According to Institute of High Energy, Chinese Academy of Sciences, at 21:17 on October 9, 2022 (Beijing time), the high-altitude cosmic ray observation station (LHAASO, cable), high-energy burst explorer (HEBS) and Intelligent Eye Satellite (Insight-HXMT) simultaneously detected the brightest gamma-ray burst (number GRB 221009A). Thanks to the rapid development of high-energy in the construction of integrated observation capabilities in the world in recent years, especially the successful construction and operation of LHAASO, it has occupied an international leading position, allowing my country to achieve multi-mean joint observation of gamma ray bursts for the first time, and exclusively achieved multi-spectral fine measurements from the highest dozen dimensional electron volt photons (LHAASO) to megaelectron volt gamma rays (HEBS) and thousand electron volt X-rays (science eyes), spanning 9 orders of magnitude. In this observation, LHAASO increased the maximum energy record of gamma ray exposure photons by nearly 20 times, and opened the gamma ray burst observation window in the 10 TeV band for the first time in the international arena. Together with the Huiyan Satellite and HEBS observations, found that this event was more than 10 times brighter than the brightest gamma ray observed in previous humans. These observations have broken the records of multiple gamma ray burst observations and are of great value for revealing the burst mechanism of gamma ray bursts.
Figure 1: The position of GRB 221009A burst moment in the LHAASO field of view
Figure 2: The brightest gamma ray burst to date observed by the smart eye satellite (GRB 221009A). Before and after the gamma ray burst, the Eye satellite happened to scan and observe the celestial area. The green dot line represents the scanning trajectory pointed by the telescope
Gamma ray burst is the most violent celestial explosion phenomenon in the universe and was first discovered in the 1960s. Gamma ray bursts are as short as a few milliseconds and for hours, releasing more energy than the sum of the sun's radiated energy in its lifetime. Gamma ray bursts with longer durations occur when the collapse explosion of star bodies dozens of times larger than the sun, while gamma ray bursts with shorter durations occur when two dense celestial bodies (such as black holes or neutron star ) merge and explode, which may also be accompanied by gravitational waves emitted. This high-intensity explosion occurred more than 2,000 mega-light years from the earth. Gamma-ray bursts at such a close distance are estimated to occur once every decades or even a hundred years.
Among the thousands of gamma-ray bursts detected in the past half-century, the highest energy photon has reached about 1 trillion electron volts (TeV). This time, LHAASO detected a large number of high-energy photons with an unparalleled reception, with the highest photon energy reaching 18 TeV. The detection results of LHAASO have triggered huge international responses, and a large number of related research has been rapidly unfolding, and many discussions on the possibilities of new physics have emerged. At the same time, these measurements will strongly limit the basic physical parameters and models such as background light fields present in the universe, and are expected to produce important improvements in cognitive levels.
LHAASO records tens of thousands of photon signals in a very high energy area above 100 GeV, and will give the most detailed measurement of the optical change curve of the highest energy segment of the gamma ray burst. With the advanced detector design, HEBS successfully conducted high-precision observations of the soft gamma ray light-changing characteristics of this gamma ray burst, perfectly demonstrating the evolution process of initial bursts and subsequent flashes. The high-energy, medium-energy and low-energy X-ray telescope of the Intelligent Eye satellite detected the signal simultaneously in gamma-ray burst observation for the first time. Moreover, because the Intelligent Eye satellite was scanning and observing this celestial area at the time, it promptly monitored the afterglow of the gamma-ray burst. These measurements with a 1 billion-fold difference in energy are extremely important for establishing a correct model of gamma-ray burst mechanism.
After the gamma ray burst occurred, the team of the LHAASO Experimental Institute of High Energy quickly carried out data analysis under the leadership of the chief scientist Researcher Cao Zhen, and released preliminary observation results to international peers through the Gamma-ray Coordinates Network (GCN) within less than two days after the outbreak. Further data analysis and scientific research are being carried out by members of the LHAASO cooperation group. The High Energy Institute's Huiyan Satellite and HEBS observation and operation team, payload team and data analysis team, led by the Chief Scientist of Huiyan Satellite, Zhang Shuangnan Researcher and Xiong Shaolin, the chief scientist of the HEBS project, quickly invested in observation and analysis, and promptly launched opportunity observation.With the close cooperation of the team, Huiyan Satellite and HEBS have obtained preliminary analysis results and have been released to international peers through Astronomer’s Telegram and GCN.
LHAASO is a major national scientific and technological infrastructure with cosmic ray observation and research as the core. It was independently proposed and designed and built by my country. The observation station is located in Haizishan at an altitude of 4410 meters in Daocheng County, Sichuan Province, covering an area of about 1.36 square kilometers. The main project of LHAASO was completed and put into scientific operation in July 2021. It is the world's most sensitive ultra-high energy gamma ray observatory. The operation of LHAASO has ushered in the observation era of "ultra-high energy gamma astronomy". Capturing and high-statistic observation of gamma-ray bursts is one of the important scientific goals of LHAASO. This unprecedented burst of brightness happened to be near the center of the LHAASO field of view, laying a strong observational foundation for achieving this scientific goal. The Huiyan Satellite is my country's first space X-ray astronomical satellite. It was launched and operated on June 15, 2017. Over the past five years of in-orbit observation, it has achieved a large number of important original results in black holes, neutron stars, fast radio bursts, etc. The High Energy Outbreak Explorer (HEBS) was launched on July 27, 2022. It is one of the main scientific payloads of the new space technology test of satellite recently launched by my country. It uses the new detection technology pioneered by the "Huairou One" satellite and a quasi-real-time satellite-ground communication solution based on Beidou short messages to quickly upload observation data. HEBS is currently in the on-orbit testing phase and is expected to achieve more important results.
