Probing r-Process Production of Nuclei Beyond ^(209)Bi with Gamma Rays

Abstract

We estimate gamma-ray fluxes due to the decay of nuclei beyond ^(209)Bi from a supernova or a supernova remnant assuming that the r-process occurs in supernovae. We find that a detector with a sensitivity of ~10^(-7) γ cm^(-2) s^(-1) at energies from ~40 keV to ~3 MeV may detect fluxes due to the decay of ^(226)Ra, ^(229)Th, ^(241)Am, ^(243)Am, ^(249)Cf, and ^(251)Cf in the newly discovered supernova remnant near Vela. In addition, such a detector may detect fluxes due to the decay of ^(227)Ac and ^(228)Ra produced in a future supernova at a distance of ~1 kpc. Because nuclei with mass numbers A > 209 are produced solely by the r-process, such detections are the best proof for a supernova r-process site. Further, they provide the most direct information on yields of progenitor nuclei with A > 209 at r-process freeze-out. Finally, detection of fluxes due to the decay of r-process nuclei over a range of masses from a supernova or a supernova remnant provides the opportunity to compare yields in a single supernova event with the solar r-process abundance pattern.