A recently discovered, rare and persistent rapid-fire fast radio burst source – sending out an occasional and informative cosmic ping from more than 3.5 billion light years away – aids in the discovery of the secrets of the blazing hot space between galaxies. That’s according to an international team of astronomers, whose findings were published in the journal Nature.
The Five-hundred-meter Aperture Spherical Radio Telescope (FAST) in Ghizou province, southwest China, discovered Fast Radio Burst 20190520B, a prolific repeating burst source, in June 2019. Astronomers generally regard this telescope as the spiritual successor to the now-defunct Arecibo Observatory in Puerto Rico, which was built by Cornell University.
A rare and persistent rapid-fire fast radio burst source – sending out an occasional and informative cosmic ping from more than 3.5 billion light years away – is now assisting in the discovery of the secrets of the boiling hot space between galaxies. What excites astronomers about repeating fast radio bursts (FRBs) – which generally only burst once – is that these rapid-fire surges provide a pathway for scientists to comprehend the perplexing, mysterious, and million-degree intergalactic medium.
The persistent emission fades away as the burst repetition rate slows down. This is still very much a hypothesis, and we are eager to test it with more examples of repeating FRBs.
Shami Chatterjee
Following the discovery of the burst by FAST, scientists used the Very Large Array in Socorro, New Mexico, to pinpoint its location. What excites astronomers about repeating fast radio bursts (FRBs) – which, in general, only burst once – is that these rapid-fire surges provide a pathway for scientists to comprehend the perplexing, mysterious, and million-degree intergalactic medium.
Joining Chatterjee on the Nature paper are James M. Cordes, professor of astronomy and Stella K. Ocker, a doctoral student in astronomy. Co-author Di Li, is the chief scientist of both FAST and the radio division of the National Astronomical Observatories of Chinese Academy of Sciences. The observatory has discovered more than 100 pulsars and more than 5 FRBs.
Four bursts were detected during the initial 24-second scan in 2019, according to the paper. Between April and September 2020, during follow-up observations, FAST detected 75.
Astronomers believe that FRB 20190520B is quite young due to the rapidly repeating bursts. “It appears to reside in a complex plasma environment, similar to that expected in a young supernova remnant,” Chatterjee said. “One possibility is that the highly active source is a newborn, and if so, it paints an intriguing evolutionary picture of FRB sources, in which young burst sources are associated with persistent radio emission.”
“The persistent emission fades away as the burst repetition rate slows down,” Chatterjee explained. “This is still very much a hypothesis, and we are eager to test it with more examples of repeating FRBs.”
Astronomers usually assume that FRBs pass through only a modest amount of gas (free electrons) in their host galaxies, which makes counting electrons in the intergalactic medium an easier task. FRB 20190520B shows the opposite: It has encountered far more gas in its host galaxy than scientists expected, calling into question previous assumptions.
Finally, astronomers want to know how the intergalactic medium is formed. “We want to deconstruct how many free electrons are in the intergalactic medium because it has been extremely difficult to study,” Ocker said. “We don’t know much about it.”
“This particular new repeating FRB behaves in extreme, surprising ways,” Ocker said. “The surrounding environment is extraordinarily complex and dynamic, providing us with critical clues to the mysterious origins of FRBs.” FRB 20190520B emphasizes the importance of identifying and characterizing FRB host galaxies before using them as probes of the intergalactic medium.”
