Second new one turned out to be a super-powerful natural particle accelerator

(ORDO NEWS) — The flashes of the new RS Ophiuchus are capable of accelerating cosmic particles to the theoretical limit.

The HESS Gamma-ray Telescope helped observe the 2021 RS Ophiuchi reoccurrence supernova from start to finish, capturing a stream of ultra-high-energy particles that are accelerated by this explosion almost to the theoretical limit.

The work is also described in a press release from the German research center DESY, which manages HESS.

Some stars can flare up sharply and brightly at intervals of several tens of years. These flashes are not as powerful as those of supernovae: the brightness of the star temporarily jumps “only” by ten magnitudes, and the star itself remains intact.

A classic example of such a repeated nova is RS Ophiuchus , which flares up every 15-20 years. Like some other such stars, RS Ophiuchus is a binary system consisting of a red giant and a white dwarf, located at a very short distance, about the same as the Earth and the Sun.

It is believed that its outbursts are associated with the accumulation of matter that the denser dwarf draws from its loose, swollen neighbor. When the mass of this substance becomes sufficient, thermonuclear processes are launched in it, quickly leading to an explosion and a flash.

The brightness of RS Ophiuchi briefly jumps a hundred thousand times higher than that of the Sun. The shock wave created by the explosion propagates in the cloud surrounding the system, collides with its particles and accelerates them, sending them on a long-range flight at great speed.

Some of these particles eventually enter the earth’s atmosphere. Hitting with particles in it, they give rise to a whole shower of short-lived particles, the radiation of which can be observed with the help of Cherenkov gamma-ray telescopes.

This is how the HESS telescopes operating in Namibia tracked the latest outburst of RS Ophiuchus, recorded in August 2021. Thanks to HESS, the authors were able to analyze the outburst from the very beginning until a month after, when the flux of high-energy particles finally dropped.

The work showed that the force of thermonuclear explosions in RS Ophiuchus is converted into the energy of accelerated particles with exceptional efficiency, close to the theoretical limit.

A particle accelerated by this nova can carry more than 100 gigaelectronvolts – hundreds of thousands of times more than other similar systems. The energy of alpha particles ejected by a nuclear explosion is thousands of times lower.

It is curious that the peak of the appearance of the most “energetic” particles in RS Ophiuchus was recorded a couple of days later than the peak of not so powerful particles. Apparently, this is exactly the period needed for the flare to ensure that its shock wave gains full strength.

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