Erlangen 2026 – scientific programme

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EP: Fachverband Extraterrestrische Physik

EP 1: Astrophysics I

EP 1.2: Talk

Monday, March 16, 2026, 15:15–15:30, KH 01.019

Contribution of Stellar flares to the 511keV galactic positron budget — •Saurabh Mittal and Thomas Siegert — Julius-Maximilian-Universität, Würzburg

The origin of the Galactic 511 keV positron annihilation line has been a mystery for five decades. One proposed explanation is positron production in stellar flares, motivated by the detection of the 511 keV line in solar flares and by the association of this emission with old stellar populations. In this work, we explore this scenario using two complementary approaches. First, we build a theoretical model to estimate the quasi-persistent 511 keV emission from flaring stars. Starting from solar flare observations, we construct empirical scaling relations between flare energy and 511 keV luminosity and extend them to Galactic stellar populations using flare-frequency-energy distributions for different spectral types. In parallel, we analyze INTEGRAL/SPI data in the 511 keV band using combinations of known point sources and simple spatial templates, such as disk and bulge components modeled as two-dimensional Gaussians. We also test alternative descriptions in which no bulge template is assumed and the emission is instead described by a disk component together with a population of globular clusters, scaled by their masses and distances. This ongoing work aims to assess whether stellar flares can plausibly account for the observed Galactic 511 keV emission.

Keywords: Positrons; Gamma rays: general; Stars: flares; Galaxy: globular clusters: general