Gamma ray bursts (GRBs) are rare and only occur when extremely massive stars go supernova. The stars’ strong magnetic fields channel most of the explosion’s energy into two powerful plasma jets, one at each magnetic pole. The jets spray energetic particles at light speed for light-years in both directions.On the Earth, we detect bits of the resulting debris as gamma rays. The amount of debris that reaches the Earth depends on how energetic the star is and how far away it is.
Researchers suspect that GRBs are the source of at least some of the cosmic rays and neutrinos that pepper our planet from space.By building some of the most detailed computer simulations ever made of a GRB jet’s internal structure, physicists at the Ohio State University and their colleagues have been able to model particle production inside of it.
Mauricio Bustamante, a Fellow of the Center for Cosmology and AstroParticle Physics at Ohio State, explained that the new computer model is a natural outgrowth of recent findings in astroparticle physics, such as the first confirmed cosmic neutrinos detected at the IceCube Neutrino Observatory at the South Pole in 2013.
“Previously, the details of the non-uniformity of the GRB jets were not too important in our models, and that was a totally valid assumption–up until IceCube saw the first cosmic neutrinos a couple of years ago,” he said. “Now that we have seen them, we can start excluding some of our initial predictions, and we decided to go one step further and do this more complex analysis.”
With partners at Penn State and the DESY national research center in Germany, Bustamante wrote new computer code to take into account the shock waves that are likely to occur within the jets. They simulated what would happen when blobs of plasma in the jets collided, and calculated the particle production in each region.In their model, some regions of the jet are denser than others, and some plasma blobs travel faster than others.