9 - Gravitational collapse versus thermonuclear explosion of degenerate stellar cores

Summary

Abstract

In this paper we review the behavior of growing stellar degenerate cores. It is shown that ONeMg white dwarfs and cold CO white dwarfs can collapse to form a neutron star. This collapse is completely silent since the total amount of radioactive elements that are expelled is very small and a burst of γ-rays is never produced. In the case of an explosion (always carbon-oxygen cores), the outcome fits quite well the observed properties of Type la supernovae. Nevertheless, the light curves and the velocities measured at maximum are very homogeneous and the diversity introduced by igniting at different densities is not enough to account for the most extreme cases observed. It is also shown that a promising way out of this problem could be the He-induced detonation of white dwarfs with different masses. Finally, we outline that the location of the border line which separetes explosion from collapse strongly depends on the input physics adopted.

Dans cet article on revise le comportement d'un noyau stellaire dégénéré qui grandit. On montre que les naines blanches d'ONeMg et celles de CO, froides et massives, peuvent s'effondrer pour former une étoile à neutrons. Cet effondrement est complètement silencieux puisque la quantité tot ale d'élements radioactifs expulsée est très petite et on ne produit pas d'eruption de rayons gamma. Dans le cas d'une explosion (toujours pour des noyaux de carbone-oxygène), le résultat des calculs reproduit assez bien les propriétés observées des supernovae de Type Ia.