Gamma-ray line signals from supernovae within 100 Mpc

The average number of supernovae per year detectable by gamma-rays emitted during the decay of Ni-56 to Fe-56 is estimated for galaxies within 100 Mpc as a function of limiting sensitivity using standard supernova yields and the Sternberg and Asiago supernova catalogs. An instrument having a broad-line (5000 km s(-1)) sensitivity of 2 x 10(-6) gamma s(-1) cm(-2) should detect a minimum of 1.0 +/- 0.5 Type Ia supernovae per year, and observe all Type Ia events from the Virgo, Fornax, and possibly the Hydra galaxy clusters. Roughly 10%-30% of all Type Ia supernovae within 100 Mpc are detectable at this flux sensitivity. Instruments having broad-line flux sensitivities larger than 1.5 x 10(-5) gamma s(-1) cm(-2) will probably only detect rare Type Ia supernovae within 10 Mpc, such as SN 1972E or SN 1991T. Flux sensitivities of similar or equal to 2 x 10(-6) gamma s(-1) cm(-2) to intermediate-width gamma-ray lines should enable the detection of a minimum of 0.2 +/- 0.2 Type Ib and Type Ic supernovae per year, and easily allow events similar to SN 1983N and SN 1985F to be seen. Instruments of the near future will not detect the narrow-line gamma rays from any Type II supernovae that originate beyond the Local Group of galaxies. These number and rate estimates provide guidelines for the design of future gamma-ray missions.