  Convective boundary mixing (CBM) in the advanced evolutionary stages of
massive stars is not well understood. Structural changes caused by convection
have an impact on the evolution as well as the subsequent supernova, or lack
thereof. The effects of convectively driven mixing across convective boundaries
during the post He core burning evolution of $25\mathrm{M}_{\odot}$,
solar-metallicity, non-rotating stellar models is studied using the MESA
stellar evolution code. CBM is modelled using the exponentially decaying
diffusion coefficient equation, the free parameter of which,
$f_{\mathrm{cbm}}$, is varied systematically throughout the course of the
stellar model's evolution with values of $(0.002, 0.012, 0.022, 0.032)$. The
effect of varying this parameter produces mass ranges at collapse in the ONe,
Si, Fe cores of $(1.82\mathrm{M}_{\odot}, 4.36\mathrm{M}_{\odot})$,
$(1.67\mathrm{M}_{\odot}, 1.99\mathrm{M}_{\odot})$ and
$(1.46\mathrm{M}_{\odot}, 1.70\mathrm{M}_{\odot})$ respectively, with percent
differences from the model with minimal CBM as large as 86.3%. At the
presupernova stage, the compactness of the stellar cores from O'Connor & Ott
(2011), $\xi_M$, exhibit a range of $(0.120, 0.354)$, suggesting that the
extent of CBM in the advanced burning stages of massive stars is an important
consideration for the explodability and type of compact remnant. The
nucleosynthetic yields from the models, most notably C, O, Ne, Mg and Si are
also significantly affected by the CBM assumptions, showing non-linear trends
with increased mixing. The simulations show that interactions between
convective C, Ne and O shells produce significant non-linear changes in the
evolution, whereas from the end of Si burning, the structural changes
attributed to the CBM are dominated by the growth of the convective C shell.
Progenitor structures for all the models are available from HERE (link and DOI
to appear).
