Spectroscopy of the type Ia supernova SN 2002er: days -11 to +215

We present an extensive set of optical spectroscopy of the nearby type Ia supernova, SN 2002er, with 24 epochs spanning -11 to +34 days. Its spectral evolution is fairly typical of a type Ia supernova although it suffers high extinction. Nevertheless, there are differences in the spectral evolution when compared to coeval spectra of other normal type Ia supernova with comparable decline-rate parameters. Modelling of the photospheric phase spectra using a homogeneous abundance distribution in the atmosphere provides a fair match to the observations, but only by pushing the adopted distance and risetime close to the observational limits. Future improvements here will require models with a more realtistic stratified abundance distribution. From simple modelling of a nebular spectrum obtained at +215d, we infer a 56Ni mass of 0.69Msun, consistent with that derived from the light curve.