Upper limits of the $^{22}$Na yield from O-Ne nova

Abstract

The radioactive isotope $^{22}$Na is one of the primary tracer isotopes that may potentially be detectable by gamma-ray spectroscopy. This isotope is predicted to be produced in ONe nova explosions, yet no detection of its 1.275 MeV gamma-ray signature has been reported so far. In particular, 6 years of COMPTEL observations of the galactic bulge, a region that should be particularily rich in nova explosions, have only led to an upper-limit. In this paper we will present the implications of the COMPTEL upper flux limit on the permissible $^{22}$Na yield for ONe novae. We base our analysis on extensive Monte-Carlo simulations of galactic 1.275 MeV emission that were constrained by the most recent results of galactic nova rates and distributions. We demonstrate that the non-detection of the 1.275 MeV line from the galactic bulge implies a solid upper $^{22}$Na yield limit in agreement with current theoretical nucleosynthesis calculations.