Determination of temperature of the ionizing stars of H II regions

The determination of temperature (Teff) of the ionizing stars of regions was considered. In this work we used photoionization models for regions ionized by a single star to show that the index R=log ([ O II] (lambda) (lambda) 3726+3729/[ O III] (lambda)5007) can be used to estimate Teff. The relation R vs. Teff 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 Teff obtained via the index R for a sample of regions with data available in the literature with independent estimations.