  We carry out a comprehensive study of supernova ejecta-companion interaction
in massive binary systems. We aim to physically understand the kinematics of
the interaction and predict observational signatures. To do this we perform
simulations over a vast parameter space of binary configurations, varying the
masses of the progenitor and companion, structure of the companion, explosion
energy, and orbital separation. Our results were not so consistent with
classical models by Wheeler et al. 1975, sometimes deviating by an order of
magnitude. We construct an alternative simple model which explains the
simulated results reasonably well and can be used to estimate impact velocities
for arbitrary explosion profiles and companion star structures. We then
investigate the long term evolution after the supernova, where the companion
can be inflated by the energy injected into the star. We find that the
companion can become more than an order of magnitude overluminous straight
after the supernova, but quickly fades away after $\sim10$ years and returns to
its original luminosity in about a thermal timescale of the star. Finally, we
also discuss the possible surface contamination of heavy elements from the
slower ejecta.
