Posterior distributions of the parameters that describe the exo-cometary sodium lines on the night of February 17, 2004, shown in Fig. 6. Because the observed Na I lines are highly optically thin, τ₀ and f were not independently constrained. Instead, we fixed f to 1 and converted τ₀ into line depth D, which is constrained to 0.89 ± 0.13%. Note that β may be elevated due to unmodeled variance in the spectrum caused by residuals from the telluric correction process.