  We study properties of compact stars with the deconfinement phase transition
in their interiors. The equation of state of cold baryon-rich matter is
constructed by combining a relativistic mean-field model for the hadronic phase
and the MIT Bag model for the deconfined phase. In a narrow parameter range two
sequences of compact stars (twin stars), which differ by the size of the quark
core, have been found. We demonstrate the possibility of a rapid transition
between the twin stars with the energy release of about $10^{52}$ ergs. This
transition should be accompanied by the prompt neutrino burst and the delayed
gamma-ray burst.
