Explosive start not needed for fast radio bursts
ITHACA, N.Y. – After combing through Cornell-archived data, astronomers have discovered the pop-pop-pop of a mysterious, cosmic Gatling gun – 10 millisecond-long "fast radio bursts" – caught by the Arecibo telescope in Puerto Rico, as reported in Nature, March 2.
In the past eight years, scientists have found 17 fast radio bursts, or FRBs. Until now, scientists believed these bursts were isolated, singular events – one-time explosions from the distant corners of the universe. To their surprise, after reviewing PALFA (Pulsar Arecibo L-Band Feed Array) data from 2015, astronomers now confirm that at least some of these FRB sources emit repeated pulses.
Last week, astronomers in another Nature paper indicated the discovery of the 17th FRB, reporting a radio "afterglow" of a new FRB, which is like a mushroom cloud following a huge explosion, says Shami Chatterjee, a Cornell senior researcher. "In our paper, we're showing that our FRB can't have an explosive origin. So, either there's an odd coincidence, or maybe there are different types of FRBs. Either way, it seems we've broken this enigmatic phenomenon wide open."
Chatterjee, who measured the burst properties and searched for counterparts at other wavelengths, says this discovery rules out entire classes of theoretical models – such as explosive mergers of neutron stars – for at least this one FRB source. "This research shows for the first time that there can be multiple FRBs from the same place in the sky – with the same pulse dispersion or distance. Whatever produces the FRB can't be destroyed by the burst, because otherwise, what would produce the next pulse?"
This new cosmic riddle is perplexing, said Cornell University astronomy professor James Cordes. "We're showing that whatever battery drives FRBs, it can recharge in minutes," he said.
"The energy of the event becomes very problematic. We're detecting these FRBs from very far away, which means that they are intrinsically very bright. Only a few astrophysical sources can produce bursts like this, and we think they are most likely neutron stars in other galaxies," Cordes said, based on his own theoretical analysis conducted with his colleague Ira Wasserman, Cornell professor of astronomy.