Can flaring stars explain the annihilation line from the Galaxy bulge?

TL;DR

This paper explores whether flaring low-mass stars could be the primary source of the electron-positron annihilation line observed from the Galactic bulge, offering a potential alternative to other astrophysical sources.

Contribution

It proposes and evaluates the hypothesis that cumulative positron production from flaring low-mass stars can account for the observed annihilation line in the Galactic bulge.

Findings

Flaring stars can produce significant positrons.

Positron production from stars may explain the annihilation line.

Stars could be the main positron source in the Galactic bulge.

Abstract

Electron-positron annihilation line from a Galactic center direction was discovered by the balloon-borne germanium gamma-ray telescope, and confirmed by OSSE experiment of CGRO mission. Extensive observations by INTEGRAL observatory permit to determine properties of the annihilation line from Galactic bulge. Possible sources of $e^{+}$ already discussed are supernovae explosions, microquasars, gamma-ray bursts, tidal disruption events, activity near black hole of Sgr A*, $e^{+}$ generation by subrelativistic cosmic rays, or even dark matter. One remarkable feature of the line emission is an absence of resolved point like sources. Any model should take into account this feature. We consider flares of low-mass stars as a possible cumulative $e^{+}$ source of the observed annihilation line from the bulge. Our estimations show that $e^{+}$ production by numerous flaring stars in Galaxy bulge can be significant, or even the main source of $e^{+}$ responsible for the annihilation line observed from the central part of our Galaxy.