Photoionization Models of Iron-Rich Ejecta in SN 1885

The recent discovery by Fesen et al. [1] of the remnant of S Andromedae, the historic supernova of 1885 observed a mere 16\textacutedbl from the nuclear center of M31, brings to two the number of supernovae whose ejecta have been observed successfully in absorption: SN 1006 (Type Ia; Wu et al. [2]; Fesen et al. [3]; Hamilton and Fesen [4]) and now SN 1885 (Type I peculiar; de Vaucouleurs and Corwin [5]). In the discovery image, SN 1885 appears as an unresolved spot of Fe I absorption silhouetted against the starry blaze of M31 s bulge. From the observed absorption contrast, Fesen et al. [1] estimate that SN 1885 has an Fe I diameter of 0.3\textacutedbl, corresponding to an expansion velocity of \textpm5,000 km s—1.