Surface Quantum Effects in a Fireball Model of Gamma Ray Bursts

Recent rapid advances in the observations of Gamma Ray Bursts (GRBs) lend much confidence to the cosmological fireball (FB) model: there is now compelling evidence that the radiation is emitted by a relativistic shock where a high speed upstream flow terminates. The question concerning what generates such an outflow is central to our search for the ultimate trigger mechanism. A key requirement, not well explained by current theories, is that the flow must have high entropy-to-baryon ratio. In this Letter we point out that a quantum discharge induced by the radiation of the initial FB may be the explanation. The effect is likely to be relevant, because the FB energy density inferred from GRB data is large enough that the radiation pressure leads to the formation of a surface electric field which is unstable to pair creation. Under suitable conditions, such as those of a supernova core, the discharge can convert a substantial fraction of the FB energy into surface pairs. This pair plasma is not contaminated by FB baryons because it is formed outside the FB. We demonstrate that the pairs can then develop relativistic bulk expansion, reaching a maximum speed that meets the constraints required to form a GRB.