Kinematics of a moving shell. Compare with Fig. 3 in MK98 for a stationary shell. Left: scheme of the kinematics of a shell with radius r_s and phase velocity v_s. The shell is composed of stars on radial orbits with radial velocity v_r and LOS velocity v_los. Right: the LOSVD at projected radius R = 0.9r_s, where r_s = 120 kpc (parameters of the shell are highlighted in bold in Table 1), in the framework of the model of radial oscillations (Sect. 2.3). The profile does not include stars of the host galaxy, which are not part of the shell system, and is normalized, so that the total flux equals one. a) The LOSVD showing separate contributions from inward and outward stars; b) the same profile, separated for contributions from the half of the host galaxy closer to the observer (the one including point B) and the more distant half (includes point A).