IOWA STATE UNIV,DEPT PHYS & ASTRON,AMES,IA 50011
; ACAD SINICA,INST PHYS,TAIPEI,TAIWAN
; ACAD SINICA,INST HIGH ENERGY PHYS,BEIJING,PEOPLES R CHINA
We determine the constraints on the anomalous top-quark coupling associated with the flavor-changing neutral current vertex <(t)over bar c gamma> from the limits on the b-quark rare decay b --> s gamma and nonstandard top-quark decays. Based on these constraints, we discuss the experimental observability of the rare decay mode t --> c gamma, both at the Fermilab Tevatron with a luminosity upgrade and at the CERN LHC.