Causal solutions for radiating stellar collapse

Recently, Govender et al. (Class. Quantum Grav. 15 (1998) 323) presented a simple model of radiating stellar collapse with a shear-free and non-accele rating interior matched to a Vaidya exterior. While highly simplified, this model did allow some insight into the temperature profile of the star duri ng its evolution. However, the only exact causal solution for the temperatu re presented was in the case of constant mean collision time (sigma = 0) (w ith perturbative results for small sigma). We present two new exact causal solutions for the temperature equation and discuss the resulting temperatur e profiles of the collapsing star. We also provide similar results for the case of non-zero acceleration. In addition we provide non-constant mean col lision time temperature solutions for the most general shearing line elemen t with spherical symmetry. (C) 2001 Elsevier Science B.V. All rights reserv ed.