Reassess the Galactic 511 keV bound in the presence of circumstellar media

Quantitatively reassess the Galactic 511 keV constraint on feebly interacting particle positron injection by incorporating the occurrence rate and distribution of circumstellar-medium properties among Galactic core-collapse supernovae, including the fraction of positrons that slow down and annihilate locally rather than entering the interstellar medium.

Background

The paper notes that conventional Galactic 511 keV bounds from feebly interacting particles assume that most positrons produced outside the progenitor environment enter the interstellar medium and contribute to the Galactic positron population. Dense circumstellar material can instead stop and annihilate a fraction of these positrons locally, weakening the conventional bound.

Determining the magnitude of this weakening requires a population-level treatment of Galactic core-collapse supernovae that accounts for the occurrence rate and distribution of circumstellar-medium properties. The paper explicitly leaves this quantitative reassessment unresolved.