INTEGRAL/IBIS search for e−e+ annihilation radiation from the galactic center region

Electron–positron annihilation radiation from the Galactic Center Region has been detected since the seventies, but its astrophysical origin is still a topic of a scientific debate. We have analyzed data of the gamma-ray imager IBIS/ISGRI onboard of ESA’s INTEGRAL platform in the e−e+ line. During the first year of the missions Galactic Center Deep Exposure no evidence for point sources at 511 keV has been found in the ISGRI data; the 2σ upper limit for resolved single point sources is estimated to be 1.6 × 10−4 ph cm−2 s−1.