Approximating the X-ray spectrum emitted from astrophysical charge exchange

摘要

Charge exchange (CX), both onto ions in the solar wind and potentially in other astrophysical contexts, can create X-ray emission lines largely indistinguishable from those created in collisional or photoionized plasmas. The prime distinguishing characteristic is in the distinctly different line ratios generated by the CX process. A complete astrophysical model of the process would require a vast number of atomic calculations; we describe here an approximate approach that will allow astronomers to evaluate the likely contribution of CX to an observed spectrum. The method relies upon an approximate calculation of the CX cross section paired with detailed atomic structure calculations used to determine the emission lines. Simulated spectra based on observed solar wind CX data are shown for both current (Suzaku) and near-term (Astro-H) missions (? 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)