ESC observations of SN 2005cf - II. Optical spectroscopy and the high-velocity features

The ESC-RTN optical spectroscopy data set for SN 2005cf is presented and analyzed. The observations range from -11.6 and + 77.3 days with respect to B-band maximum light. The evolution of the spectral energy distribution of SN 2005cf is characterized by the presence of high velocity Si II and Ca II features. SYNOW synthetic spectra are used to investigate the ejecta geometry of silicon. Based on the synthetic spectra, the Si II high-velocity feature appears detached at 19 500 km s(-1). We also securely establish the presence of such a feature in SN 1990N, SN 1994D, SN 2002er, and SN 2003du. In a morphological study both the Ca II IR triplet and H&K absorption lines of SN 2005cf show high-velocity features centered around 24 000 km s(-1). When compared with other type Ia SNe based on the scheme presented in Benetti et al. ( 2005, ApJ, 623, 1011), SN 2005cf definitely belongs to the LVG group.