SIMBAD references

Theoretical temperature fluctuations (t²) are obtained for typical planetary nebula conditions.
Result. are given for the temperature fluctuation of the most commonly observed ions (H⁺, N⁺, O⁺, O⁺⁺, Ne⁺⁺, S⁺, and S⁺⁺). Since the results show that t² is more important for planetary nebulae (PNe) with high stellar temperatures, we discuss some observed PNe with stellar temperature greater than 100000K. For these objects, the ionic abundances relative to H⁺ are calculated with and without considering the temperature fluctuation. The calculations show that the ionic relative abundances are higher in the second case, but, due to the combined effect of stellar temperature and luminosity, as well as of the density, t² of the analysed objects are not high. Consequently, the difference in the ionic abundance determination by the two methods are less than 20%, except for S⁺ ions, for which the deviation can reach 40%.