A correct and complete physical description of a neutron star is necessary to make accurate predictions of gravitational waveforms and to connect the emitted gravitational radiation to the physics behind it. Such a description would have to include not only the gravitational behaviour of the star, but also all aspects of its microphysics. Given the extreme densities in neutron stars and the many timescales involved, this is a very complicated theoretical and numerical problem, which is yet unsolved. It touches various fields of physics, such as electroweak interactions, thermodynamics, quantum-chromodynamics. Our research is currently focused on neutrino emission and radiative transfer, which play a very important role in the gamma-ray burst fireball model.