  Mergers of neutron stars (NS) and white dwarfs (WD) may give rise to
observable explosive transient events. We use 3D hydrodynamical (SPH)
simulations, as well as 2D hydrodynamical-thermonuclear simulations (using the
FLASH AMR code) to model the disruption of CO-WDs by NSs, which produce faint
transient events. We post-process the simulations using a large nuclear network
and make use of the SuperNu radiation-transfer code to predict the
observational signatures and detailed properties of these transients. We
calculate the light-curves (LC) and spectra for five models of NS - CO-WD
mergers. The small yields of Ni56 (few x 0.001Msun) results in faint,
rapidly-evolving reddened transients (RRTs) with B (R) - peak magnitudes of ~
-12 (-13) to ~ -13 (-15), much shorter and fainter than both regular and
faint/peculiar type-Ia SNe. We show that the spectra of RRTs share some
similarities with rapidly - evolving transients such as SN2010x, though RRTs
are significantly fainter, especially in the I/R bands, and show far stronger
Si lines. We estimate that the upcoming Large Synoptic Survey Telescope could
detect RRTs at a rate of ~ 10 - 70 yr^-1, through observations in the R/I
bands.
