Fast radio bursts from deep space have never been seen to repeat — until now.
Ten blasts of radio waves recorded last May and June all come from the same direction, researchers report online March 2 in Nature. So did a signal detected in 2012, say Laura Spitler, an astrophysicist at the Max Planck Institute for Radio Astronomy in Bonn, Germany, and colleagues. All 11 signals were detected at the Arecibo Observatory in Puerto Rico.
Fast radio bursts, or FRBs, last a few milliseconds and, except for one, all appear to originate in other galaxies (SN: 8/9/14, p. 22). For the repeater, each of the signals encountered the same amount of intergalactic plasma, meaning they traveled the same distance. That shared feature makes an ironclad case for a common source, says Duncan Lorimer, an astrophysicist at West Virginia University in Morgantown and co-discoverer of the first FRB, reported in 2007. The question now is what fraction of sources repeat, he says. There may be multiple classes of FRBs, with some recurring and some not, each triggered by something different.
Explanations for what causes FRBs include colliding stellar cores, overzealous pulsars and the collapse of obese neutron stars. A repeating signal rules out one-off scenarios such as collisions. More likely sources are radio eruptions from various types of neutron stars, such as pulsars and magnetars. Pulsars emit a steady beat of radio waves, but some young pulsars, such as the nearby Crab pulsar, occasionally blast out vigorous pulses. Radio telescopes could detect such large blasts from another galaxy, Spitler says.
With a known repeater, a facility like the Very Large Array near Socorro, N.M., could stare at the same patch of sky, wait for the next eruption and identify the host galaxy (SN Online: 2/26/16). “It’s a wake-up call that there’s a lot we can do with existing FRBs,” Lorimer says.