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Convective boundary mixing (CBM) in the advanced evolutionary stages ofmassive stars is not well understood. Structural changes caused by convectionhave an impact on the evolution as well as the subsequent supernova, or lackthereof. The effects of convectively driven mixing across convective boundariesduring the post He core burning evolution of $25\mathrm{M}_{\odot}$,solar-metallicity, non-rotating stellar models is studied using the MESAstellar evolution code. CBM is modelled using the exponentially decayingdiffusion coefficient equation, the free parameter of which,$f_{\mathrm{cbm}}$, is varied systematically throughout the course of thestellar model's evolution with values of $(0.002, 0.012, 0.022, 0.032)$. Theeffect 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 percentdifferences from the model with minimal CBM as large as 86.3%. At thepresupernova stage, the compactness of the stellar cores from O'Connor & Ott(2011), $\xi_M$, exhibit a range of $(0.120, 0.354)$, suggesting that theextent of CBM in the advanced burning stages of massive stars is an importantconsideration for the explodability and type of compact remnant. Thenucleosynthetic yields from the models, most notably C, O, Ne, Mg and Si arealso significantly affected by the CBM assumptions, showing non-linear trendswith increased mixing. The simulations show that interactions betweenconvective C, Ne and O shells produce significant non-linear changes in theevolution, whereas from the end of Si burning, the structural changesattributed 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 DOIto appear).

Convective boundary mixing in a post-He core burning massive star model