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ZJ Lab’s Chief Computational Astronomer LI Di’s Team Discovers the First Persistently Active FRB
Date: 2022-06-09

Recently, an international team led by LI Di, chief computational astronomer of ZJ Lab and researcher of the National Astronomical Observatories of the Chinese Academy of Sciences (CAS), discovered a persistently active repeating fast radio burst (FRB) coded FRB 20190520B, so far the only one of its kind, through the Commensal Radio Astronomy FAST (Aperture Spherical Radio Telescope) Survey (CRAFTS). The finding was published in the international academic journal Nature on June 9, 2022, Beijing time.

According to observations   of a number of sets of ground and aerial equipment worldwide and data from   radio interference arrays, optical and infrared telescopes and high-energy   extraterrestrial observatories, FRB 20190520B came from a metal-poor dwarf galaxy   3 billion light-years away, where the largest known electron density was   identified and the second known Persistent Radio Source (PRS) of FRB was   found.   

The findings indicate that   the complicated environment of active repeating FRBs has the characteristics   of an ultra-luminous supernova explosion. This is a challenge to the   traditional FRB dispersion analysis and lays a foundation for modeling FRB   evolution and understanding this violent and mysterious cosmic phenomenon.  

FRBs are the brightest   radio bursts in the cosmos. The energy an FRB releases in a millisecond   equals to a whole year’s solar radiation. FRB is a young science. In 2007, it   was confirmed that FRBs exist. The first repeating FRB was detected in 2016   which rewrote existing knowledge on FRB. Today, FRB is one of the newest astronomic   hot spots. Globally, nearly 500 FRBs have been made public, less than 10 of   which are recorded with active bursts, namely frequent bursts during their   burst windows. No persistently active repeating FRB had been detected before   FRB 20190520B   

FRB 20190520B, discovered   through FAST, is a clear analogue to FRB 20121102A detected by Arecibo   Telescope of the USA in 2016. FRB 20121102A is the first known repeating FRB   and the first located FRB, and was the only FRB identified with a compact   radio source. Both FRB 20190520B and FRB 20121102A are active and have a   complicated electromagnetic environment. However, FRB 20190520B has extreme   characteristics in various aspects. For example, FRB 20121102A has active   periods, while FRB 20190520B never takes a rest - FAST has detected hundreds   of its explosions. The preliminary findings of the study, once published,   have drawn wide attention in the astronomic circle and have inspired many   innovative models and articles such as the dispersion time scale model and   explanations of supernova explosion.  

Based on recent FAST   observations, FRB20121102A and FRB 20190520B are possibly newborn FRBs.   FAST’s continuous observations and, particularly, CRAFTS, a major project   with priority, are likely to help portray a new evolution diagram of FRB.   

Founder of FRB study   Duncan Lorimer commented, “Based on the characteristics of FRB 20190520B and   the existence of its PRS, I think there may be different classifications of   FRBs. As the sample of FRBs continues to grow, it is expected that in the   next few years, intriguing classes of objects in FRBs will be explained in   detail.”  

At least 6 new FRBs have   been discovered so far through CRAFTS of FAST, which is working to reveal the   mechanism of this mysterious phenomenon in the universe and promote research   in this new field of astronomy.

FENG Yi, one of FRB   20190520B discoverers and researcher of ZJ Lab’s computational astronomy   team, shared some of the FRB’s polarization analysis results in his article   published in Science on March 18, 2022, which are important for the   study of FRB 20190520B’s environment.