Using the H.E.S.S. observatory, researchers at GRB 190829A observe unusual features that challenge models
Researchers from the H.E.S.S. Collaboration succeeded to derive the intrinsic spectrum of the very-high-energy gamma-ray afterglow emission of a relatively nearby gamma-ray burst. Surprisingly, the gamma-ray spectrum resembles that of the much lower-energy X-rays, while the fading emission from both bands was observed to march in parallel over three nights. These remarkable findings challenge the current emission scenarios.
Gamma-ray bursts (GRBs) are bright X-ray and gamma-ray flashes observed in the sky, emitted by distant extragalactic sources. They are associated with the creation or merging of neutron stars or black holes; processes that result in an explosive outburst of the material moving incredibly close to the speed of light. The initial flashes, which last a few seconds, are followed by a long-lived afterglow phase that can be detectable for several days in X-rays, and often weeks or even months in the optical and radio bands. It was this afterglow emission that first confirmed the extragalactic origin of GRBs. The X-ray afterglow radiation is produced by accelerated electrons interacting and losing energy within the blast wave magnetic field. This energy is radiated in the form of synchrotron photons.
