Figure 12.

The effect of constant velocity and acceleration on the parallel-wind swept-back shock tail, out to unity semi-major distance a, in the PSR B1957+20 system due to orbital motion and Coriolis effects. The system angular momentum vector direction is pointing out of the plane in the top two panels, i.e. the system is rotating counterclockwise. The depicted orbital phase is at eclipse egress. For all panels, the dark green coloring mimics the loci of points corresponding to the contact discontinuity injected supersonically at velocity v_inj = 10⁸ cm s⁻¹ at the companion position, while the brown colored lines illustrate a symmetric unswept high-speed shock component. The left panels highlight the case of zero wind acceleration, while the right panels accelerate the shock at a constant rate a_wind = 10^5.5 cm s⁻² (outward, parallel to the line joining the two stars). The constant acceleration, contrasted to zero acceleration, decreases the total eclipse fraction from 11.33% to 8.55%, eclipse asymmetry from Δf_E = 4.75% to 1.9% and egress-ingress ratio from 2.45 to 1.58. The purple points denote the geometric center of the projected ellipses from Eq. (A8).