SIMBAD references

New improved empirical calibrations for the determination of electron temperatures and oxygen and nitrogen abundances in H II regions from the strong emission lines of oxygen, nitrogen, and sulfur are given. They are derived using spectra of H II regions with measured electron temperatures as calibrating data. Calibration relations are given separately for three classes of H II regions: cool, warm, and hot ones. Criteria for assigning a H II region to one of these classes are suggested. We find that classification ambiguities arise only in the case of hot H II regions with enhanced nitrogen abundances. The derived calibrations provide reliable abundances for H II regions: the mean difference between oxygen abundances determined from the calibrations and T_e-based oxygen abundances is ∼0.075 dex, while it is ∼0.05 dex for nitrogen abundances.