The presence of unusually energetic gamma rays seen in some afterglows from intense gamma-ray bursts (GRBs) could be explained by a new mathematical model developed by RIKEN researchers. This finding could help to shed light on the origin of GRBs.
A GRB is a spectacular eruption of energy produced by violent events such as the explosive death of a massive star or the collision of two neutron stars. A GRB also shoots a jet of matter and energy into the material that surrounded the star. Shocking particles such as protons and electrons cause them to emit radiation. The emitted photons can be detected from Earth as a GRB afterglow.
The vast majority of GRB afterglow observations can be explained by current theories. This should come as no surprise. They would not be the current theories if they didn’t match reality. But the afterglows of two recent GRBs produced gamma rays with unusually high energies that strain these theories.
Scientists compared two theoretical models of afterglows, to explain the unusual gamma rays. The first was based on conventional theory, suggesting that the distribution of energy among the shocked electrons follows a fairly simple curve. It is known as a power law distribution. Most electrons have relatively little energy and only a few have the highest energies, in this scenario. It’s important to keep a sense of perspective though.
Their second model added some so-called thermal electrons into the mix. These have a different energy distribution. It resembles the way that molecules in a hot gas share out their energy.
The second model features more electrons at just the right energy to generate the high-energy gamma rays seen in the afterglows of the two highly energetic GRBs.
That means the second model potentially offers a better description of these GRB afterglows. This could ultimately help astronomers to refine their theories about how GRBs themselves occur.
