X-ray and gamma-ray limits on the primordial black hole abundance from Hawking radiation

Abstract

The non-observation of extragalactic Hawking radiation from primordial black holes of 1016 g sets a conservative strong bound on their cosmological abundance. We revisit this bound and show how it can be improved (both in mass reach and strength) by an adequate modeling of the combined AGN and blazar emission in the MeV range. We also estimate the sensitivity to the primordial black hole abundance of a future X-ray experiment capable of identifying a significantly larger number of astrophysical sources contributing to the diffuse background in this energy range.