Extragalactic neutrinos on the wings of GRBs
A model published this week in Nature Communications, from the data of IceCube, reconstructs the production process more types of astroparticle by the gamma-ray burst. It shows how the different outcomes are a result of the non-uniformity of their internal structure.
Gamma-ray bursts as intergalactic highways. This analogy was chosen by Mauricio Bustamante, of Ohio State University, to offer an image of their complex internal structure. “Streets full of cars that run, all very fast. But some are normal sports cars, as fast, while others are real racing cars from Formula 1 and clashing along the way are shattered, producing debris.
Credit: NASA/Swift/Mary Pat Hrybyk-Keith and John Jones
Debris that always contains both neutrinos, both cosmic rays, gamma rays is, “says Bustamante out of metaphor,” but only one of the three will dominate the issue. To decide which of the three, will be the point at which we have verified the collision »
The gamma-ray bursts are analyzed by Bustamante and colleagues, after the big bang, is the most violent events in the universe. The emission of these – in the form of two opposing jets of particles, fired at close to the speed of light and, as a result of the magnetic fields, even at extremely collimated intergalactic distances – is associated with the explosion of supernovae. They are detected in space by satellites such as NASA’s Swift telescope. And the “debris” than before, precisely those products from their collisions, they may come to Earth – so at least say scientists – even in the form of cosmic rays and neutrinos.
In particular, according to the model published online today in Nature Communication, if the collision takes place not far from the origin of gamma-ray bursts, where the cars of metaphor highway are more dense, debris will be formed for the most part by neutrinos. Hand in hand, along the path of the beam, the particle density decreases, so here is that collisions give rise more and more often to cosmic rays. Until, moving further away from the starting point, the concentration of the particles becomes very low, this is the stage where the clashes produce gamma rays that we see on Earth.
The reconstruction given by the team led by Bustamante shows as well as several “messengers” – neutrinos, cosmic rays, gamma rays – come from collisions occurred within three different regions of space, determined by their distance from the origin. One hypothesis that has important consequences on the experimental side: thanks to observations “multi-messenger” – not simply multiband, therefore multiple frequency bands, but with instruments capable of detecting, in addition to photons, even cosmic rays and neutrinos – is possible to reconstruct the evolution of the issue of gamma-ray bursts. Tools such as the 86 detectors of IceCube that in 2013, in the depths of the Antarctic ice, caught for the first time two extragalactic neutrinos.
The model published in Nature Communications, indeed, suggests that the rate of production of neutrinos from the gamma-ray burst might be lower than previously thought, and therefore only small part – about one in ten – neutrinos detected on Earth come from the GRB. A flow below the minimum detection threshold of current neutrino telescopes, the researchers say. But if the calculations of Bustamante and colleagues will be corrected, the tools of the next generation – as IceCube-Gen-2 – should be sensitive enough to detect even the minimum flow expected, thus paving the way for a new way to investigate the internal structure of gamma-ray bursts.