Scheme of the low-τ peak response and the smeared echo for a bowl rim observed at inclination i ≈ 16°. The dust torus is shaded in gray. The bowl rim has been adopted as a “parabola” with exponent α = 2.2, slightly more convex than in Fig. 16. The long dashed lines indicate the isodelay contours. That part of the rim for which the lag matches the data is defined in red; it leads to a sharp low-τ peak response. On the other hand, the entire part of the rim on the left-hand side (marked by the blue arrow) leads to a broad response that is more delayed and smeared out over time.