Alexander J Hackett (Univ. Cambridge)

Thorne- Żytkow Objects (TŻO) are a class of hybrid stars, originally proposed by Thorne & Żytkow (1977), consisting of a neutron star core, surrounded by a diffuse giant envelope. This is analogous to how one may consider the structure of a giant with a degenerate core as a white dwarf embedded in a giant envelope.
Structural and nucleosynthetic models of these objects have not been updated since the models of Cannon et al. 1992/93, all of which are derived from the models of TŻ. Although these models have been shown to be self-consistent, it would be instructive to re-create these models using the mesa stellar evolution
code, without using the models of TŻ a priori.
Using a set of central boundary conditions to mimic the presence of a neutron star, we construct a preliminary series of envelope models that may show some marked differences from those models. Our models’ structures show an expanded analogue of the supergiant-like solutions from TŻ and Cannon et al.
etc, with these solutions being found in a wide range of envelope masses, including in the region where TŻ found a different, giant-like structure.
We discuss our solutions and the implications of the possible existence a parallel series of equilibrium structures for TŻOs. We also discuss the important implications of our structure solutions for possible nucleosynthetic pathways in our models, and the further effects of this on yields of these post-XRB systems,
and on Galactic Chemical Evolution as a whole.