New observations challenge popular radio burst model

Artist’s idea of the 2 radio observatories concerned in a brand new quick radio burst examine: dishes on the Westerbork Synthesis Radio Telescope (left) detected a periodic, quick sign from a quick radio burst at excessive frequencies. But the low-frequency sign from the identical supply, caught the LOFAR telescope, appeared a lot later.

Joeri van Leeuwen

Fourteen years in the past, the primary quick radio burst (FRB) was found. By now, many a whole lot of those energetic, millisecond-duration bursts from deep space have been detected (most of them by the CHIME radio observatory in British Columbia, Canada), however astronomers nonetheless wrestle to clarify their enigmatic properties. A brand new publication on this week’s Nature “adds a new piece to the puzzle,” says Victoria Kaspi (McGill University, Canada). “In this field of research, surprising twists are almost as common as new results.”

Most astronomers agree that FRBs are probably explosions on the surfaces of highly magnetized neutron stars (so-called magnetars). But it’s unclear why most FRBs look like one-off occasions, whereas others flare repeatedly. In some instances, these repeating bursts show signs of periodicity, and scientists had give you a gorgeous model to clarify this habits, involving stellar winds in binary programs.

However, new observations by European radio telescopes could rule this model out.

Astronomers knew that FRB 20180916B, positioned in a galaxy some 475 million light-years away, produces a number of bursts about each 16 days, throughout a ‘window’ that lasts for just a few days. “The idea was that the magnetar is part of a binary system with a 16.29-day period,” says Inés Pastor-Marazuela (University of Amsterdam), the primary writer of the brand new paper. If the companion star had a thick stellar wind that absorbs radio waves, the bursts would solely be seen when the magnetar was on ‘our’ aspect of the orbit, she explains.

However, simultaneous observations of FRB 20180916B by the Low-Frequency Array (LOFAR) and the 14-dish Westerbork Synthesis Radio Telescope (WSRT) within the Netherlands challenge the predictions of this model. Since stellar winds ought to higher take up lower-frequency radio waves than higher-frequency ones, astronomers anticipated that the bursts noticed by LOFAR (right down to 120 megahertz, similar to a wavelength of three meters) would solely be seen in a narrower time window than the bursts noticed by WSRT (at 1.4 gigahertz, or 21 centimeters). “We found the exact opposite,” says coauthor Joeri van Leeuwen (ASTRON Netherlands Institute for Radio Astronomy). Moreover, the height within the variety of high-frequency bursts preceded the low-frequency peak by just a few days, which additionally isn’t anticipated within the binary wind model.

“I agree that the observations are challenging for the model,” says Kaspi, who’s a part of a staff that has independently studied the LOFAR data (that are publicly accessible) however didn’t have entry to the simultaneous Westerbork observations. However, she’s not but satisfied that the binary thought is totally dominated out. “We need more sources and better statistics.”

What could possibly be another rationalization? Perhaps, says Pastor-Marazuela, the 16.29-day interval is definitely the rotation interval of the burst supply, as a substitute of its orbital interval. If the explosions originate in a small, localized area of the magnetar’s floor, this area will likely be carried out and in of sight by the compact object’s rotation.

Kaspi counters {that a} rotation interval of 16.29 days can be extremely lengthy: Magnetars (and neutron stars usually) often full tens, a whole lot, or perhaps a few thousand revolutions per minute. “But nature can be very creative,” she provides. “Never say never.”

FRB 20180916B could possibly be a really uncommon case, says van Leeuwen. In explicit, he’s stunned by the truth that no single burst was detected by each LOFAR and WSRT, although the 2 amenities had been observing concurrently. “It’s something I had never expected,” he says. But even when this explicit supply is particular, it might shed extra gentle on the properties of FRBs usually. “Think of Oliver Sacks, the famous neurologist,” van Leeuwen says. “He learned a lot about the human brain by studying his most interesting patients.”

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