Gammaless GRBs?

The Compactness Problem in GRBs has been resolved by invoking the Lorentz factors associated with the relativistic bulk motion. This scenario applies to GRBs where sufficient energy is converted to accelerate the ejected matter to relativistic speeds. In some situations this may not be a possible mechanism. Hence the gamma rays are trapped in the region. Here we look at these possible scenarios, where the neutrino pair production process dominates, and the neutrinos are able to escape freely. This could give a scenario where release of neutrinos precedes the gamma ray emission, which is much attenuated, possibly explaining why fewer GRBs are observed than what is expected.