are determined by oscillator strengths and the approximation of a Boltzmann distribution of the lower-level populations with a temperature of $T_{\rm exc}$.

We produced models consisting of only [Ca$\,$]{} and with only [Si$\,$]{} and [Ca$\,$]{} to isolate their affect on the profile of the Ca H&K feature. For all models, we set $T_{\rm BB} =
10000$ K, $v_{\rm ph} = 10000$ [kms$^{-1}$]{}, $v_{\rm max} = 80000$ [kms$^{-1}$]{}, and $v_{e} = 3000$ (for [Si$\,$]{}) and 2000 [kms$^{-1}$]{} (for [Ca$\,$]{}). We chose $\tau = 5$ and 4 for [Si$\,$]{} and [Ca$\,$]{}, respectively. These parameters were chosen such that when $T_{\rm
  exc} = 10000$ K, the model Ca H&K line profile was visually similar to that of the median spectrum of the sample. Keeping all other parameters fixed, we varied $T_{\rm exc}$ from 5000 to 20000 K. A subset of the models spanning this range are presented in Figure \[f:sspec\].

![image](synow_spec){width="6.8in"}

As seen in Figure \[f:sspec\], the inclusion of [Si$\,$]{} dramatically changes the Ca H&K profile shape, making it stronger, broader, and bluer. Although the [Si$\,$]{} $\lambda 3858$ feature may be stronger in the models than in real SN spectra, the [Si$\,$]{} $\lambda 6355$ and the Ca H&K features appear to have reasonable 