IT Home reported on March 29 that it learned from the official official account of the Institute of particle physics of the Chinese Academy of Sciences that at 2:00 a.m. Beijing time on March 29, the Institute of particle physics of the Chinese Academy of Sciences (hereinafter referred to as the Institute of High Energy Physics) and more than 40 scientific research institutions around the world jointly released the research results of GRB 221009A, the brightest gamma ray bursts (hereinafter referred to as gamma bursts) so far. The Insight HXMT satellite and the Polar Space Telescope (GECAM-C) led by the Institute of High Energy have successfully measured the instantaneous radiation and early afterglow of the gamma storm with the highest international accuracy in the hard X-ray and soft gamma energy bands. They not only found that it has the highest brightness observed so far, increasing the brightness record of the gamma storm by 50 times, but also found that its isotropic energy has broken records, It is equivalent to releasing all the energy of eight solar mass in one minute, and also reveals that it produces extremely narrow, extremely bright jets moving close to the speed of light, making a unique contribution to the research of this once in a thousand year celestial burst. This work was completed by an international cooperation team led by the Key Laboratory of Particle Astrophysics of the Chinese Academy of Sciences, with members from more than 30 research institutions in China, the United States, Italy, France and Germany. The corresponding author of the paper are researchers Xiong Shaolin and Zhang Shuangnan from the Institute of High Energy and Professor Zhang Bing from the University of Nevada, Las Vegas (the paper has been published online at arXiv: 2303.01203).

It is worth pointing out that in the observation of this historic gamma storm, the High Altitude Cosmic Ray Observatory (LHAASO) led by High Energy conducted joint observations with the Comet satellite and the Polar Space Telescope. Among them, the High Altitude Cosmic Ray Observatory made several important first discoveries using its large amount of very high energy observation data, which will be released later.

Gamma bursts are the most severe explosive phenomena after the Big Bang, including two types. One type is the core collapse explosion that occurs in a massive star, with a duration usually longer than 2 seconds. The discovered gamma bursts belong to this category; The other is the combination explosion of two extremely dense objects (neutron star, black hole, etc.), which usually lasts less than 2 seconds and emits gravitational waves at the same time. The explosion of these two kinds of celestial bodies can produce an extremely dense celestial body, such as a black hole or a neutron star, which engulfs the surrounding matter through strong gravity and ejects matter from the poles at a speed close to the speed of light, forming a pair of jets in opposite directions. The process of shock wave or magnetic reconnection inside the jet accelerates charged particles to produce gamma ray radiation, which is called transient radiation. The interaction between the jet and the surrounding interstellar medium can also produce radiation, called afterglow. Only when the jet is aligned with Terrestrial Time can humans have the opportunity to detect these radiation.

Since the first gamma storm was discovered by humans in 1967, nearly 10000 cases of gamma storms have been detected. On October 9, 2022, numerous astronomical facilities worldwide, including the space and ground observation equipment led by High Energy, observed the brightest gamma storm (GRB 221009A) to date, which occurred in the depths of the universe 2.4 billion light-years away from Earth. The extreme brightness and relatively close proximity of this gamma storm make it a truly historic event that occurs once in a thousand years.

The Polar Space Telescope specially built in China to detect the electromagnetic counterparts of gamma storms and gravitational waves, in conjunction with China's first space X-ray astronomical telescope, the Comet Satellite, accurately characterized the radiation properties of each critical stage of the gamma storm from precursor radiation to main storm, flare, and early afterglow in the hard X-ray and soft gamma ray energy bands. Among them, the Polar Space Telescope is in a special observation mode that can record extremely high gamma ray intensity, avoiding various instrumental effects that are easily caused by extreme brightness (including data saturation loss, signal accumulation, excessive dead time, etc.), and successfully detected the bright main storm at the extreme end of the gamma storm completely and accurately. The high-energy X-ray telescope equipped by Huiyan Satellite successfully detected the GRB and obtained high-quality data of its precursor radiation and early afterglow by virtue of its largest effective area in the MEV energy region.

Based on precise observation data from the Polar Space Telescope, the research team found that the gamma storm had the highest brightness detected so far, and increased the brightness record of the gamma storm by 50 times! Due to the distance from Earth of the gamma storm, for all the gamma rays it emits, what we detect is only a drop in the ocean. Usually, we cannot know how much energy a gamma storm radiates in directions beyond our line of sight. Assuming that a gamma storm radiates almost the same amount of gamma rays in all directions, based on the distance between the detected gamma rays and the gamma storm, we can calculate the total energy of all gamma rays emitted by the gamma storm in all directions, which is isotropic energy. The research team found that the isotropic energy of this GRB also broke the record, exceeding the 55th power of 10, which is equivalent to releasing all the energy of 8 solar mass in one minute!

The joint observation results of Huiyan and Jimu can speculate that the inflection of the afterglow of the gamma storm from slow decay to fast decay occurred very early, indicating that the jet generating gamma rays is very narrow, making it one of the narrowest gamma storm jets detected by humans. The research team believes that the extremely narrow jet may be one of the reasons why the gamma storm appears extremely bright. Therefore, this observational study of the Insight and Polar Eyes provides a new perspective for a deeper understanding of this extreme cosmic burst phenomenon.

The Huiyan Satellite and Polar Space Telescope were both proposed and led by the Institute of High Energy. The Huiyan Satellite project was proposed by Li Tianbei, Wu Mei, and others in 1993 and was approved for engineering in 2011. Its development has been jointly supported by the civil aerospace scientific research funds of the State Administration of Science, Technology and Industry for National Defense and the Chinese Academy of Sciences' "Space Science" (Phase I) strategic leading science and technology project. The Institute of High Energy Technology is responsible for satellite payloads, ground application systems and scientific research, and the Fifth Academy of Aerospace Science and Technology Corporation is the overall satellite unit. Since its launch on June 15, 2017, the Comet satellite has been in orbit for more than five years and has made a series of important achievements in black holes, neutron star, rapid radio bursts and other fields.

The "Huairou-1" Polar Camera (GECAM) satellite is an opportunity space science project supported by the "Space Science" (Phase II) strategic leading science and technology project of the Chinese Academy of Sciences. The project proposal was put forward by the Institute of High Energy Technology in 2016, and the project was approved in 2018. The third payload (No. GECAM-C) of the Jimu series participated in this discovery, which was launched into orbit on July 27, 2022 with the new space technology test satellite (SATech-01) led by the Institute of Micro Satellite Innovation of the Chinese Academy of Sciences. The Jimu series of satellites have adopted a series of innovative detection technologies and pioneered the use of the Beidou navigation system short message service to achieve quasi real-time communication between the satellite and the ground. A large number of high-energy bursts such as gamma storms, magnetostar bursts, high-energy counterparts of fast radio bursts, solar flares, and Earth gamma flashes have been discovered.

This study has received funding from key research and development programs of the Ministry of Science and Technology, as well as projects such as the National Natural Science Foundation of China.