A Neutron Star Collision’s Cosmic Signals: Shedding Light on Fast Radio Bursts
The cosmic collision, which took place on April 25, 2019, was detected by one of the three observatories that make up LIGO. Approximately 2.5 hours after the initial detection, a fast radio burst detector picked up a signal from the same region of...
A recent study published in Nature Astronomy on March 27 suggests that a cosmic event involving neutron star pileup may have given rise to two distinct signals: gravitational waves, which are ripples in spacetime, and a fast radio burst, a fleeting burst of energy. This discovery could provide crucial insights into the mysterious origin of fast radio bursts (FRBs) and bolster the theory that neutron star mergers contribute to their generation.
The cosmic collision, which took place on April 25, 2019, was detected by one of the three observatories that make up LIGO. Approximately 2.5 hours after the initial detection, a fast radio burst detector picked up a signal from the same region of the sky. Astrophysicist Alexandra Moroianu, who discovered the merger and its aftermath, says that while they are 99.5 percent sure the signals came from the same event, they aim to reach 99.999 percent certainty. Unfortunately, LIGO’s other two detectors did not detect the signal, making it difficult to pinpoint the exact location of the event.
Fast radio bursts, first observed in 2007, have puzzled astronomers ever since, with over 600 occurrences documented so far. One leading explanation for their origin involves magnetars, highly magnetized neutron stars left behind after massive stars explode. However, the fact that some FRBs repeat while others appear to be one-time events has led scientists to believe that there may be multiple ways to produce them.
The recent finding lends support to the hypothesis that a collision between two neutron stars could generate a singular fast radio burst before the debris from the collision forms a black hole. Researchers believe that such an event would also emit gravitational waves. Moroianu and her team searched archived data from LIGO and the Canadian Hydrogen Intensity Mapping Experiment (CHIME), a fast radio burst detector in British Columbia, and found a potential pairing: GW190425 and FRB20190425A.
Despite the uncertainty surrounding the exact cause of the signals, astrophysicist Alessandra Corsi believes the finding has exciting implications. One possibility is that two neutron stars could merge into a single, extra-massive neutron star without immediately collapsing into a black hole. This discovery could help scientists better understand neutron matter behavior and refine the fuzzy dividing line between neutron stars and black holes.
Astrophysicist Bing Zhang had earlier suggested that a neutron star collision could create an extra-massive neutron star that wobbles on the edge of stability for a few hours before collapsing into a black hole. In such a case, the resulting FRB would be delayed, just as observed in the 2019 event. The most massive neutron star ever observed weighs about 2.35 times the mass of the sun, but theorists believe they could grow to be around three times the sun’s mass without collapsing.
As the next LIGO run is set to begin in May, researchers are optimistic that more coincidences between gravitational waves and FRBs will be discovered, now that they know what to look for. Corsi says, “There should be a bright future ahead of us.”
A. Moroianu et al. An assessment of the association between a fast radio burst and binary neutron star merger. Nature Astronomy. Published online March 27, 2023. Doi:10.1038/s41550-023-01917-x.
B. Zhang. A possible connection between fast radio bursts and gamma-ray bursts. The Astrophysical Journal Letters. Published December 16, 2013. Doi: 10.1088/2041-8205/780/2/L21.