Notes. The favorite parameters correspond to those of model W15-IIb-sh-HD-1eta-az in Table 1. The reference density of the shell, n_sh, the shell radius and thickness, r_sh and σ, the angle θ (measured in the plane of the sky, about the y-axis, counterclockwise from the west), the angle ϕ (measured about the z-axis counterclockwise from the plane of the sky) and the scale length of the shell density, H, are used in Eq. (1) to describe the CSM. The total mass of the shell, M_sh, the masses of the SE and NW hemispheres of the shell, M_SE and M_NW, and the peak densities of the shell in the SE and NW directions, n_SE and n_NW, are derived from the simulations. ^(a)The density n_sh = 10 cm⁻³ if ϕ = 0. ^(b)The mass of the shell is M_sh = 1.3 M_⊙ if ϕ = 0.