N-III LINE EMISSION IN PLANETARY-NEBULAE - CONTINUUM FLUORESCENCE

Kastner & Bhatia have recently pointed out that the optical "Bowen" N III emission lines are not produced by Bowen fluorescence in a sample of planetary nebulae. Here I point out that the lines are likely to be excited by direct continuum fluorescence. Photoionization model calculations with an improved treatment of line-continuum fluorescence are presented. The predicted intensity of N III lambda-4634 is in good agreement with observations. This line can be used as a direct probe of the stellar continuum in the lambda approximately 374 angstrom region, and may provide an important test of the next generation of model stellar atmospheres.