Can Charge Exchange Explain Anomalous Soft X-Ray Emission in the Cygnus Loop?

Recent X-ray studies have shown that supernova shock models are unable to satisfactorily explain X-ray emission in the rim of the Cygnus Loop. In an attempt to account for this "anomalously" enhanced X-ray flux, we fit the region with a model including theoretical charge exchange (CX) data along with shock and background X-ray models. The model includes the CX collisions of O 8 + , O 7 + , N 7 + , N 6 + , C 6 + , and C 5 + with H with an energy of 1 keV u −1 (438 km s −1 ). The observations reveal a strong emission feature near 0.7 keV that cannot fully be accounted for by a shock model, nor the current CX data. Inclusion of CX, specifically O 7 + + H, does provide for a statistically significant improvement over a pure shock model.