Absolute values of the normalised torques for planets undergoing outward migration in low-viscosity discs (α = 10⁻⁴) with 2 × 10⁻³ < q < 2 × 10⁻² and e < 0.2 (see Table 1). Left: results from the simulations assuming a local density Σ₀ > 10⁻⁵. Right: results from the simulations assuming Σ₀ < 10⁻⁵. In each panel, the fitting function proposed in this work (dashed red lines-see Eq. (6)) along with a region within ±2 the standard deviation of the logarithmic residuals (red shadow area). Symbols and colours are as in Figure 3.