Galactic Positrons from Thermonuclear Supernovae

Type Ia supernovae (SNe Ia) may originate from a wide variety of explosion scenarios and progenitor channels. They exhibit a factor of approximate to 10 difference in brightness and thus a differentiation in the mass of Ni-56 -> Co-56 -> Fe-56. We present a study on the fate of positrons within SNe Ia in order to evaluate their escape fractions and energy spectra. Our detailed Monte Carlo transport simulations for positrons and gamma-rays include both beta (+) decay of Co-56 and pair production. We simulate a wide variety of explosion scenarios, including the explosion of white dwarfs (WDs) close to the Chandrasekhar mass (M (Ch)), He-triggered explosions of sub-M (Ch) WDs, and dynamical mergers of two WDs. For each model, we study the influence of the size and morphology of the progenitor magnetic field between 1 and 10(13) G. Population synthesis based on the observed brightness distribution of SNe Ia was used to estimate the overall contributions to Galactic positrons due to escape from SNe Ia. We find that this is dominated by SNe Ia of normal brightness, where variations in the distribution of emitted positrons are small. We estimate a total SNe Ia contribution to Galactic positrons of <2% and, depending on the magnetic field morphology, M (Ch) and sub-M (Ch), respectively.

Automated summary

This study investigates the fate of positrons within Type Ia supernovae (SNe Ia) and evaluates their escape fractions and energy spectra. Monte Carlo transport simulations are used to study the influence of different explosion scenarios and progenitor magnetic fields. Population synthesis based on observed brightness distribution is used to estimate the overall contributions of SNe Ia to Galactic positrons.