Annihilation of positrons from ${}^{22}$Na in novae

Abstract

We explore for the first time effects of the magnetic field on the escape of ${}^{22}$Na positrons and on the flux evolution of annihilation 511 keV line in novae. It is shown that for the white dwarf magnetic field of $\sim 10^6$ G the field of the expanding nova shell is able to significantly impede positrons escape and increase the time of the nova emission in 511keV up to hundreds days.

Accepted by Astronomy Letters