Chemically inhomogeneous photoionization modelling of the planetary   nebula SMC N87
  We present results from dual-abundance photoionization modelling of the planetary nebula SMC N87 (SMC-SMP 27). The models succesfully resolve the observed discrepancy between the heavy-element abundances derived semiempirically from the optical recombination lines and the collisionally excited lines, incorporating a H-poor gaseous component in the main body of the PN. The mass of the H-poor plasma is only about 1 per cent of the total PN ionized mass and its electron temperature is 6300 K. The average heavy element abundances in the PN approximate those returned by the ICF method using the collisionally excited lines (for t^2 = 0), while the He abundance is less than the one found empirically. The C/O ratio in the H-depleted component is smaller than in the normal metallicity gas, in contrast to stellar nucleosynthetic models which predict the opposite for processed material ejected from an evolved PN nucleus. 
Y. G. Tsamis and D. Pequignot (Observatoire de Paris - Meudon)