Estimating Hawking radiation for exotic black holes

We study an approximation method of Hawking radiation. We analyze a massless scalar field in exotic black hole background models which have peculiar properties in black hole thermodynamics [a monopole black hole in the SO(3) Einstein-Yang-Mills-Higgs system and a dilatonic black hole in the Einstein-Maxwell-dilaton system]. A scalar field is assumed not to be coupled to matter fields consisting of a black hole background. Except for extreme black holes, we can approximate Hawking radiation well by a ``blackbody'' one with the Hawking temperature estimated at a radius of a critical impact parameter.