Real-time detections of 5 Fast Radio Bursts

 

08/05/19 — Five new Fast Radio Bursts have been published today by the UTMOST project.

Fast Radio Bursts are mysterious sources of energetic emission at radio frequencies, thought to lie billions of light years from the Earth. They last for only a few milliseconds and represent one of astronomy’s biggest puzzles.

The study, led by Swinburne PhD student Wael Farah, uses the real-time FRB detection system he created for the project, to catch FRBs within seconds of their arrival at the telescope, so that  data can be captured at the highest time and frequency resolution.

 

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One of the FRBs has remarkable time and frequency structure — as seen below:

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The FRB shows three peaks separated by approximately two milliseconds, with very similar frequency structure from peak to peak — seen as horizontal striations in the plot. These structures are probably due to the effects of ionised gas in the Milky Way galaxy as the radio burst travels to the Earth.

The 5 new FRBs were collected over 344 days of observing at the Molonglo telescope in a dedicated campaign, searching for the real-time detection system. Over 130 known pulsars were also seen giving off a total of 250,000 pulses during the campaign.

The study allows the FRB rate — the number of FRBs that occur across the whole sky each day — to be compared with experiments finding FRBs at other radio wavelengths, at the Parkes Radio Telescope and ASKAP (The Australian Square Kilometer Array Pathfinder) telescopes.

UTMOST operates in the frequency range 820 to 850 MHz, whereas Parkes and ASKAP operate at 1400 MHz.

The study finds fewer FRBs at this frequency than simple scaling of the rate at 1400 MHz suggests. It may be that FRBs are intrinsically less energetic at these wavelengths, and is a new clue to the nature of FRB progenitors.

The FRBs each present a different story. One of them, FRB181016, is one of the most energetic FRBs ever detected, probing into the high luminosities these events can attain. FRB170922 has the longest scattering tail published to date at around 30 milliseconds, while FRB181017 has  the shortest known at approximately 200 microseconds.

“UTMOST’s real-time detection system allows us to fully exploit its high time and frequency resolution and probe FRB properties previously unobtainable”, says ARC Laureate Fellow and project leader Prof. Matthew Bailes.

“Wael has used machine-learning on our high -performance computing cluster to detect and save FRBs from amongst millions of other radio events, such as mobile phones, lightning storms, and signals from the Sun and from pulsars”,   says project scientist Dr. Chris Flynn.

The UTMOST project is currently being augmented with a complete renovation of the North-South arm of the Molonglo Radio Telescope, allowing the source of FRBs on the sky to be pinpointed to the source galaxy they come from, and help solve the puzzle of the origin of FRBs.

The study has been submitted to the journal Monthly Notices of the Astronomical Society, and is available on arxiv as a preprint.