Charge exchange, from the sky to the laboratory: A method to determine state-selective cross-sections for improved modeling

Abstract

Charge exchange (CX) is a semi-resonant recombination process that can lead to spectral line emission in the X-ray band. It occurs in nearly any environment where hot plasma and cold gas interact: in the solar system, in comets and planetary atmospheres, and likely astrophysically, in, for example, supernova remnants and galaxy clusters. It also contributes to the soft X-ray background. Accurate spectral modeling of CX is thus critical to properly interpreting our astrophysical observations, but the commonly used CX models in popular spectral fitting packages often rely on scaling equations and may not accurately describe observations or laboratory measurements. This paper introduces a method that can be applied to high-resolution CX spectra to directly extract state-selective CX cross-sections for electron capture, a key parameter for properly simulating the resulting CX spectrum.