Constraints on the Abundance of PBHs from X-ray Quasar Microlensing Observations: Substellar to Planetary Mass Range

A. Esteban-Gutiérrez, E. Mediavilla, J. Jiménez-Vicente +1

We use X-ray observations of quasar microlensing (sensitive to smaller compact objects than in the optical) to study the possible presence of a population of low mass black holes (…