Bessell $R$-band magnitudes obtained as part of the Lick Observatory Supernova Search [LOSS; @Filippenko01] photometry follow-up program. We then synthesized Bessell $R$-band magnitudes from our late-time spectra (taken on 2002 Oct. 8 and 2002 Nov. 8) and compared them to the magnitudes derived from the photometry, assuming a linear decline in magnitude during the last three months of 2002. In order for our spectra to match the photometry, and thus for the absolute flux to be accurate, our spectra from 2002 Oct. 8 and 2002 Nov. 8 must be scaled up by factors of 4.41 and 1.29, respectively. Due to the photometric measurements alone, the uncertainty in the absolute flux of each of these two spectra is [$\sim\!\!$ ]{}25%.

We modeled both late-time spectra of [SN 2001ig]{} using a code that computes nebular-line emission from a gaseous cloud. The gas is heated by the deposition of $\gamma$-rays and positrons produced by the decay of radioactive $^{56}$Ni (which is produced in the SN explosion itself) into $^{56}$Co and then into stable $^{56}$Fe. The energy thus deposited in the gas is thermalized collisionally, which leads to excitation and ionization of the gas. Heating is balanced by cooling, which takes place via line 