  A rapidly rotating and highly magnetized remnant neutron star (NS; magnetar)
could survive from a merger of double NSs and drive a powerful relativistic
wind. The early interaction of this wind with the previous merger ejecta can
lead to shock breakout (SBO) emission mainly in ultraviolet and soft X-ray
bands, which provides an observational signature for the existence of the
remnant magnetar. Here we investigate the effect of an anisotropic structure of
the merger ejecta on the SBO emission. It is found that bolometric light curve
of the SBO emission can be broadened, since the SBO can occur at different
times for different directions. In more detail, the profile of the SBO light
curve can be highly dependent on the ejecta structure and, thus, we can in
principle use the SBO light curves to probe the structure of the merger ejecta
in future.
