Searching for 511 keV annihilation line emission from galactic compact objects with IBIS

TL;DR

This study used the IBIS imager on INTEGRAL to search for 511 keV gamma-ray emission from galactic compact objects over five years but found no significant point sources, supporting the idea of positron propagation in the galaxy.

Contribution

First comprehensive 5-year all-sky search for 511 keV sources with IBIS, providing constraints on galactic positron sources and propagation.

Findings

No significant 511 keV point sources detected.

Supports positron propagation hypothesis in the interstellar medium.

Provides sensitivity estimates for future searches.

Abstract

The IBIS imager on board the INTEGRAL satellite, thanks to the large field of view and good sensitivity, gave us a unique opportunity to search for possible 511 keV point sources either previously unknown or associated to known objects such as X-ray binaries or supernovae. The IBIS sensitivity at 511 keV depends on the gamma ray detector quantum efficiency at this energy and on the background. Both these quantities have been estimated. Reducing all the available IBIS data up to April 2008 we have produced a 5 years full sky 511 keV map with 10 Ms exposure in the Galactic Center. We did not find any significant signal at this energy. The lack of detection of 511 keV galactic point sources is in agreement with the idea that a significant part of the galactic positrons originates in compact objects and then propagates in the interstellar medium.