The Klein-Gordon oscillator and the proper time formalism in a Rigged Hilbert sapace

The implications of manifestly covariant formulation of relativistic quantum mechanics depending on a scalar evolution parameter, canonically conjugated to the variable mass, is still an unsettled issue. In this work we find a complete set of generalized eigenfunctions of the Klein-Gordon Oscillator in the above mentioned formulation, in the Rigged Hilbert Space with Tempered Ultradistributions. We briefly comment on some models where this solution could be applied.