Supernovae as the site of the r-process: Implications for gamma-ray astronomy

We discuss how detection of gamma-ray emission from the decay of r-process nuclei can improve our understanding of r-process nucleosynthesis. We find that a gamma-ray detector with a sensitivity of ∼ 10^-7γ cm^-2 s^-1 at Eγ ≈ 100-700 keV may detect the emission from the decay of ¹²⁵Sb, ¹³⁷Cs, ¹⁴⁴Ce, ¹⁵⁵Eu, and ¹⁹⁴Os produced in a future Galactic supernova. In addition, such a detector may determine the emission from the decay of ¹²⁶Sn in the Vela supernova remnant and the diffuse emission from the decay of ¹²⁶Sn produced by past supernovae in our Galaxy. The required detector sensitivity is similar to what is projected for the proposed Advanced Telescope for High Energy Nuclear Astrophysics (ATHENA). Both the detection of gamma-ray emission from the decay of several r-process nuclei (e.g., ¹²⁵Sb and ¹⁹⁴Os) produced in future Galactic supernovae and the detection of emission from the decay of ¹²⁶Sn in the Vela supernova remnant would prove that supernovae are a site of the r-process. Furthermore, the former detection would allow us to determine whether or not the r-process nuclei are produced in relative proportions specified by the solar r-process abundance pattern in supernova r-process events. Finally, detection of diffuse emission from the decay of ¹²⁶Sn in our Galaxy would eliminate neutron star-neutron star mergers as the main source for the r-process nuclei near mass number A ∼ 126.