  We perform the first nonlinear and self-consistent study of the merger and
ringdown of a black hole mimicking object with stable light rings. To that end,
we numerically solve the full Einstein-Klein-Gordon equations governing the
head-on collisions of a series of binary boson stars in the large-mass-ratio
regime resulting in spinning horizonless remnants with stable light rings. We
broadly confirm the appearance of features in the extracted gravitational
waveforms expected based on perturbative methods: the signal from the prompt
response of the remnants approaches that of a Kerr black hole in the
large-compactness limit, and the subsequent emissions contain periodically
appearing bursts akin to so-called gravitational wave echoes. However, these
bursts occur at high frequencies and are sourced by perturbations of the
remnant's internal degrees of freedom. Furthermore, the emitted waveforms also
contain a large-amplitude and long-lived component comparable in frequency to
black hole quasi-normal modes. We further characterize the emissions, obtain
basic scaling relations of relevant timescales, and compute the energy emitted
in gravitational waves.
