FRB 20220912A sets a new FRB burst rate record

Observations capture a repeating signal from a hyperactive fast radio burst in a clear environment, offering astronomers valuable insights into its origin. Fast Radio Bursts (FRBs) are enigmatic high-energy signals that occur on extremely short timescales, releasing an immense amount of energy equivalent to several days’ worth of the Sun’s output in just milliseconds. The origin of FRBs remains unknown, with astronomers working to differentiate the original signal from interference caused by its journey through space. Now, a “clean” FRB signal has been detected, raising hopes among astronomers for new insights into the sources of these cosmic outbursts.

Photo credit: Green Bank Observatory

U.S. National Science Foundation Green Bank Telescope:  FRB 20220912A sets record for fastest fast radio burst to date

Using the U.S. National Science Foundation's Green Bank Telescope (NSF GBT), an international team of astronomers led by Yi Feng of China’s Research Center for Astronomical Computing has recorded FRB 20220912A, which emitted 128 bursts in less than two hours, setting a new burst rate record for this class of radio telescope.

Originally discovered by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) team, the NSF GBT observations by Feng’s team confirmed FRB 20220912A as a hyperactive, repeating FRB. “This FRB is very special because we detected over 100 bursts in just a few hours – the highest burst rate ever detected by GBT — showing us that this FRB is very active,” Feng noted.

Of the over 800 known FRBs, less than ten percent are repeating. The majority of FRBs originate outside the Milky Way, with their energy often interacting with clouds of dust, gas, and free electrons along their path. These interactions, influenced by magnetic fields, introduce distortions to the FRB signal.

Feng’s observations suggest that FRB 20220912A may be one of the “cleanest” repeating FRB signals detected to date. Two structural features of a repeating FRB signal can provide clues about its source’s environment: polarization and the Faraday rotation measure.

Polarization, an indicator of the incoming radio waves’ directionality, reveals information about the signal's journey. In FRB radio signals, waves usually arrive with linear polarization, suggesting multiple interactions with electrons, gas, and dust. Circular polarization, however, indicates minimal interference, suggesting a pristine source environment. Before Feng’s observations of FRB 20220912A, only three repeating FRBs with circular polarization had been observed, all located in complex environments. FRB 20220912A, however, appears to provide an unusually clear signal, offering astronomers a rare opportunity for closer examination.

The second feature, Faraday rotation measure, reflects both the magnetic field and electron density along the signal’s path. High values imply a dynamic environment with likely magnetic field changes, while low rotation measures point to a stable, calm source region. FRB 20220912A shows both circular polarization and a low rotation measure, both of which indicate an unobstructed environment conducive to clear signal propagation.

Feng and his team plan to conduct further long-term observations of FRB 20220912A to deepen understanding of its nature. This research has been published in The Astrophysical Journal.

The National Radio Astronomy Observatory (NRAO) and Green Bank Observatory (GBO) are prominent facilities supported by the U.S. National Science Foundation, operated under a cooperative agreement by Associated Universities, Inc.