing emission models.

Findings

Detected a radio burst with fluence of 1.5 Mega-Jansky milliseconds.

Burst energy is 4,000 times greater than previous Galactic bursts.

Event is comparable in energy to the weakest known extragalactic FRBs.

Abstract

Since their discovery in 2007, much effort has been devoted to uncovering the sources of the extragalactic, millisecond-duration fast radio bursts (FRBs). A class of neutron star known as magnetars is a leading candidate source of FRBs. Magnetars have surface magnetic fields in excess of $10^{14}$ G, the decay of which powers a range of high-energy phenomena. Here we present the discovery of a millisecond-duration radio burst from the Galactic magnetar SGR 1935+2154, with a fluence of $1.5\pm 0.3$ Mega-Jansky milliseconds. This event, termed ST 200428A(=FRB 200428), was detected on 28 April 2020 by the STARE2 radio array in the 1281--1468\,MHz band. The isotropic-equivalent energy released in ST 200428A is $4\times10^{3}$ times greater than in any Galactic radio burst previously observed on similar timescales. ST 200428A is just 40 times less energetic than the weakest extragalactic FRB observed to date, and is arguably drawn from the same population as the observed FRB sample. The coincidence of ST 200428A with an X-ray burst favours emission models developed for FRBs that describe synchrotron masers or electromagnetic pulses powered by magnetar bursts and giant flares. The discovery of ST 200428A implies that active magnetars like SGR 1935+2154 can produce FRBs at extragalactic distances. The high volumetric rate of events like ST 200428A motivates dedicated searches for similar bursts from nearby galaxies.