New insights into the optical afterglow of gamma-ray bursts

Scientists from the United Arab Emirates, Britain, the U.S. and Japan have uncovered insights into perhaps the most luminous event known to occur in the universe: the gamma-ray burst. The very nature of these cosmic events are mind bending for astronomers and challenging to simulate in supercomputers. 

The team looked into how the bright afterglows of these cosmic light shows are formed. The authors speculate that the gamma-ray bursts are created when a black hole is formed, releasing large amounts of energy in a shockwave, which is visible as a so-called afterglow. In these shockwaves, electrons are accelerated to high energies. 

Current theoretical models had suggested that the light emitted by these electrons should have no measurable circular polarisation, in which the light waves have a preferred plane of vibration that rotates rapidly. However, the scientists unexpectedly found the contrary, detecting high levels of circular polarisation. 

According to the study, the gamma-ray burst, designated GRB 121024A, was a very ordinary burst, which is what led the scientists to believe that circular polarisation may be a common characteristic in other bursts. Lead author, Klaas Wiersema of the University of Leicester, explains: “It is always very exciting when observations are so directly at odds with theoretical predictions, it opens up completely new avenues of research.”