Pumping Up the [N I] Nebular Lines

  title={Pumping Up the [N I] Nebular Lines},
  author={G. J. Ferland and W. J. Henney and C. R. O’Dell and Ryan Lucian Porter and Peter Andreas Maria van Hoof and R. J. R. Williams Kentucky CRyA and Unam and Mexico Vanderbilt Royal Observatory of Belgium Awe Aldermaston and UK.},
  journal={The Astrophysical Journal},
The optical [Ni] doublet near 5200 A is anomalously strong in a variety of emission-line objects. We compute a detailed photoionization model and use it to show that pumping by far-ultraviolet (FUV) stellar radiation previously posited as a general explanation applies to the Orion Nebula (M42) and its companion M43; but, it is unlikely to explain planetary nebulae and supernova remnants. Our models establish that the observed nearly constant equivalent width of [Ni] with respect to the dust… 
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