Line intensity ratio $\frac{I_{6.9}}{I_{6.7}}$ vs. EW_6.7 plot for sources emitting a 6.7 keV line. Error bars indicate 1σ uncertainty. Mean values of $\frac{I_{6.9}}{I_{6.7}}$ and EW_6.7 for different CV-types from Xu et al. (2016) are shown for comparison. The EW_6.7 and $\frac{I_{6.9}}{I_{6.7}}$ values of the GCXE and GRXE are taken from Nobukawa et al. (2016). The dots with blue (abundance Z_ʘ) and green (abundance 2Z_ʘ) lines shows the values of EW_6.7 and $\frac{I_{6.9}}{I_{6.7}}$ expected from collisionally ionised plasma at different temperatures.