Corner plot showing the posterior PDFs of model M2 in which we adopt different SFEs for the high-α and low-α sequences: ν₁ = 2 Gyr⁻¹ and ν₂ = 1 Gyr⁻¹. The best fit of the 4D parameter space Θ = {τ₁,  τ₂,  t_max,  σ₂/σ₁} is obtained by fitting [α/Fe], [Fe/H] and ages of the APOKASC sample (see model details in Sect. 5.1). The median, 16th and 84^th percentiles of the posterior PDF are plotted for each parameter above the marginalised PDF.