  Super-Chandrasekhar remnants of double white dwarf mergers could sometimes
collapse into a rapidly rotating neutron star (NS), accompanying with a mass
ejection of a few times $0.01M_{\odot}$. Bright optical transient emission can
be produced by the ejecta due to heating by radioactivities and particularly by
energy injection from the NS. Since the merger remnants before collapse
resemble a star evolving from the asymptotic giant branch phase to the
planetary nebula phase, an intense dusty wind is considered to be driven about
several thousand years ago before the collapse and surround the remnant at
large radii. Therefore, the optical transient emission can be somewhat absorbed
and scattered by the dusty wind, which can suppress the peak emission and cause
a scattering plateau in optical light curves. Several years later, as the
ejecta finally catches up with the wind material, the shock interaction between
them can further give rise to a detectable radio transient emission on a
timescale of tens of days. Discovery of and observations to such dust-affected
optical transients and shock-driven radio transients can help to explore the
nature of super-Chandrasekhar merger remnants and as well as the density and
type ratios of double white dwarf systems, which is beneficial in assessing
their gravitational wave contributions.
