Schematic view of the wake of a pulsar companion. The pulsar is far to the left outside of the figure. The directions of the wind velocity v_w, the wind magnetic field B_w, and the convection electric field E_w are plotted on the left-hand side. The shadow is shown in gray. The Alfvén wing is shown in blue. The region from which we expect radio emissions (in yellow) is inside the wing and outside the shadow. Its largest transverse radius is R_S and its distance to the companion is l. Seen from the NS at a distance r, it subtends a solid angle Ω_σ. Any point source S in the source region can generate radio waves. Because of the relativistic aberration, their directions are contained in a narrow beam (in green) of solid angle πγ⁻². If the emission is not isotropic in the source reference frame, it is emitted in a subset of this cone (dark green tortuous line). Photons that emerge from this cone are marked with red arrows. Seen from the source point S, this dark green area subtends a solid angle Ω_beam.