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 Artistic view of a gamma-ray burst with jet

Artistic view of a gamma-ray burst with jet (©︎ ICRR UTokyo/Naho Wakabayashi)

The MAGIC telescopes were built to observe short-termed violent objects as gamma-ray bursts.

The MAGIC telescopes were built to observe short-termed violent objects as gamma-ray bursts. (Photo: Robert Wagner/MAGIC)

Gamma-ray burst with ultra power

MAGIC telescopes observes most violent gamma-ray burst to date

The gamma-ray burst recorded by the two MAGIC telescopes on 14 January 2019 was spectacular: Never before have astrophysicists captured a gamma-ray burst with such high energy – hundreds of billions times more intense than that of visible light. MAGIC did not capture the gamma-ray burst until the glow (i.e. after its energy became weaker). From this, the scientists concluded that there are physical mechanisms other than those previously assumed at work in the afterglow of gamma-ray bursts.

Thanks to the observation of GRB 190114c, as it is known to astrophysicists, the MAGIC collaboration was able to prove what astrophysicists had suspected for a long time: that gamma-ray bursts in the teraelectronvolt (TeV) range glow in the highest energy range (1).

For around 30 seconds, the afterglow of the gamma-ray burst was over 100 times stronger than the Crab Nebula, the brightest known source in our galaxy. After that, the signal diminished relatively quickly. After just 30 minutes, MAGIC could no longer measure any emissions.

Quickly at the right place

The energy monster was first sighted by the Swift and Fermi satellites. After 22 seconds, the two scouts from the US space agency NASA, alerted a number of different telescopes, including the MAGIC Duo on La Palma, each with a mirror diameter of 17 meters.

Targeting gamma-ray bursts from Earth is a difficult task. “These objects can light up anywhere in the sky at any time – and then quickly disappear again. The MAGIC telescopes therefore feature a fully automated system to process satellite signals”, explains Razmik Mirzoyan, scientist at the Max Planck Institute for Physics and spokesperson for the MAGIC research network.

If a celestial body can be seen from their location, the telescopes can be brought into position extremely quickly with a powerful drive unit. “Despite their weight of 64 tons each, the telescopes can swivel towards new heavenly targets in an extremely short time – with the current gamma-ray burst, it was only 27 seconds after the first alert was issued”, says Mirzoyan.

Only a few hours later, more than two dozen other instruments also began to follow the celestial event. With observations from the radio frequency range through to gamma rays, scientists now have a detailed picture of this gamma burst. Optical telescopes were also used to estimate the distance from GRB190114c: for cosmic scales, the gamma-ray burst occurred “just around the corner”, so to speak, in a galaxy about 4.5 billion light years away.

What drives the energy to record levels?

Even 50 years after their first observation, it is still unclear which physical processes take place during gamma-ray bursts. Some theoretical models had predicted that gamma-ray bursts would emit high-energy photons like these. However, there had been no proof until the current discovery. But what is the mechanism that causes them?

Gamma-ray bursts radiate in different energy ranges. Scientists trace the lower-energy emissions observed to date in the afterglow back to the synchrotron radiation. This occurs when high-energy electrons spiraling through a magnetic field. However, this mechanism is out of the question for the observed record radiation – there must therefore be another motor. One possibility would be the inverse Compton process. In this process, high-energy electrons transfer their energy to photons. The light particles thus reach energy levels in the TeV range.

The current measurement data for different wavelengths (multi-wavelength observations) provide important information in order to decipher the physical processes behind the gamma-ray bursts. In addition, MAGIC scientists have now taken a closer look at earlier gamma-ray burst observations.

They realized that aside from its relative proximity to our solar system, GRB 190114c is not a one-off case. “Our discovery may only be a first indication that all gamma-ray bursts emit radiation at the highest energy level”, says Mirzoyan. “We therefore hope to discover many more gamma-ray bursts with an energy in the teraelectronvolt range so that we can learn more about these fascinating celestial objects.

1) The most energetic radiation in the electromagnetic spectrum consists of gamma rays. The electromagnetic spectrum also includes X-rays, UV light, visible light, and microwaves and radio waves. They have an energy between 100 gigaelectronvolts and 100 teraelectronvolts.