[N II] and [O III] mean electron temperatures in planetary nebulae

Mean electron temperatures for 106 planetary nebulae are presented, which have been derived using calculations of the values of electron temperature-sensitive line ratios involving forbidden transitions among the 2s² 2p^{2 3}P, ¹D, and ¹S levels of N⁺ and O⁺⁺, based on new electron impact rates and transition probabilities. Comparison of these results with values of T_e [N II] and T_e [O III] determined previously by Kaler reveals that the present electron temperatures are systematically lower for both ions, and that this discrepancy is correlated with the electron density in the nebula. It is also shown that the average difference between T_e [N II] and T_e [O III] in a planetary nebula is somewhat smaller than that derived by Kaler, with the present results implying that the N II and O III temperatures disagree on average by 2070 K as opposed to the 2210 K average found by Kaler.