Stellar luminosity (L) versus effective temperature (T_eff) of a binary from the simulated grids with an initial companion mass of 4.5 M_⊙, initial NS mass of 2.0 M_⊙, and initial orbital period of 1.4 d for different maximum opacity values (κ_max). The solid blue curve is the failed binary. The solid green, dashed red, and dashed purple curves are with κ_max value of 10.0, 5.0, and 0.5, respectively. We compare the tracks to a neighboring track (without any numerical instability) in solid orange.