Figure 13.

The asymmetry of eclipses given by the proxy Δf_E for the B1957+20 system due to orbital sweep-back of a parallel-wind shock, as a function of injected velocity, with a_wind = 0, at the companion and shock length L_z = |R(θ) cos θ| downstream from the companion to a maximum of 4–5R₀. The white region corresponds to the portion of the parameter space not allowed by the radio results of Ryba & Taylor (1991); here either the asymmetry of eclipses or the total eclipse fraction are too large even at the lowest frequencies. The orbital speed of the companion is shown as the blue line and varies with inclination due to observed pulsar mass function for a fixed mass ratio q = 69.2. Larger speeds or shorter tails reduce total eclipse asymmetry. Horizontal cuts at a fixed v_inj in the figure may be interpreted as the frequency dependence of the eclipse asymmetry, with lower frequencies sampling larger L_z.