Speaker
Prof.
Falk Herwig
(University of Victoria)
Description
Both 1D stellar evolution models and 3D hydrodynamic simulations suggest that convective shells in evolved massive stars can interact and sometimes even merge. As a first step towards a 3D simulation of an O-C shell merger, we have investigated the dynamic response of the convective flow in the O shell to the burning of C assumed to be present in the fluid entrained from an overlying stable layer. When the flow is driven by a realistic O-burning profile the entrainment rate is of order 10^(-7) M_Sun/s. A stationary convective-reactive state is reached with C burning providing ~16% of the shell's total luminosity. We experiment with scaling up the driving luminosity to obtain higher entrainment rates that could be realised in a full-blown merger of convective O- and C-burning shells. Nucleosynthesis calculations performed by Ritter et al. (2016) using an effective diffusion coefficient from the 3D simulations show that the burning of Ne present in the entrained material leads to the production of Cl, K, and Sc if the entrainment rate is large enough. Assuming that some fraction of massive stars experience such shell mergers, our simple Galactic chemical evolution model can resolve the long-standing discrepancy between theoretical models and measured abundances of these elements in the Milky Way.
Primary author
Dr
Robert Andrassy
(University of Victoria)
Co-authors
Dr
Benoit Cote
(Michigan State University / University of Victoria)
Mr
Christian Ritter
(University of Victoria)
Prof.
Falk Herwig
(University of Victoria)
Prof.
Paul Woodward
(University of Minnesota)
Dr
Sam Jones
(HITS)