Beschreibung
X-ray binaries (XRBs) are cosmologically significant sources of heating and pre-ionisation in the early Universe, dominating the high-redshift X-ray background throughout Cosmic Dawn and the Epoch of Reionisation (EoR). Population III XRBs are a largely homogeneous population that dominate heating in minihaloes, while Population II X-ray binaries are a highly heterogeneous population, with a composition and initial mass function that chemically evolve throughout the EoR. Soft X-rays from XRBs are major contributors to
the heating of the intergalactic medium, and are therefore expected to be important drivers of the evolution of the 21-cm signal. In this talk I will present a new model of the X-ray background throughout cosmic time, derived from population-synthesis simulations of XRBs. I will discuss how observations of local XRBs can help constrain the average properties of high-redshift XRBs and their chemical evolution.