SNR model parameters for the Monogem Ring SNR. We assumed a radius of 58 pc at D = 300 pc. The estimated uncertainty on the radius is 10%. The color scale indicates the calculated age of the respective model. The vertical dashed and dotted lines show the ambient ISM density n₀ lower and upper limits, respectively, for different filling factors. The density n₀ was inferred from the spectral analysis for D = 300 pc. The black dashed and dotted lines show n₀ for f = 1, while the red lines show n₀ for f = 0.5. Models with predicted radii and X-ray temperatures outside the derived confidence intervals are not shown. The SNR evolutionary models are Sedov-Taylor (a) and Cloudy ISM (b) for τ = 2 (Leahy et al. 2017). The color scale for the age is in absolute values for better comparability with the other SNRs. The black solid contours on top of the surface plot denote different levels of the age in steps of 10 000 yr, similar to the color scale shown on the right.