“Glitches” in Neutron Stars Could Decipher the Enigma of Mysterious Radio Bursts

Astronomers have made significant progress in understanding the enigmatic phenomenon of fast radio bursts (FRBs), thanks to a magnetar in our own galaxy. FRBs are brief but incredibly intense flashes of radio waves, and until recently, were mostly detected from far-off galaxies. However, in April 2020, a magnetar named SGR 1935+2154 located in our galaxy emitted an FRB-like burst, offering astronomers a closer object of study.

Magnetars are highly magnetized neutron stars, and their connection with FRBs was established when SGR 1935+2154 emitted another burst in October 2022. Observations from NASA’s Integral space telescope’s Burst Alert System led to this discovery. The Neutron Star Interior Composition Explorer (NICER) and the Nuclear Spectroscopic Telescope Array (NuSTAR), two other NASA space telescopes, were then directed towards the magnetar for further study.

The neutron star was observed to exhibit a pulsating brightness due to a hotspot on its surface, likely marking one of its magnetic poles. Significant changes were observed within hours, including a sudden increase in spin speed, a gradual decrease in rotation rate over four hours, and a burst of radio waves, followed by another increase in spin speed.

These anomalies were likely caused by a phenomenon known as a “glitch,” where the surface of the neutron star is out of sync with its interior, resulting in a temporary increase in rotation speed. This glitch, according to the team, could have resulted from a “starquake,” a rupture in the star’s crust caused by stress from motions beneath the surface.

The team hypothesizes that the starquake released a large number of charged particles, which in an extremely strong magnetic field lead to the creation of electron-positron pairs in an “avalanche” process. This could be the mechanism for the sudden burst of radio emission, resembling a laser-like process.

These observations have linked a rare FRB-like burst to a rare double glitch, providing a clear path for further investigations into FRB generation. However, whether this scenario applies to all FRBs remains an open question. As of now, the 2020 and 2022 bursts from SGR 1935+2154 are the only truly “loud” bursts of radio waves detected, but milder activity occurs more often. The team plans to continue monitoring the magnetar to catch more bursts in the future, which will provide additional data to help test the wind/pair creation scenario.

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