Nucleosynthesis in tidally disrupted white dwarfs

点击翻译按钮获取中文摘要

Two classes of black holes are established beyond reasonable doubt: supermassive black holes that lurk in centres of galaxies and stellar-mass black holes that are detectable via their interaction with normal stars in X-ray binary systems. Suggestive evidence has accumulated that a third class of so-called intermediate mass black holes (IMBHs) may exist in some globular clusters. As stars drift through the cluster, some will inevitably wander sufficiently close to the hole that they suffer a tidal disruption. IMBHs have the potential to disrupt not only solar-type stars but also compact white dwarf stars which would be swallowed as a whole by more massive black holes. We have recently begun to investigate the fate of white dwarfs that approach the hole close enough to be disrupted and compressed to such an extent that explosive nuclear burning is triggered in some cases. We found that thermonuclear ignition is a natural outcome for white dwarfs provided that they penetrate deeply enough into the tidal radius. Our simulations used a minimal nuclear reaction network coupled to the hydrodynamics. It is tailored to accurately reproduce the correct energetic feedback onto the gas flow, but it cannot deliver detailed isotopic abundances. The calculation of the detailed abundances for such tidal disruptions and their mixing with the cluster are the focus of this proposal.