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Observations and data reduction

The spectroscopic data were obtained with the 6m telescope of the Special Astrophysical Observatory of Russian Academy of Science (SAO RAS) during run in October 1999. The Long-Slit spectrograph (Afanasiev et al. [1995]) at the telescope prime focus was equipped with a Photometrics CCD-detector PM1024. The long-slit (180) spectra were obtained with the gratings of 325, 650 and 1302 grooves/mm with corresponding dispersions of 4.6, 2.4 and 1.2 Å/pixel. The widths of the slit of 1.2 and 2 were used. The scale along the slit was 0.39 /pixel. For the UM 133 the slit, centred on the brightest knot (see in Fig. 1a), was oriented along the main body with PA=22$^\circ$.

Reference spectra of an Ar-Ne-He lamp were recorded before or after each observation to provide wavelength calibration. Spectrophotometric standard stars from Massey et al. ([1988]) were observed for flux calibration. Observations have been conducted mainly under the software package NICE in MIDAS, described by Kniazev & Shergin ([1995]). Two CCD images of UM 133 in Johnson B band with an exposure time of 600 s each were obtained in photometric conditions with the 1m telescope of SAO RAS on 1999, December 6. Photometric standards from SA 92 were used for calibration.

All primary data reduction was carried out in the standard way, similar to that described in Kniazev et al. ([2000b]). Redshift and line fluxes were also measured in the standard way, as in Kniazev et al. ([2000b]).

For the simultaneous derivation of C(H$\beta$) and EW(abs) and correction for extinction we used procedure described in detail in Izotov, Thuan & Lipovetsky ([1997], hereafter ITL97). The abundances of the ionized species and the total abundances of O, Ne, N and S also have been obtained following ITL97.

The observed emission line intensities $F(\lambda)$, and those corrected for interstellar extinction and underlying stellar absorption $I(\lambda)$are presented in Table 1. The H$\beta$ equivalent width EW(H$\beta$), absorption Balmer hydrogen lines equivalent widths EW(abs), H$\beta$ flux and the extinction coefficient C(H$\beta$) are also shown in Table 1. We give here only the minimal set of lines used for chemical abundance calculations.

The surface brightness profile (SBP) for UM 133 was derived employing the method described in Kniazev et al. ([2000b]). Constructing SBP for underlying galaxy we first extracted the bright H  II region at the SW edge of the UM 133.