Gamma Ray Bursts via emission of axion-like particles

Abstract

The Pseudo-Goldstone Boson (PGB) emission could provide a very efficient mechanism for explaining the cosmic Gamma Ray Bursts (GRBs). The PGBs could be produced during the merging of two compact objects like two neutron stars or neutron star - black hole, and then decay into electron-positron pairs and photons at distances ~ 100-1000 km. In this way, a huge energy (up to more than 10^{54} erg) can be deposited into the outer space with low baryon density in the form of ultrarelativistic e^+e^- plasma, the so called fireball, which originates the observed gamma-ray bursts. The needed ranges for the PGB parameters are: mass of order MeV, coupling to nucleons g_{aN} ~ few x 10^{-6} and to electrons g_{ae} ~ few x 10^{-9}. Interestingly enough, the range for coupling constants correspond to that of the invisible axion with the Peccei-Quinn symmetry breaking scale V ~ few x 10^5 GeV, but the mass of the PGB is many orders of magnitude larger than what such a scale would demand to an axion. Neither present experimental data nor astrophysical and cosmological arguments can exclude such an ultramassive axion, however the relevant parameters' window is within the reach of future experiments. Another exciting point is that our mechanism could explain the association of some GRBs with supernovae type Ib/c, as far as their progenitor stars have a radius ~ 10^4 km. And finally, it also could help the supernova type II explosion: PGBs emitted from the core of the collapsing star and decaying in the outer shells would deposit a kinetic energy of the order of 10^{51} erg. In this way, emission of such an axion-like particle could provide an unique theoretical base for understanding the gamma ray bursts and supernova explosions.