Uncanny Coincidence: Fast Radio Burst Detected After Gravitational Wave Event

A odd signal from space occasionally reaches our scanners on Earth.

These incredibly brief signals, known as rapid radio bursts (FRBs), have a millisecond period and can only be seen at radio frequencies.

However, they can release as much energy as 500 million Suns in those milliseconds and at those frequencies, and the majority of them have never been found again.

It's a bit of a riddle what they are and how they are produced. However, a recent finding may indicate a previously unidentified process generating these potent radiation bursts.

A brilliant, non-repeating rapid radio burst was captured by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) on April 25th, 2019. ( FRB).

Just 2.5 hours earlier, a binary neutron star impact that occurred as it approached the unavoidable end of its decaying trajectory was captured by the Laser Interferometer Gravitational-Wave Observatory (LIGO).

The FRB's position in the heavens coincided with the gravitational wave event's plausible area and was located nearby. The possibility that the two events were unrelated, a team of astronomers headed by Alexandra Moroianu of the University of Western Australia has established, is exceedingly tiny.

Only a small percentage of FRBs repeat, and the overwhelming majority of them are one-off events, making it incredibly challenging to research them.

Until recently, spotting one required luck—you had to be looking at the correct area of the sky at the right moment. However, the number of detections has grown to over 600 thanks to all-sky scans.

A significant development occurred in 2020 when a FRB was discovered for the first time originating from within the Milky Way galaxy. It was discovered that the phenomenon was caused by a particular kind of neutron star called a magnetar, whose absurdly potent exterior magnetic field battles with gravity to periodically cause the star to tremble and flare.

Although malfunctioning magnetars offer one possible reason, we are unsure if that is the whole story. FRBs have a wide range of characteristics, suggesting that multiple mechanisms may be able to generate them.

Numerous hypotheses suggest a connection between FRBs and gravitational waves, especially if neutron stars are involved, either during or after the gravitational wave discovery.

Moroianu and her coworkers started browsing inventories as a result. For a total of 171 FRB events, the CHIME collection of observations from July 2018 to July 2019 coincided with the LIGO-Virgo observation period.

In order to find FRB events that happened within the LIGO-identified region of the sky and were temporally near to gravitational wave detections, the researchers cross-referenced these events with the GWTC-2 database.

And they felt a powerful impact.

At 08:18:05 UTC on April 25, 2019, LIGO detected GW20190425. The area from which the detection had arisen was constrained by the lack of a Virgo detector detection. It was created by the merging of two neutron stars and was thought to be 520 million light-years distant.

The same day, at 10:46:33 UTC, FRB20190425A was found, with a maximum distance of 590 million light-years, within the region of the heavens LIGO had identified as a likely cause of the neutron star merger.

They discovered that if the two weren't connected, this would be a strange accident. The researchers determined that the likelihood of the two events happening at the specified distances, during the discovery period, and within the area of space specified by LIGO was only 0.00019.

The two occurrences most likely originated from a galaxy known as UGC 10667, but further investigation may be necessary to determine how the FRB was created.

The burst was thought to have been triggered, for the time being, by a blitzar, a process suggested for FRBs nearly ten years ago. When a neutron star's rotation decreases, the only thing that was keeping it from collapsing into a black hole is its mass, which is too great to be sustained by degeneracy pressure.

The collapse of a post-binary neutron star-merger magnetar is mentioned in the GW, short gamma-ray burst (sGRB), and FRB association hypothesis, which the researchers claim is consistent with the possible GW-FRB association.

The 2.5-hour delay time between the FRB and the GW event is the survival time of the supramassive neutron star before collapsing into a black hole, which is consistent with the expected range of the delay timescale for a supramassive magnetar from both theory and observational data. This scenario has been confirmed through numerical simulations.

The neutron stars in GW20190425 had masses that were considerably greater than those of the majority of neutron star pairs found in the Milky Way. The few recurring FRB sources can be explained by the fact that these lower mass binaries would create more durable heavyweight neutron stars after merging, which could live for a very long time and emit FRBs frequently.

The two occurrences may or may not have been connected, but one thing is certain: the rate of binary neutron star mergers is believed to be much, much lower than the rate at which FRBs like FRB190425A are discovered. Therefore, this possible process is insufficient to explain the puzzling signals that sputter across the radio heavens.

There is still room for more research. But the fact that we appear to be getting closer to some solutions is incredibly thrilling.

The research has been published in Nature Astronomy.