BARYON PURITY IN COSMOLOGICAL GAMMA-RAY BURSTS AS A MANIFESTATION OF EVENT HORIZONS

The mass-loss rate driven by an electron-positron fireball created in the late stages of an accretion-induced collapse or neutron star merging is calculated. It is shown that the solution connecting the wind regime to the hydrostatic regime has a well-defined mass flux in steady state. Approximately 10(31) g s-1 in baryons is found to be injected if the energy deposition rate below the surface of a neutron star is of order 10(32) ergs s-1 cm-3, requiring a powerful suppression mechanism of baryon contamination for cosmological GRB models. It is suggested that the bursts are jets emerging along event horizon-threading field lines, so that the baryons are thereby suppressed, and that cosmological gamma-ray bursts may then represent a qualitative manifestation of the phenomenon of event horizons. The baryonic outflow may represent an r-process site. Ultra-high-energy Galactic cosmic rays may also be produced by shock acceleration within the jet.