Scientific collaboration detects more than 500 mysterious rapid radio bursts in its first year of operation

Scientists from the Canadian Collaboration for Hydrogen Intensity Mapping Experiment (CHIME), which include researchers from the Tata Institute for Fundamental Research (TIFR) in Pune and the National Center for Radio Astrophysics (NCRA), assembled the largest collection of rapid radio bursts (FRBs) in the telescope’s first FRB catalog.

Although spotting an FRB is considered a rare thing in radio astronomy, prior to the CHIME project, radio astronomers had only seen about 140 bursts within their scope since the first FRB was spotted in 2007.

FRBs are strangely bright flashes of light, registering in the radio band of the electromagnetic spectrum, which flare up for a few milliseconds before disappearing without a trace. These brief and mysterious beacons have been spotted in various remote parts of the universe, as well as in our own galaxy. Their origins are unknown and their appearance is highly unpredictable.

But the advent of Project CHIME – a large stationary radio telescope in British Columbia, Canada – was a game-changer and nearly quadrupled the number of rapid radio bursts discovered to date. With more observations, astronomers hope to soon pinpoint the extreme origins of these curiously bright signals.

The telescope detected 535 new rapid radio bursts during its first year of operation, between 2018 and 2019.

“Prior to CHIME’s arrival, different telescopes had observed a handful of FRBs each, but with their own selection criteria and software. But now, with the help of CHIME, we can observe a large part of the sky around the clock and have been able to detect FRBs at an unprecedented rate. We were able to assemble the first large sample of FRBs with a single instrument and a single well understood selection criterion, which allows us to better understand the properties of FRBs as a population, ”said Shriharsh Tendulkar, CHIME / FRB member. . , also a faculty member of TIFR-NCRA.

The new catalog considerably expands the current library of known FRBs and already gives clues to their properties. For example, the newly discovered bursts appear to belong to two distinct classes: those that repeat and those that do not repeat. Scientists have identified 18 FRB sources that have erupted multiple times, while the rest appear to be one-time.

When the scientists mapped their locations, they discovered that the bursts were evenly distributed in space, appearing to come from all parts of the sky. From the FRBs that CHIME was able to detect, scientists calculated that rapid and bright radio bursts occur at a rate of about 800 per day across the sky – the most accurate estimate of the overall FRB rate at this time. day.

The first FRB catalog is due to be presented later this week at the American Astronomical Society meeting.

Mr Tendulkar said observations showed the repeaters looked different, with each burst being slightly longer in duration and emitting more focused radio frequencies than the non-repeating single FRB bursts.

“We find that repeaters emit longer bursts with radiation being detected in a narrower frequency range compared to single FRBs. These differences strongly suggest that the emission of repeaters and non-repeaters is generated either by different physical mechanisms or in different astrophysical environments, ”said Pragya Chawla, PhD student. candidate at McGill University and member of the CHIME team.

CHIME comprises four massive cylindrical radio antennas, roughly the size and shape of snowboard half-moons, located at the Federal Radio Astrophysical Observatory, operated by the National Research Council of Canada in British Columbia. The telescope receives radio signals from half the sky every day as the Earth rotates.

While most radio astronomy is done by rotating a large dish to focus light from different parts of the sky, CHIME stares at the sky, still, and concentrates the incoming signals using a correlator – a powerful processor. of digital signal that can process data, at a rate of about seven terabytes per second, which is equivalent to a few percent of global Internet traffic.

“Digital signal processing is what allows CHIME to simultaneously reconstruct and ‘look’ in thousands of directions. This is what helps us detect FRBs a thousand times more often than a traditional telescope, ”says Kiyoshi Masui, assistant professor of physics at the Massachusetts Institute of Technology (MIT), who will lead the group’s presentation at the meeting. the American Astronomical Society.

For each of the 535 FRBs detected by CHIME, Professor Masui and his colleagues measured its dispersion and found that most of the bursts were likely from distant sources within 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, he said. As the telescope detects more FRBs, scientists hope to determine exactly what kind of alien phenomenon could generate such super bright, super fast signals.

According to Professor Masui, the scientists plan to use the bursts and their dispersion estimates to map the distribution of gas in the universe.