Intimate gamma-ray bursts raise new mysteries

Intimate gamma-ray bursts raise new mysteries
Editorial staff
/ idw / DESY News Release
astronews.com
4. June 2021

Through the special telescopes of the HSS Laboratory in Namibia, the most powerful radiation to date was recorded by a gamma flash and followed by a very long period of time in the area of ​​gamma radiation. However, the observations present new mysteries to the team as they seem to contradict a previously desired theory about these events.

Bright bursts in the universe are stronger particle accelerators than expected: this is shown by an unusually detailed observation of such a cosmic flash of gamma rays. Through the special telescopes of the HSS Laboratory in Namibia, an international research team recorded the most powerful radiation from gamma flash to date and followed the longest range of gamma radiation in a long time. Evaluation of the data X-rays and gamma rays of these large star eruptions have the same cause, as they were previously thought, not caused by separate processes.

“Gamma-ray bursts are bright bursts of X-ray and gamma radiation that come from sources outside our own galaxy,” explains Sylvia Xu, a DC researcher who is now one of the authors of the proposed study. “They are the largest eruptions in the universe and are associated with the rapid rotation of a massive star into a black hole.”

A portion of the released gravitational energy drives very fast, intense relative shock waves. In it, the particles are accelerated like electrons, resulting in the formation of gamma radiation. Gamma-ray bursts (GRP for short) are divided into two phases: a short and chaotic burst phase that lasts a few dozen seconds, and a long, slow-disappearing backlight. Both satellites were recorded on August 29, 2019 Fermi And Swift The US space agency NASA has released a gamma-ray flash to the southern galaxy of Eridanus. Event Date Listed as GRB 190829A. About a billion light-years away, it became one of the closest gamma-ray bursts ever seen. By comparison: a typical gamma-ray burst is about 20 billion light years away.

“We actually saw this gamma-ray explode from the front row,” says Dessie researcher Andrew Taylor. The group later recorded the sighting of the HS telescope. “We were able to see a setback for several days and unprecedented energies,” Taylor says. The relatively short distance of the gamma-ray flash enabled detailed measurements of the high energy spectrum of its backlight, i.e. the “color” or energy distribution of the x-ray and gamma photons.

Edna Ruiz-Velasco from the Max Planck Institute for Atomic Physics in Heidelberg said, “The spectrum of the GRP 190829A can be measured up to 3.3 tera – electron volts, which is a trillion times more energetic than visible light.” “This is what makes this gamma-ray burst so extraordinary – it happened in our direct cosmic environment, so that photons with its highest energy are not absorbed by collisions with background light, which happens over long distances in the universe.”

At very high energies, this process makes the universe opaque over long distances. Hess followed after the gamma-ray eruption until the third day after the original eruption. “Our observations reveal a significant similarity between the X-ray component and the later high-energy gamma radiation,” says Xu.

This is surprising because the generally accepted theory assumes that these two radiation components must be generated by different mechanisms: so X-ray radiation comes from strongly accelerated electrons, which are deflected by strong magnetic fields near the explosion. Using this “synchronization process”, particle accelerators on Earth also generate intense X-rays for scientific research.

However, according to current theories, the synchronization process is initially out of the question for the production of very high energy gamma radiation. The so-called burn-off limit is determined by the rate of acceleration and cooling of the particles in an accelerator, which is the offense. The production of gamma radiation requires electrons with energies higher than the burning limit, which cannot actually produce even strong explosions in space.

Instead, the theory assumes that fast electrons collide with already high-energy synchronous photons and elevate them into gamma energies in action. This complex process is called synchronous self-combustion (SSC). However, observations of the backlight of GRP 190829A show that both components – i.e. X-rays and gamma rays – have faded synchronously. In addition, the gamma-ray spectrum goes well with the extension of the X-ray spectrum. Taken together, these properties are a strong indication that the two radiation components are formed by the same process.

Dmitry Gangulyan of the University of Ricoh in Tokyo explains: “We do not expect remarkably similar spectrum of X – ray radiation and transient properties and very high energy gamma radiation.” This calls into question the SSC process as the origin of gamma radiation.

Whether the theory of gamma-ray bursts should be changed can only be clarified by further observations of the very high energy components of their backlight. However, GRP 190829A is only the fourth gamma-ray flash to be detected at these higher energies. However, previously discovered gamma-ray bursts came from a great distance, and their regression could only be seen for a few hours, but not at energies greater than one tera-electron volt (TeV).

“Next generation tools are like that Serenkov Telescope Series, Which is currently under construction in the Chilean Andes and on the Canary Islands of La Palma, has a very promising prospect of following a gamma-ray burst like this, ”said Stephen Wagner, a HES spokesman for the Heidelberg State Laboratory. A lot of energy helps to better understand the physics of these massive cosmic explosions. ”

Hess is a system called the Five Imaging Serenkov Telescopes for the investigation of cosmic gamma rays. The name implies High energy stereoscopic system (Stereoscopic system for observing high energy radiation) and Victor Franz Hess, inventor of cosmic rays, won the 1936 Nobel Prize in Physics. Hess is located in Namibia in the Gasberg region, which is known for its excellent monitoring conditions. Four of the five HS telescopes went into operation in 2003, and the fifth, significantly larger telescope, has been in operation since July 2012.

The group now has a special article in the journal about their observations Science Appeared.