  We will present a method for building a consistent AQFT on Schwarzschild
spacetime for a thermal system ruled by an interacting and massive scalar
field, extending the methods and the results of K. Fredenhagen and F. Lindner
valid for the flat case. In particular we will discuss the asymptotic
properties of the two-point function of a thermal (KMS) state in order to
obtain finite expectation values for the observables of the theory.
