Earlier this year, astronomers announced a dazzling discovery. A rapid radio burst named FRB 121102 was not just repeated – it was repeated on a recognizable cycle.
For about 67 days, the source is silent. Then, for about 90 days, it wakes up, spits out repeated millisecond radio flights before stopping, and repeats the entire 157-day cycle.
However, rapid radio bursts are extremely mysterious, and there was no guarantee that the cycle would continue. So it’s very exciting that the resource is booming again, right on the key – consistent with predictions of its activity cycle.
This suggests that there is an important value in monitoring known sources for rapid radio bursts – but also in passing FRB 121102 to try to understand what could be causing the phenomenon.
A fast refresher: Fast radio bursts are, as the name implies, bursts of radio waves that are very fast but only a few milliseconds long, coming from galaxies millions to billions of light-years away. But they are also extremely powerful; within those milliseconds they can discharge as much power as hundreds of millions of Suns.
Most of the time they flare up once and we have not heard from them since, making them impossible to predict and very difficult to track. And we do not know what causes them, although recent evidence points to a kind of neutron star called magnetars.
But a handful of rapid sources for radio bursts have been rediscovered, and these could be one of the keys that at least in part helps the mystery.
Before the cycle was discovered by Manchester University astronaut Kaustubh Rajwade and his team, FRB 121102 was already known to be the most active rapid radio burst ever discovered, and several times since its discovery in 2012. repeated bursts out.
Because it repeats, astronomers could look at activity, and trace it to a source galaxy. It was the first rapid radio burst to be located, after a star-forming region in a dwarf galaxy 3 billion light-years away.
The discovery of periodicity in its activity – based on data of five-year value – could place some significant limitations on what it could be.
For example, high-mass X-ray binaries in the Milky Way – those containing neutron stars – can have orbital periods of up to hundreds of days. But there are some types of binary systems with much shorter periods – these can be excluded for FRB 121102.
And now periodicity is supported by new sets of observations – although timing may need revision.
A team led by Marilyn Cruces of the Max Planck Institute for Radio Astronomy discovered 36 bursts of FRB 121102 with the Effelsberg 100-m Radio Telescope between September 2017 and June 2020. Combined with data from Rajwade’s research, the received a periodical of 161 days, in a new preprint paper uploaded to arXiv.
This paper gives dates between July 9 and October 14, 2020 for the active period of the resource.
But Cruces and her team are not the only ones looking. A team led by Pei Wang of the National Astronomy Observatory of China used the Five Hundred Meter Aperture Spherical Radio Telescope to check the location of FRB 121102 on various dates between March and August 2020.
Between mid-March and late July, they did not detect any bursts. But on August 17, FAST detected at least 12 bursts of FRB 121102 – suggesting that the source is in an active phase again – although the team calculated a different periodicity from both Rajwade’s team and Cruces’ team.
“We combine the bursts that have been collected in Rajwade and others. (2020) and Cruces and others. (2020) with this newly discovered by FAST in 2019 and 2020, and get a new best fit period of ~ 156.1 days, “she wrote in a message posted to The Astronomer’s Telegram.
According to calculations by Wang’s team, the active phase is too late between August 31 and September 9, 2020. If FRB 121102 continues to show activity outside of these dates, this may suggest that it is not periodically real, or that it is on one somehow evolved, they noted in their post.
Of course, it is also possible that the periodicity calculations need to be refined. Which means we have to keep FRB 121102.
“We encourage more follow-up monitoring efforts from other radio observers,” the researchers wrote.
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