Particle Production in Sgr A* and in the Active Galactic Nuclei (AGN) (with S. Markoff and F. Melia) Astrophysical Journal (Letters) 489, 47 (1997) and Astrophysical Journal 522, 870 (1999).

We study particle production mechanism in galactic and extragalactic astrophysical sources with special emphasis on energy losses processes for high energy protons and energy dependence of the hadronic cross section and pion multiplicities. We expect that the photon energy spectrum that we will obtain as the end product of the cascade will have distinctive shape and its comparison with recent observation will either confirm or exclude the possibility that cascade is initiated by very high energy protons. We find that a careful treatment of the high-energy p-p scattering suggest that Sgr A* is very likely a black hole of 10^6 solar masses.