Spectroscopic observations of eight supernovae at intermediate redshift

Aims. We present spectra of six type Ia and two type II supernovae obtained in June 2002 at the William Herschel Telescope during a search for type Ia supernovae (SN Ia) at intermediate redshift. Methods. Supernova type identification and phase determination are performed using a fitting technique based on chi(2) minimization against a series of model templates. Results. The spectra range from z = 0.033 to z = 0.328, including one spectroscopically underluminous SN Ia at z = 0.033. This set of spectra significantly increases the sample of well-observed type SN Ia supernovae available in the range 0.15 <= z <= 0.35. Together with the twelve supernovae observed by our team in 1999 in the same redshift range, they form an homogeneous sample of seventeen type Ia supernovae with comparable signal- to- noise ratio and regular phase sampling in a still largely unexplored region of the redshift space.