Here we refer to the peak-to-peak amplitude of a Fourier series fit and the average of its maximum and minimum as the amplitude and the mean (or zero), respectively. Then, amplitude-normalized templates of the $H$-band and velocity curves were constructed combining the data of the 11 Cepheids (Figure \[fig:fit\_combined\]). Within the period range, the template Cepheids show similar variations in both $H$-band light and velocity. In addition, the amplitudes of the template $H$-band light curves are well correlated with those of the velocity curves, as shown in Figure \[fig:comp\_amp\]. The amplitude ratio, $A_{\rm RV}/A_{H}=135~{{\mathrm{km~s}^{-1}}}~{\rm mag}^{-1}$, is taken as the mean value for the 11 template stars, and the standard deviation is $19~{{\mathrm{km~s}^{-1}}}~{\rm mag}^{-1}$. We can use this ratio to predict velocity amplitudes based on $H$-band light curves.

[crrrrrrr]{} YZ Aur & 18.193 & 0.38 & 54\
VY Car & 18.905 & 0.40 & 66\
RU Sct & 19.703 & 0.42 & 58\
VX Cyg & 20.133 & 0.41 & 58\
RY Sco & 20.320 & 0.29 & 41\
RZ Vel & 20.397 & 0.46 & 73\
WZ Sgr & 21.851 & 0.47 & 63\
BM Per & 22.952 & 0.60 & 59\
WZ Car & 23.013 & 0.55 & 62\
