Shulou(Shulou.com)11/24 Report--

CTOnews.com, December 11, according to CCTV news, gamma ray bursts (Gamma-ray Burst, also known as GRB) are high-energy rays that occur in distant galaxies. The energy released in one second is equal to the total energy released by the sun for about 5 billion years. It is called the most powerful event in the universe. Chinese scientists proposed this week that a new model of the origin of gamma ray bursts was published in the international academic journal Nature, and the results challenge previous views.

According to the website of the School of Astronomy and Space Science of Nanjing University, the energy released by the sun in a second can be used by human beings for hundreds of thousands of years. Since the birth of the universe, there is a kind of celestial events that can release the sun's lifetime energy in one second. It is the most violent celestial explosion phenomenon-gamma ray bursts.

On December 8, Professor Zhang Binbin of the School of Astronomy and Space Science of Nanjing University led the research team to publish the paper "A long-duration gamma-ray burst with a peculiar origin" in the world's top scientific journal Nature. The team discovered a case of observational gamma-ray burst GRB 211211A, obtained evidence for the association of this long gamma burst with a thousand nova through detailed data analysis, and creatively proposed the special physical origin behind the event, pointing out that its predecessor star may be a neutron star-white dwarf hybrid system.

Gamma-ray burst is a burst phenomenon in which gamma-ray radiation suddenly increases and decays rapidly from the depths of the universe. Since it was first discovered by human beings in 1967, there have been nearly 10,000 observed samples of gamma ray bursts. Through the statistics of these large samples, it is found that the duration of gamma ray bursts ranges from a few milliseconds to thousands of seconds, and its distribution shows a significant bimodal structure with a boundary of two seconds. Therefore, gamma ray bursts are divided into short bursts and long bursts, and their typical durations are about 0.5 seconds and 25 seconds, respectively.

CTOnews.com learned that the physical origin of long and short bursts has always been the focus of debate among astronomers. A paper recently published by Professor Zhang Binbin of Nanjing University in the journal Nature revealed a long gamma ray burst with a special physical origin, further proving the diversity of the origin of gamma bursts.

According to reports, this special gamma burst event is numbered GRB 211211A. What makes it unique is that although it is a long storm, it has a clear connection with a thousand nova. The research team first made a detailed analysis of its instantaneous radiation data and found that its light variation curve consists of a 13-second main burst phase and a 55-second extended radiation phase. Its extended radiation characteristics are obviously different from the previous "tail radiation", showing significant high-energy radiation and the peak energy of the energy spectrum is much higher than that of hard X-rays. This means that it can not be interpreted as an internal short storm through the "iceberg effect" as before, but can only be categorized as a long storm. However, the other instantaneous radiation characteristics, host galaxy characteristics and supernova loss of this gamma burst are not consistent with the characteristics of typical long bursts, but are surprisingly consistent with the height of the short bursts from which compact stars merge. The research team of Professor Zhang Binbin of Nanjing University found the evidence of the existence of thousand nova radiation through multi-band observation data, which determined the merging origin of GRB 211211A. This is the first discovery of a long gamma burst with a compact star merging origin that is much longer than the typical time of a short burst, and it is also the first time that a thousand nova from a long burst has been discovered.

The unique observational features of GRB 211211A challenge scientists' understanding of the precursor star system and central engine model of gamma ray bursts. First of all, the absence of a supernova can directly rule out the possibility that the storm originated from the nuclear collapse of a massive star; second, the duration of the main burst phase exceeds the statistical upper limit of the duration of the short burst (9 seconds). In theory, the central engine accretion time scale provided by neutron star-neutron star / black hole merging is difficult to reach such a long time. The team further pointed out that none of the existing predecessor star models could explain the unique observational characteristics of the storm. Therefore, in order to explain the duration, researchers must propose a new predecessor star model, whose predecessor star system must contain dense celestial bodies whose density is lower than the density of neutron star matter, in order to meet the requirements of the accretion time scale of the central engine to reach tens of seconds. In addition, the system must also produce enough neutron matter to support the generation of thousand novae. Based on the above analysis, it is clear that the new predecessor star system, that is, the white dwarf-neutron star merging system. The team believes that the merging of white dwarfs and neutron stars produces a fast-rotating, highly magnetized neutron star, known as a magnetar. The rotation energy and magnetic energy of magnetars drive 55 seconds of extended radiation and thousands of seconds of X-ray platform radiation, and provide additional energy injection for millennia. The research team proposed this scheme for the first time to explain GRB 211211A and pointed out that it is self-consistent and completely consistent with all the observed characteristics of the storm. Future low-frequency gravitational wave detectors are expected to confirm the existence of this precursor star system.

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