Today two Nature papers appeared on the detection of a gamma-ray bursts in the 100 GeV domain, observed by MAGIC and HESS.
After a decade-long search, scientist have for the first time detected a gamma-ray burst in very-high energy gamma light, discovered by the H.E.S.S. collaboration in July 2018. This gamma-ray burst, an extremely energetic flash following a cosmological cataclysm, was found to emit very-high-energy gamma-rays long after the initial explosion. Extremely energetic cosmic explosions generate gamma-ray bursts, typically lasting for only a few tens of seconds. They are the most luminous explosions in the universe, The burst is followed by a longer lasting afterglow mostly in the optical and X-ray spectral regions whose intensity decreases rapidly. The prompt high energy gamma-ray emission is mostly composed of photons several hundred-thousands to millions of times more energetic than visible light, that can only be observed by satellite-based instruments. Whilst these space-borne observatories have detected a few photons with even higher energies, the question if very-high-energy gamma radiation is emitted, has remained unanswered until now.
GRAPPA member, Jacco Vink, is one of the co-authors on the H.E.S.S. paper. He calls it a great success, which testifies to the power of these type of gamma-ray telescopes for finding distant explosions. A big surprise was, according to him, that the emission was picked up so long after the initial explosion occurred.