Three articles published in the journal “Nature” report different aspects of the study of a gamma-ray burst cataloged as GRB 190114C which was observed at many frequencies in what’s called multiband observation. Many scientists, particularly the ones from the MAGIC Collaboration, combined observations made using space and ground-based telescopes to study the gamma-ray burst with the greatest energy ever observed. In fact, photons were detected with an energy of the order of the teraelectronvolt, a level theorized for a long time but only now confirmed. A fourth article to be published in the journal “Astronomy and Astrophysics” reports an analysis of the galaxy in which GRB 190114C occurred.
Gamma-ray bursts are extremely intense gamma rays emissions that can last only a few milliseconds but also many minutes. These are the most energetic events observable since the Big Bang is not observable, so extreme events are needed to trigger it.
On January 14, 2019, the Swift and Fermi space telescopes detected a gamma-ray burst of such power that all satellites in orbit sensitive to gamma rays detected it. Different frequencies were detected by other telescopes, a multiband observation that crossed the electromagnetic spectrum reaching the detection of radio waves, on the opposite side of the spectrum with respect to gamma rays, by the MeerKAT radio telescope.
Among the ground instruments that participated in the observations of the GRB 190114C gamma-ray burst range there are the MAGIC (Major Atmospheric Gamma Imaging Cherenkov) telescopes, which can detect high-energy gamma rays even in the order of the teraelectronvolt (TeV) and for this reason made it possible to ascertain that GRB 190114C reached such levels, theorized but not yet detected.
The MAGIC telescopes observed ultra-high-energy photons up to half an hour after the start of the GRB 190114C gamma-ray burst. The afterglow, the glow after the gamma-ray burst, fades over time but a very quick warning sent to various observatories around the world made it possible to conduct many follow-up observations at all frequencies. The observations were helped by the fact that it was a long-duration gamma-ray burst, with an emission lasting more than two seconds, and the afterglow was still detected ten hours later by the H.E.S.S. (High Energy Stereoscopic System) telescope, another instruments capable of detecting gamma rays.
All these observations made it possible to identify the area of space where there’s the source of GRB 190114C at a distance estimated between about 5 and 7 billion light from Earth and to have multiband observation data to examine the processes in progress. Photons at different energies are often emitted from different regions in the area where a gamma-ray burst occurs so the information that can be obtained is different. The MAGIC telescopes were crucial because the photons at the highest energies come from the regions closest to the source of the gamma-ray burst.
The characteristics of the GRB 190114C gamma-ray burst suggest that it may have been generated by the collapse of a massive star. The emission of photons at a teraelectronvolt could be due to the so-called inverse Compton scattering process, in which photons receive energy from electrons that have an even higher energy that were accelerated by the explosion. However, it’s also possible that another mechanism is involved to produce those high-energy photon emissions. The photons emitted during the afterglow, at lower energy, were generated by the synchrotron process, where there’s an interaction between electrons and magnetic fields.
The very high energy of the GRB 190114C gamma-ray burst and its multiband observation offered important information on an extreme event. Increasingly advanced instruments and improvements in worldwide coordination among many observatories will allow further high-quality observations of future gamma-ray bursts to better understand their nature.