Chandra X-ray spectra of the extended emission of ζ Ophiuchi. Left: Chandra X-ray spectra of the extended emission region (black) and the background (red). The best-fit models are shown as solid lines and the fit residuals are shown in the lower panel. Right: extended emission spectrum only with the additive model components shown. The green dash-dot-dot line represents the combined NXB components constrained using the stowed observations, the dashed blue lines show the ζ Ophiuchi emission components, the magenta dash-dot line is the AXB component, and the red solid line shows the diffuse emission component.