2 Observations and reductions

The spectroscopic observations were performed using a Boller & Chivens spectrograph at the Cassegrain focus of the ESO 1.52 m telescope in La Silla (Chile). A UV-flooded thinned Loral Lesser CCD #39 ( $2048 \times 2048$, 15 $\mu$m/pixel) was used as detector; it gives a high quantum efficiency in the blue and in the UV. The setup employed is the same used to investigate other emission-line objects at the 1.52 m telescope (Pereira et al. 2001). Two instrumental setups were employed. The first made use of grating #23 with 600 l/mm, providing a resolution of 4.6 Å  in the range 3500 Å-7500 Å. The other setup adopted grating #31 with 1200 l/mm, resulting in a resolution of 1.9 Å  in the range 3100-5100 Å.

The spectra were reduced using standard IRAF tasks, from bias subtraction, flat-field correction, through spectral extraction and wavelength and flux calibration. Spectrophotometric standards from Oke (1974) and Hamuy et al. (1994) were also observed. The slit orientation in the range (3110 Å-5100 Å) was aligned with the parallactic angle in order to minimize the light loss due to atmospheric refraction. Table 1 shows the log of observations. Column 1 lists the objects by their number in the SS73 survey. Column 2 gives the date of our observations, Col. 3 shows the wavelength coverage and the exposure time is given in the last column.