Observations in the first year of operation double the number of known radio outbreaks and reveal two types: disposable and repeaters.
To spot a fast radio burst is to be extremely lucky in where and when you point to your radio bowl. Fast radio bursts or FRBs are strangely bright flashes of light that are detected in the radio band in the electromagnetic spectrum, which flares for a few milliseconds before disappearing without a trace.
These short and mysterious lighthouses have been seen in different and distant parts of the universe as well as in our own galaxy. Their origin is unknown and their appearance is unpredictable. Since the first one was discovered in 2007, radio astronomers have only spotted about 140 eruptions in their range.
Now, a large stationary radio telescope in British Columbia has nearly quadrupled the number of fast radio bursts discovered to date. The telescope, known as the CHIME, for the Canadian Hydrogen Intensity Mapping Experiment, has detected 535 new fast radio bursts during its first year of operation between 2018 and 2019.
Researchers with the CHIME collaboration, including researchers at WITH, have collected the new signals in the telescope’s first FRB catalog, which they will present this week at the American Astronomical Society Meeting.
The new catalog significantly expands the current library of known FRBs and already provides clues about their properties. For example, it seems that the newly discovered bursts fall into two different classes: those that are repeated and those that do not. Researchers identified 18 FRB sources that burst repeatedly, while the rest appear to be one-time relationships. The repeaters also look different, with each burst lasting slightly longer and emitting more focused radio frequencies than bursts from single, non-repeating FRBs.
These observations strongly suggest that repeaters and one-time occurrences originate from separate mechanisms and astrophysical sources. With several observations, astronomers soon hope to find out the extreme origin of these strangely bright signals.
“Before CHIME, there were less than 100 FRBs detected in total; now, after a year of observation, we have discovered hundreds more, ”says CHIME member Kaitlyn Shin, a graduate student at MIT’s Department of Physics. “With all these sources, we can really begin to get a picture of what FRBs look like as a whole, what astrophysics might drive these events, and how they can be used to study the universe in the future.”
CHIME consists of four massive cylindrical radio antennas, approximately the size and shape of snowboarding half-tubes, located at the Dominion Radio Astrophysical Observatory operated by the National Research Council of Canada in British Columbia, Canada. CHIME is a stationary matrix without moving parts. The telescope receives radio signals every day from half the sky as the earth rotates.
While most radio astronomy is done by rotating a large bowl to focus light from different parts of the sky, CHIME stares movably at the sky and focuses incoming signals using a correlator – a powerful digital signal processor that can work through huge amounts of data with a speed of approx. 7 terabits per second, equivalent to a few percent of the world’s internet traffic.
“Digital signal processing is what enables CHIME to reconstruct and ‘see’ in thousands of directions simultaneously,” said Kiyoshi Masui, assistant professor of physics at MIT, who will lead the group’s conference presentation. by detecting the FRB a thousand times more often than a traditional telescope. ”
During the first year of operation, CHIME 535 discovered new fast radio bursts. As the scientists mapped their locations, they found the eruptions evenly distributed in space and apparently originated from all parts of the sky. From the FRBs that CHIME was able to detect, the researchers calculated that bright fast radio bursts occur at a rate of approx. 800 pr. Day across the sky – the most accurate estimate of FRB’s total speed to date.
“It’s such a beautiful thing in this field – FRBs are really hard to see, but they’re not uncommon,” said Masui, a member of MIT’s Kavli Institute for Astrophysics and Space Research. “If your eyes could see radio flashes like you can see camera flash, you would see them all the time if you just looked up.”
Mapping the universe
When radio waves move across space, any interstellar gas or plasmaalong the way can distort or disperse the properties and trajectory of the wave. The degree of scattering of a radio wave can give clues as to how much gas it passed through and possibly how much distance it has traveled from the source.
For each of the 535 FRBs discovered by CHIME, Masui and his colleagues measured its spread and found that most of the bursts probably originated from distant sources in distant galaxies. The fact that the bursts were bright enough to be detected by CHIME suggests that they must have been produced by extremely energetic sources. As the telescope detects multiple FRBs, scientists hope to find out exactly what kind of exotic phenomena can generate such ultra-light, ultra-fast signals.
Scientists also plan to use bursts and their scattering estimates to map the distribution of gas throughout the universe.
“Each FRB gives us some information about how far they have propagated and how much gas they have propagated through,” Shin says. “With a large number of FRBs, we can hopefully find out how gas and matter are distributed on very large scales in the universe. So alongside the mystery of what FRBs are in themselves, there is also the exciting potential for FRBs as powerful cosmological probes in the future. ”
This research was supported by various institutions, including the Canada Foundation for Innovation, the Dunlap Institute for Astronomy and Astrophysics at the University of Toronto, the Canadian Institute for Advanced Research, McGill University, and the McGill Space Institute through the Trottier Family Foundation and the University of British Columbia.