Galactic Positron Production from Supernovae

Abstract

The energy deposition into the ejecta of type Ia supernovae is dominated at late times by the slowing of positrons produced in the $β^{+}$ decays of $^{56}$Co. Fits of model-generated light curves to observations of type Ia supernovae suggest that a significant number of positrons escape the ejecta and annihilate as a delayed emission. In this work, the isotopic yields of the $β^{+}$ decay unstable nuclei, $^{56}$Co, $^{44}$Ti & $^{26}$Al are combined with the delayed annihilation fractions of each isotope for types Ia, Ib, II supernovae to generate an estimate of the positron production rate due to supernovae. It is shown that SN produced positrons can explain a sizeable fraction of the galactic positron annihilation radiation, as measured at 511 keV by the CGRO/OSSE, SMM and TGRS instruments.