Exponential decay for Maxwell equations with a boundary memory condition

We study the asymptotic behavior of the solution of the Maxwell equations witha boundary condition of memory type. We consider a `Graffi' type free energy and we prove that, if the memory kernel exponentially decays and the domain is strongly star shaped, then the energy of the solution exponentially decays. We also prove that the exponential decay of the memory kernel is a necessary condition for the exponential decay of the solution.