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. 
Rubina Kotak (1), Peter Meikle (1), Giuliano Pignata (2), Matthias   Stehle (3), Steve Smartt (4), Stefano Benetti (5), Wolf...