Keeping the Beat

Fast radio bursts (FRBs) are notoriously difficult to study. These bright radio flashes only last milliseconds, and they usually seem to happen at random. In the past most FRBs were observed by accident, but as radio sky surveys come online we’re beginning to observe more of them. What we’re finding is quite surprising.

Recently the CHIME radio telescope has observed dozens of bursts, including several that occur multiple times from the same source. These repeating hold the most promise toward understanding these strange radio bursts.

Repeating FRBs tend to happen sporadically. Their repeating nature indicates that they aren’t due to a cataclysmic event, such as a neutron star collapsing into a black hole. But the randomness of their repetitions suggests some complex mechanism driving them. One popular idea is that they are the result of hyperflares created by highly magnetic neutron stars known as magnetars. Just as our Sun generates solar flares that create a burst of energy, magnetar hyperflares could create powerful radio bursts.

But a new study puts that idea in doubt.¹ In analyzing the repeating bursts of one particular source, the team found the FRB had a period of about 16 days. It is extremely consistent, and this suggests a periodic cause.

One idea is that it is due to the orbital period of a binary system, such as a neutron star orbiting a young OB star. OB stars are massive and highly energetic. Neutron stars are dense and have strong magnetic fields. A close binary of the two could create a beam of high energy radio light, We would see this beam as a burst when it points in our direction.

This is only one example of a regularly repeating FRB. Other repeating radio bursts don’t seem to have such regularity, so there could be multiple causes. But as more data on these bursts come in we should be able to narrow down their mysterious origins.