FWHM of the broad line in the absence of CRs and for different levels of electron-ion equilibrium. The two data points represent the FWHM as measured by Helder et al. (2010) in the NE and SW regions of SNR 0509-67.5. Because the shock velocity is rather uncertain, the horizontal coordinate of the two points can actually be appreciably different from that in the figure, which is taken directly from the work of Helder et al. (2010).