Stellar flares to explain the galactic 511 keV emission
Saurabh Mittal, Thomas Siegert
Lehrstuhl für Astronomie, Universität Würzburg
Where do the positrons in the Milky Way come from? This question has been under discussion for five decades with many different sources and mechanisms being used to explain this. One such mechanism is the observed 511 keV line and ortho-Ps continuum in solar flares. Previous studies have detected the 511 keV line only from high energy solar flares but flares of all energies might contribute to this line. Other stars flare in a similar manner as the Sun with a similar flare frequency energy distribution. Based on these preconditions, and using data from Fermi/GBM, RHESSI, INTEGRAL/SPI, a relation between the 511 keV line luminosity and the flare energy can be developed. This model developed for the solar flares will be extended to populations of stars, such as in globular clusters of the Milky Way, to explain the origin of the galactic gamma-ray emission line at 511 keV and to possibly reduce the need for many different source types to explain the current observations. In the course of this work, we intend to measure the 511 keV gamma-ray emission from the Sun with gamma-ray monitors, and correlate it with the energy of the solar flare. After establishing a correlation, we will model the production and transport of positrons in the solar atmosphere with INTEGRAL/SPI observations. Finally, simulations with the future COSI-SMEX mission will be performed to validate the correlation and the annihilation physics of positrons with better sensitivity.