China Focus: Chinese scientists detect brightest gamma-ray burst to date

BEIJING, Oct. 19 (Xinhua) -- Chinese scientists have detected the brightest gamma-ray burst (GRB) to date through combined observations from both Earth and space, according to the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences.

The combined observations were made on Oct. 9, 2022, by China's Large High Altitude Air Shower Observatory (LHAASO), the High Energy Burst Searcher (HEBS) -- an all-sky monitor for gamma-ray transients -- as well as China's X-ray astronomy satellite Insight-HXMT (Hard X-ray Modulation Telescope), achieving multi-spectral measurements of the gamma-ray burst, coded as GRB 221009A.

GRBs are immensely energetic explosions that have been observed in distant galaxies. They are the most energetic and luminous electromagnetic events since the Big Bang. Bursts can last from several milliseconds to several hours, producing as much energy as the Sun will emit during its entire existence.

The GRBs with a longer duration are generated by the collapse and explosion of stars with dozens of times the mass of the Sun, while the short bursts are produced by the merger of two compact celestial bodies, such as black holes or neutron stars, which may also be accompanied by gravitational waves, scientists say.

"GRB 221009A is a long burst, which occurred more than two billion light years away from Earth. A GRB with such huge brightness is estimated to occur only once in decades," said Zhang Shuangnan, director of the Division for Particle Astrophysics of IHEP, as well as the principal investigator of Insight-HXMT.

According to Cao Zhen, the principal investigator of LHAASO, in this observation, LHAASO detected a large number of high-energy photons, reaching a maximum photon energy of 18 TeV.

"With the combined observations of LHAASO, HEBS and Insight-HXMT, we found that this event was more than 10 times brighter than the brightest gamma-ray burst previously observed by humans," he said.

"This observation has broken several records for gamma-ray burst observations and is of great value in revealing the outburst mechanisms of gamma-ray burst," Cao added.

LHAASO, covering an area of 1.36 square km at 4,410 meters above sea level in Daocheng County, southwest China's Sichuan Province, is one of the country's key national science and technology infrastructure facilities.

Insight-HXMT, China's first X-ray astronomical satellite, sent into orbit on June 15, 2017, has made a series of discoveries concerning black holes, neutron stars and fast radio bursts over the past five years.

HEBS was sent into space on July 27, 2022, adopting a new detection technology. With the help of China's BeiDou Navigation Satellite System, it can quickly send observation data back to Earth.