Gamma ray bursts from superconducting cosmic strings

Cusps of superconducting strings can serve as GRB engines. A powerful beamed pulse of electromagnetic radiation from a cusp produces a jet of accelerated particles, whose propagation is terminated by the shock responsible for GRB. A single free parameter, the string scale of symmetry breaking $\eta \sim 10^{14} GeV$, together with reasonable assumptions about the magnitude of cosmic magnetic fields and the fraction of volume that they occupy, explains the GRB rate, duration and fluence, as well as the observed ranges of these quantities. The wiggles on the string can drive the short-time structures of GRB. This model predicts that GRBs are accompanied by strong bursts of gravitational radiation which should be detectable by LIGO, VIRGO and LISA detectors. Another prediction is the diffuse X- and gamma-ray radiation at 8 MeV - 100 GeV with a spectrum and flux comparable to the observed. The weakness of the model is the prediction of too low rate of GRBs from galaxies, as compared with observations. This suggests that either the capture rate of string loops by galaxies is underestimated in our model, or that GRBs from cusps are responsible for only a subset of the observed GRBs not associated with galaxies.Comment: 29 pages, Revtex. This is a substantially expanded and revised version of our earlier paper astro-ph/0001213. Final version, to appear in Phys. Rev.