Observations

Spectroscopic observations of KUG 1031+398 were carried out with the spectrograph CARELEC (Lemaître et al. 1989) attached to the Cassegrain focus of the Observatoire de Haute Provence (OHP) 1.93 m telescope. The detector was a 512$\times$512 pixels, 27$\times$27 $\mu$m Tektronix CCD. We used a 600 lmm^-1 grating giving a dispersion of 66 Åmm^-1. On January 10, 1997 we obtained a 20 min exposure in the range $\lambda\lambda$6175-7075 Å, on March 4, a 20 min exposure in the range $\lambda\lambda$4780-5780 Å, and three more on March 5.

The slit width was 21, corresponding to a projected slit width on the detector of 52 $\mu$m, or 1.9 pixel. The resolution, as measured on the night sky emission lines, was 3.4 Å FWHM in the blue and 3.5 Å in the red. In both cases the galaxy nucleus was centered on the slit and 3 columns of the CCD ($\sim$ 32) were extracted, corresponding to $\sim$ 4 kpc at the distance of the galaxy (with $H\rm _{o}$ = 50 kms^-1Mpc^-1).

The spectra were flux calibrated using the standard stars EG 247 (Oke 1974) and Feige 66 (Massey et al. 1988), observed with the same instrumental settings; these standards were also used to correct the red spectrum for the atmospheric B band at $\lambda$6867 Å (Fig. b).

 

Figure:   Blue (a) and red (b) spectra of KUG 1031+398 in the rest frame; in (b) we also give the spectrum before correcting for the atmospheric absorption (dotted line). The narrow line-core components (c and d) were fitted with Gaussians and subtracted from the original data, the result being shown in (e) to (h). In (e) and (f), we show our best fit (solid line) together with the data points (crosses); the lower solid lines represent the residuals.