The famous bursting fast radio FRB20180916B barely gets caught

Two international teams of astronomers (with significant Dutch involvement) have published two scientific papers with new information about the famous fast radio explosion FRB20180916B. In a study published in Astrophysical Journal Letters, measured the radiation from the explosions at the lowest possible frequencies. In a study published in Nature Astronomy, examined the explosions in as much detail as possible. While the articles provide new information, they also raise new questions.

In 2007, the first rapid radio explosion (FRB) was discovered. But what exactly is causing the explosions is not yet clear. Since 2020, scientists have suspected a connection to highly magnetic neutron stars called magnets. One of the best known fast radio explosions is FRB20180916B. This FRB was discovered in 2018 and is only 500 million light-years away in another galaxy. The FRB is the closest so far and has an explosion pattern that repeats itself every 16 days: four days of explosions, 12 days of relative silence. This predictability makes it an ideal object for researchers.

The lowest radio signals ever

An international team of researchers led by Ziggy Pleunis (a graduate of the University of Amsterdam, now McGill University, Montreal, Canada) studied FRB with the European network of LOFAR radio telescopes. They had tuned the LOFAR antennas between 110 and 188 MHz. These are almost the lowest possible frequencies that the telescope can receive. They caught 18 explosions. This was unexpected because FRBs usually transmit at high frequencies. FRB20180916B thus breaks the low frequency record. In fact, researchers suspect that the explosion emits radiation with even lower frequencies and that it will search in the near future.

In addition to the recordings, the observations also offer new perspectives. Low-level radio broadcasts were fairly clean and were later followed by outbreaks of higher-level radio broadcasts. Co-author Jason Hessels (Dutch Institute for Radio Astronomy ASTRON and the University of Amsterdam) says: “At different times, we see radio explosions with different radio frequencies. Possibly FRB is part of a binary star. If so, we would have a different vision at different times where these extremely powerful explosions are generated. “

A team of researchers led by Kenzie Nimmo (ASTRON and the University of Amsterdam, the Netherlands) used the European VLBI radio telescope network, which includes one of 12 Westerbork ASTRON telescopes in Drenthe and the 100-meter Effelsberg telescope in Germany. They looked in the greatest detail ever at the so-called polarized microstructure of eruptions. Astronomers have seen that the explosion pattern of the FRB20180916B varies from microsecond to microsecond. The most logical explanation for the variation seems to be a “dancing” magnetosphere enveloping a neutron star.