Modern Rate-of-Decline Relations for Novae

A large sample of $t_2$ and $t_3$ times from the recent compilation of nova properties given in Schaefer (2025) have been analyzed to determine relationships between these two parameters. Fits were performed in both directions (from $\log t_2$ to $\log t_3$ and vice-versa) to account for the asymmetry inherent in ordinary least-squares regression, which minimizes residuals only in the dependent variable. The following best-fit relations were found: $\log t_3=(0.877\pm 0.019)\log t_2+(0.444\pm 0.027)$, and $\log t_2=(1.018\pm 0.023)\log t_3-(0.316\pm 0.037)$, corresponding to $t_3=(2.78\pm 0.17)t_2^{(0.877\pm 0.019)}$ and $t_2=(0.483\pm 0.041)t_3^{(1.018\pm 0.023)}$, respectively. Within the uncertainties, the latter relation reduces to a simple proportionality: $t_2\simeq 0.5t_3$.