The home galaxy of a second repeating fast radio burst is a puzzle

Brief, brilliant flashes of radio waves have been traced back to a galaxy that looks like the Milky Way — a radically different environment from where astronomers have seen similar radio flares before.

Until now, the only source known for a recurrent fast radio burst like this was a tiny, star-forming dwarf galaxy (SN: 1/4/17), while nonrepeating bursts have been tracked back to more massive, mellow galaxies. That implied that the two varieties of fast radio bursts, or FRBs, might have different sources (SN: 6/27/19).

But astronomers have pinned a second repeating FRB to an entirely different kind of host galaxy: a star-forming spiral, similar in size to our own galaxy, about 500 million light-years away. That observation, reported online January 6 in Nature, suggests that a whole menagerie of galactic environments may generate FRBs.

“There needs to be a theory that can explain this diversity of environments, or … there are multiple different sources for fast radio bursts,” says Jason Hessels, an astrophysicist at the University of Amsterdam.

To identify the home of this second repeating FRB, originally spotted by the Canadian Hydrogen Intensity Mapping Experiment in British Columbia (SN: 8/14/19), Hessels’ team aimed eight radio telescopes in the European VLBI Network at this burst in June 2019. Combining the telescopes’ observations allowed the researchers to triangulate the FRB’s exact position in the sky. They then used the Gemini North telescope in Hawaii to image its spiral galaxy host.

The nature of this galaxy implies that the FRB may have a different engine than the repeater in the dwarf galaxy, thought to have the conditions necessary to forge highly magnetized neutron stars that could power repeated bursts (SN: 1/10/18). But in the case of the spiral, “there’s no reason why this type of galaxy should produce any particularly exotic type of neutron star,” Hessels says. Instead, he imagines that a black hole gobbling up material could account for the blinking FRB.