Catastrophic disruption criterion for same-mass collisions ($${\mathcal{Q}}_{\mathrm{R}\mathrm{D},\gamma =1}^{\ast }$$) with respect to the combined radius (R_C1) shown on top. The value $${\mathcal{Q}}_{\mathrm{R}\mathrm{D},\gamma =1}^{\ast }$$ is obtained from Eq. (2) by dividing $${\mathcal{Q}}_{\mathrm{R}\mathrm{D}}^{\ast }$$ by the γ-dependent component $${[(1+\gamma {)}^2/4\gamma ]}^{2/(3\overline{\mu })-1}$$. The catastrophic disruption criterion for same-mass collisions scaled by the combined radius squared ($${\mathcal{Q}}_{\mathrm{R}\mathrm{D}}^{\ast }$$) with respect to the mass ratio (γ) are shown at the bottom. The symbols are the same as in Fig. 1. The colours denote the mass ratio γ in the plot at the top, and the combined radius R_C1 in the plot at the bottom. The solid red line corresponds to the best fit from this work, i.e. c^* = 2.661 and $$\overline{\mu }$$ = 0.4797, while the dotted black line corresponds to the best fit from LS12, i.e. c^* = 1.9 and $$\overline{\mu }$$ = 0.36. The binding energy (dashed black line) is shown for reference in the top panel.