Eight new repeating radio signals detected from deep space
Fast radio bursts (FRBs) are one of the most intriguing mysteries of modern astronomy. Picked up from all corners of the cosmos, these perplexing radio signals usually only last milliseconds before fading forever, but some particularly strange ones repeat on an irregular basis. Now the catalog of repeaters has grown substantially, as astronomers have detected a whopping eight new repeating signals.
Since the first fast radio bursts were discovered in 2007 in old data, dozens of signals have been detected. Most are one-off events, but in 2015 a burst was found coming from a location where another burst had been detected in 2012. Since then this source, known as FRB 121102, has given off well over a hundred signals, sometimes lying dormant for months, sometimes flashing dozens of times in the space of a few hours.
For years FRB 121102 was the only known repeater, but back in January this year a second was discovered, followed by a third in June. And now, it looks like the ranks are swelling with a ridiculous bumper crop of eight new repeating sources.
The incredible discovery comes courtesy of a team of astronomers led by McGill University, using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope. The astronomers observed two bursts from six of the sources, while another gave off three bursts. But one in particular really stole the show, giving off 10 bursts within four months of observations.
One of the main mysteries of FRBs is how closely related repeating and non-repeating signals are, and whether they come from the same types of objects or environments. The discovery of eight new repeaters gives astronomers a much wider toolset to work with, to help solve this problem.
Comparing the new signals to previously-known ones, the team noticed a few similarities and differences. The dispersion measures – which is how "stretched" the signal becomes as it travels across the cosmos – appear to be roughly within the same range for both types of FRB sources. That said, bursts from repeaters tend to last longer than those from non-repeaters. And finally, some of the new signals were also found to give off weaker sub-bursts after the main show.
Altogether, the team concludes that the phenomena may be coming from different sources, or at least similar sources under different conditions. After all, FRB 121102 signals have been found to be extremely twisted, meaning the source object may be very close to a black hole, nebula or supernova remnant. Not all repeaters may live in these extreme conditions, which could change their signals.
With more and more telescopes pointing skyward, the mystery of fast radio bursts feels like one that may be solved in the relatively near future.
The research has been submitted to the Astrophysical Journal Letters for potential publication.
Source: arXiv (PDF)