SIMBAD references

The determination of temperature (T_eff) of the ionizing stars of HII regions was considered. In this work we used photoionization models for HII regions ionized by a single star to show that the index R=log([OII]λλ3726+3729/[OIII]λ5007) can be used to estimate T_eff. The relation R vs. T_eff proved to be rather independent of the chemical abundances, but strongly dependent on the ionization parameter of the nebula. In order to check the reliability of using R for temperature determination, we compared the values of T_eff obtained via the index R for a sample of HII regions with data available in the literature with independent estimations.