Fast Radio Bursts

The High Time Resolution Universe (HTRU) survey, which uses the 64-metre Parkes radio telescope (aka the Dish), is conducting a comprehensive survey of the southern sky searching for both millisecond and regular pulsars,  rotating radio transients (or RRATs), and giant pulses. The HTRU team recently detected four Fast Radio Bursts (FRBs), which are intense bursts of radio radiation that lasting between one and four milliseconds.

The first FRB was discovered in 2007 by Duncan Lorimer and collaborators, following the analysis of six years of archival data from the Parkes telescope. Studying the data from the Pulsar Survey of the Small Magellanic Cloud, the team found a FRB detected by Parkes on 21st August 2001, named FRB 010724, that was subsequently termed the ‘Lorimer Burst’. The discovery had many within the scientific community questioning the accuracy of the data and the distant origin of the Lorimer Burst – what could cause such an intense, short-lived  burst of radiation outside of our galaxy? It must be an extreme astrophysical event involving huge amounts of either mass or energy, perhaps resulting from merging neutron stars or a supernova explosion.  But why had only one such event been discovered, despite a number of other surveys?

The recent discovery of four more FRBs with the HTRU survey has confirmed the existence of these enigmatic radio signals and supports the findings of Lorimer et al., specifically that FRB originate from cosmological distances.

Artist’s composite of the CSIRO’s 64m Parkes Radio Telescope, showing an extragalactic radio burst appearing briefly, far from the Milky Way’s disk. (Credit: CSIRO/Harvard/Swinburne Astronomy Productions)

The HTRU survey covers the southern sky and is separated into high-, mid- and low- Galactic latitudes. The four newly discovered FRBs – named FRB 110627, FRB 120127, FRB 110703, FRB 110220 – were detected in the high-latitude survey data, more than 400 above the Galactic plane. The cosmological redshifts of the FRBs were calculated to be between 0.5 to 1, or about 11 billion light years for the furthest FRB.  Their intense radiation, short duration and vast distance indicates that they must result from cataclysmic events that expel a tremendous amount of both energy and mass.  No gamma-ray, X-ray or optical events were found to be associated with the four FRBs.

Radio map of the entire sky (in Galactic coordinates) showing pulsars found in the High Time Resolution Universe Survey (HTRU) as black dots, and the four newly detected Fast Radio Bursts (FRBs) marked as red asterisks. (Credit: MPIfR / C. Ng)

The origin of FRBs is remains unknown. The HTRU survey data suggests that FRB’s are not from pulsars.  Other possible candidates for FRBs include magnetars (magnetic neutron star), merging neutron stars, rotating radio transients, and evaporating black holes. The findings, lead by University of Manchester PhD student Dan Thornton and including Swinburne astronomers Matthew Bailes, Willem van Straten, Ramesh Bhat, Ben Barsdell, Paul Coster and Andrew Jameson, were published in the July 2013 edition of Science.

The team are now trying to determine the origin of FRBs, as well as detect more of them with the Parkes telescope, the Molonglo telescope, the Murchison Widefield Array, the Lovell Telescope, and the Effelsberg 100-m telescope. As little is still known about the space between galaxies, it is hoped that in the future FRBs will be able to be used as beacons across the interstellar medium and shed some light upon our understanding of  the distribution of matter throughout the Universe.

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[Sheridan Lacey and Sarah Maddison]

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