Close-up gamma-ray does not match the flash image

Strong eruptions of the cosmos – brief bursts of high-energy gamma radiation – remain a mystery to astronomers: the gamma and X-ray radiation emitted by such a gamma-ray flash is relatively low – in contrast to the previous theoretical model. Observations now indicate that both gamma and X-rays have the same cause, according to scientists from the International HSS Collaboration in the journal Science.

“Gamma-ray bursts are gamma and X-ray bursts that come from sources outside our Milky Way,” explains Sylvia Ju of the DC Research Center involved in the study. “They are associated with the fall of a large star into the black hole.” A portion of the energy released in this process drives a shock wave, which propagates at the speed of light and accelerates electrons. Approximately light-speed electrons then produce an explosion of high-energy radiation that lasts only a few seconds: a gamma-ray flash.

NASA’s Fermi and Swift satellites recorded such a gamma-ray burst on August 29, 2019. At a distance of about one billion light-years from Earth, it became unusually close – most of the radiation from gamma-ray bursts, on the other hand, takes an average of ten billion years to reach us. Significantly shorter distances enabled researchers to analyze in detail the aftermath of a gamma-ray eruption, i.e. the X-ray and gamma rays deformed after the eruption.

With special telescopes of the HS High Energy Stereoscopic System in Namibia, astronomers were able to observe unusually long after-light – up to three days before the actual eruption. “Observations revealed a striking resemblance between the X-ray component and the later high-energy gamma radiation,” says Xu. This is surprising to researchers as it was previously thought that gamma and X-rays were created differently: according to an earlier theory, X-rays initially occur when the strong magnetic field of the created black hole rapidly deflects electrons. . When these are combined with X-rays, it is assumed that more powerful gamma radiation is generated.

This model now seems questionable. Not only do gamma and X-rays weaken simultaneously after radiation eruption, but the spectrum of gamma radiation is seamlessly connected to X-rays. Dmitry Gangulyan, a researcher at the University of Rico in Tokyo, said: “We do not expect such spectral and temporal properties given the unique appearance of these radioactive elements.

Further observations are now needed to discover the physical processes responsible for the formation of high energy radiation. The eruption of August 29, 2019 in particular was very close to us, so it is the only one that can be seen later with so much time and up to a higher energy limit. As telescopic systems already under construction, such as the Chilean Andes and the Serenkov Telescope Series CDA, are being built in La Palma, the regression of significantly further distant gamma-ray flashes can soon be observed.