Spectroscopy of the type Ia supernova SN 2002er: Days –11 to +215

¹ Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London, SW7 2AZ, UK
² European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
³ Max-Planck-Institut für Astrophysik, PO Box 1317, 85741 Garching, Germany
⁴ Department of Physics and Astronomy, Queen's University Belfast, Belfast, BT7 1NN, Northern Ireland, UK
⁵ Osservatorio Astronomico di Padova, vicolo dell'Osservatorio 5, 35122 Padova, Italy
⁶ Isaac Newton Group of Telescopes, Apartado de Correos 321, 38700 Santa Cruz de la Palma, Canary Islands, Spain
⁷ Osservatorio Astronomico di Trieste, Via Tiepolo, 11, 34131 Trieste, Italy

Received: 25 January 2005
Accepted: 14 March 2005

Abstract

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 realistic stratified abundance distribution. From simple modelling of a nebular spectrum obtained at +215 d, we infer a ⁵⁶Ni mass of 0.69 , consistent with that derived from the light curve.