  An equation of state for 2-flavor quark matter (QM) with diquark condensation
under the conditions for compact stars -$\beta$-equilibrium, charge and color
neutrality- is presented. Trapped antineutrinos prevent the formation of the
diquark condensate at moderate densities above a critical value of the
antineutrino chemical potential $\mu_{\bar \nu_e}^c$. The following
consequences are presented: 1) The star develops a 2-phase structure
($\mu_{\bar \nu_e}\geq \mu_{\bar \nu_e}^c$): a color superconducting QM core
and a normal QM shell. 2)During the cooling, when the temperature is small
enough ($T<1$ MeV) the antineutrino mean free path becomes larger than the
thickness of the normal QM shell and the antineutrinos get untrapped in a
sudden burst. The energy release is estimated as $\simeq 10^{52}$ erg and an
antineutrino pulse is expected to be observed.
