The repetition of fast radio bursts remains a mystery to astronomers, but these new findings could lead to key answers about them and also provide insight into other mysteries of the cosmos.
Fast radio bursts, or FRBs, are short, powerful pulses of radio waves detected from space. Some can last up to three seconds, while others appear and disappear in a fraction of a millisecond. However, their origin is a mystery. Given the amount of energy they carry, researchers assume they are produced by some of the most energetic events in the universe – supernovae, gamma-ray bursts or collisions between neutron stars, pulsars or black holes. The only thing known for certain is that most FRBs come from outside our galaxy.
This artist’s impression shows a fast radio burst traveling between its source in a distant galaxy (top left) to Earth in the Milky Way (bottom right), passing through the halo of an ongoing massive galaxy of road. Credit: ESO/M. Kornmesser
It has been more than 15 years since the first FRB was detected from space. Meanwhile, hundreds more have been discovered, but astronomers are still nowhere near pinpointing exactly what causes them.
Even more confusing are the few FRBs found that repeat periodically. So far, of the hundreds of FRBs detected, only 25 belonged to a particular class called repetitive FRBs.
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Find what was missed
In new research, a Canadian-led team of astronomers has discovered another 25 repeating FRBs, doubling the number already discovered.
The researchers found them by performing the first-ever exploration of all data collected between September 2019 and May 2021 by the Canadian Hydrogen Intensity Mapping Experiment. CHIME is a unique and highly sensitive radio telescope at the Dominion Radio Astrophysical Observatory near Penticton, British Columbia, located on the traditional, ancestral and unceded territory of the Syilx/Okanagan people.
The four ‘cylinders’ of the CHIME radio telescope are fixed in place, staring up at the sky from the ground in the Okanagan Valley in southern British Columbia. Credit: CHIME Collaboration
“Many seemingly unique FRBs simply have not yet been observed long enough for a second burst from the source to be detected,” said Dr. Ziggy Pleunis, postdoctoral researcher at the Dunlap Institute for Astronomy and Science. astrophysics from the University of Toronto. of the approximately 60 scientists involved in this new study.
“We need a longer observation time because some repeaters might repeat every 10 years. We just don’t know. They don’t play to our timescales,” added co-author Adam Dong, holder of a doctorate. student in the Department of Physics and Astronomy at the University of British Columbia.
Of the 25 newly discovered repetitive FRBs, most were spotted two or three times during CHIME observations. During the same period, one of them – FRB 20201124A, first spotted in 2020 and originating from a nearby galaxy – was seen repeating itself a total of 12 times!
This sky map, taken from the new research study, shows the locations of all repeated fast radio bursts detected so far. Credit: CHIME/FRB Collaboration/The Astrophysical Journal
Selecting these signals forced the team to develop new statistical tools to sift through the CHIME data.
“We can now accurately calculate the probability that two or more bursts from similar locations are not just a coincidence,” Pleunis explained. “These new tools were essential for this study and will also be very useful for similar research in the future.”
One of the challenges of studying FRBs is that it is impossible to predict when an FRB will appear. In most cases, astronomers can only point their radio telescopes skyward and hope to pick up one or more of these signals during their observing time. Some researchers have predicted that thousands of people could be triggered across the sky every day. However, we only detect a small number of them due to the limited amount of celestial currents that radio telescopes can scan at any one time.
Finding repeating FRBs is even trickier. Indeed, the radio telescopes must be pointed at the same part of the sky during each repeated signal. So, without knowing the timing of rehearsals, it becomes even more dependent on luck.
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CHIME sweeps FRBs
In operation since 2017, CHIME observes the entire sky above it at once, ready to intercept any signals from space that appear in its field of view. Also, while optical telescopes usually have to wait until night to observe, radio astronomy can be done day or night. Thus, when the Earth rotates, CHIME can scan the entire northern half of the celestial sphere every day.
In its first year alone, CHIME has recovered over 500 FRBs. According to the CHIME collaboration, by mid-2020 the telescope had detected well over 1,000.
Watch below: A full day time-lapse of CHIME observations
CHIME is a great tool for detecting FRBs, but it has its limitations. As it is related to the rotation of the Earth, the telescope’s field of view sweeps through space, much like the cone of light from a lighthouse. So while it can cover the entire northern celestial sphere in a day, the number of FRBs it detects and the number of repeating FRBs it finds depends on exactly what part of space it is observing at a given time. If the timing of an FRB – repeating or not – is off by even the smallest amount, such that the source is below the CHIME horizon when the signal arrives here, the telescope will still miss it.
However, if there were more telescopes like CHIME, astronomers could cover a lot more space at once, capturing a lot more FRBs and discovering more repeats.
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Why is this important?
The researchers believe their new techniques will help find even more repeating FRBs. Other telescopes can then observe these discoveries at the right time to pick up the repeated signals.
“Repeating FRBs are excellent targets for other telescopes, including ones that can measure their positions very precisely, and let us know which galaxies they came from,” said co-author Dr. Dr. Ingrid Stairs, professor in the department at the University of British Columbia. physics and astronomy, according to UBC News. “In the long term, we hope to learn a lot about their origins.”
“FRBs are likely produced by the remnants of explosive stellar deaths.” Pleunis, referring to neutron stars, pulsars and black holes, or phenomena such as gamma-ray bursts. “By studying repeating FRB sources in detail, we can study the environments in which these explosions occur and better understand the final stages of a star’s life. We can also learn more about the material that is expelled before and during the disappearance of the star, which is then returned to the galaxies in which the FRBs live.”
Additionally, detecting more repeating FRBs may help astronomers uncover the answers to other questions about the universe.
“An exciting avenue of research is to use them to measure the amount of matter between galaxies, or the intergalactic medium,” Adam Dong explained in the UBC press release.
Additionally, in addition to the 25 confirmed repeat FRBs found in this study, the researchers identified 14 other possible candidates. While there are significant enough differences between repeated bursts for these candidates – in position, dispersion, timing, etc. – if they can be confirmed as true repeaters, it could reveal even more about these mysterious phenomena.
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