Top: maps of radius residuals (r(ϕ′) − R₁) for e = 0.8, P = 15 d, β₀ = 1.2 at periastron (left) and 0.833 days after (right). The sub-binary longitude (ϕ′ = 0) is at the far left on each map and ϕ′ = 180° is at the center. The sense of the stellar rotation is from left-to-right. White/black represents maximum/minimum residuals. Bottom: corresponding plots of the radius residuals along the equator.