Thermal evolution of radiation spheres undergoing dissipative gravitational collapse.

Abstract

In this study we investigate the physics of a relativistic radiating star undergoing dissipative collapse in the form of a radial heat flux. Our treatment clearly demonstrates how the presence of shear affects the collapse process; we are in a position to contrast the physical features of the collapsing sphere in the presence of shear with the shear-free case. We first consider a particular exact solution found by Thirukkanesh et al [1] which is expanding, accelerating and shearing. By employing a causal heat transport equation of the Maxwell-Cattaneo form we show that the shear leads to an enhancement of the core stellar temperature thus emphasizing that relaxational effects cannot be ignored when the star leaves hydrostatic equilibrium. We also employ a perturbative scheme to study the evolution of a spherically symmetric stellar body undergoing gravitational collapse. The Bowers and Liang [2] static model is perturbed, and its subsequent dynamical collapse is studied in the linear perturbative regime. We find that anisotropic effects brought about by the differences in the radial and tangential pressures enhance the perturbations to the temperature, and that causal and non–causal cases yield identical profiles.