TEMPERATURE-FLUCTUATIONS IN PLANETARY-NEBULAE

Theoretical temperature fluctuations (t(2)) are obtained for typical p lanetary nebula conditions. Results are given for the temperature fluc tuation of the most commonly observed ions (H+, N+, O+, O++, Ne++, S+, and S++). Since the results show that t(2) is more important for plan etary nebulae (PNe) with high stellar temperatures, we discuss some ob served PNe with stellar temperature greater than 100 000 K. For these objects, the ionic abundances relative to H+ are calculated with and w ithout 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, t(2) of the analysed objects are not high. Con sequently, the difference in the ionic abundance determination by the two methods are less than 20%, except for S+ ions, for which the devia tion can reach 40%.