Convective χ parameter of Foglizzo et al. (2006) for our 3D simulations in both progenitors. Marked as the dashed black line is χ = 3, which Foglizzo et al. suggest is the critical threshold above which conditions are favorable for convection. Successful explosions result in χ > 3 after ~100 ms, while the failed explosions show smaller values of χ that remain below ~3.