Translartion. Region: Russians Fedetion –
Source: State University Higher School of Economics – State University Higher School of Economics –
A team of scientists from 17 countries, including physicists from the National Research University Higher School of Economics, analyzed new photometric and spectroscopic data from the brightest gamma-ray burst in the history of observations — GRB 221009A. They were obtained at the Sayan Observatory 1 hour and 15 minutes after its registration. The researchers recorded photons with an energy of 18 teraelectronvolts. Theoretically, such high-energy particles should not reach Earth, but data analysis showed that this is possible. The results call into question theories of gamma-ray absorption and may indicate unknown physical processes. Study published in the journal Astronomy
Gamma-ray bursts are powerful cosmic explosions that release enormous amounts of energy. They were first detected in the gamma range, which is where they got their name. These bursts occur when massive stars die or neutron stars collide.
On October 9, 2022, several space gamma-ray observatories recorded an unusually bright flash in the gamma-ray range, which was later classified as gamma-ray burst GRB 221009A – the most powerful in the history of observations. The intensity of the burst was so high that it caused malfunctions in the gamma-ray telescopes of most orbital observatories, including Fermi, INTEGRAL, Konus-Wind. In addition, the gamma-ray flux that fell on Earth caused a strong disturbance in the ionosphere.
The energy of GRB 221009A’s radiation in just a hundred seconds was equivalent to the radiation of 1 billion Suns over 97 billion years, despite the fact that the Universe is only 13.8 billion years old. Such events happen extremely rarely – once every thousand years. But it was not only the brightness that made GRB 221009A unique. It was located at a distance of 2.4 billion light years, which is relatively close by the standards of the Universe. For comparison: the most distant known burst was recorded at a distance of about 13.2 billion light years. Therefore, the event aroused interest in the scientific community: already in 2022, 7 articles were published, and by now – more than 200.
Researchers continue to analyze data on GRB 221009A. An international team of scientists from 17 countries, including a team from the National Research University Higher School of Economics, analyzed for the first time the data from photometric and spectroscopic observations obtained at the Sayan Observatory 1 hour and 15 minutes after the gamma-ray burst was registered.
Photometric and spectroscopic observations are methods for measuring the intensity of electromagnetic radiation in the visible and infrared ranges and its “color composition” (spectrum). The former allows us to determine how bright an object was, and the latter – what chemical elements are present in the emitting object and on the path of the radiation to the observer.
The scientists say the data points to sustained activity from the central engine, the compact, massive object that generates the gamma-ray burst. They also note that the environment around the blast changed from denser, shaped by stellar winds, to thinner, more interstellar-like.
Of particular interest to the researchers were the 18-teraelectronvolt (TeV) photons detected by the LHAASO high-altitude observatory from GRB 221009A. Theoretically, such high-energy photons should not be detected due to their interaction with optical photons in the intergalactic medium on their way to the observer, but somehow they still reached Earth. Analysis showed that the detection of 18-TeV photons is unlikely for existing models of the intergalactic background radiation. The detection of such photons from gamma-ray burst sources is still a unique event.
“Registration of high-energy photons allows us to test fundamental laws of physics, such as, for example, the constancy of the speed of light. However, there is nothing to worry about yet, since the effect of registering such high-energy photons can still be explained by the uncertainty of the model of intergalactic background radiation, and not by a violation of Lorentz invariance – a fundamental principle according to which the speed of light is constant in all reference frames,” comments Sergey Belkin, a postgraduate student. Basic Department of Space Physics of the Space Research Institute of the Russian Academy of Sciences Faculty of Physics HSE.
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