Echelle measurements of the electron temperature of the giant halo of the planetary nebula NGC 6543

Abstract

Observations with the Manchester echelle spectrometer, of spatially resolved profiles of the Hα, [N II] and [O III] lines from a bright knot in the halo of NGC 6543 yield an electron temperature of |$T_\text e = 8860 \pm 1000$| K. This seemingly contradicts a previous measurement of |$T_\text e = 14\enspace 700 \pm 850$| K from the [O III] (5007 Å/4363 Å) line intensity ratio for exactly the same area of the halo which is 6000 K higher than that given for the nebular core by the same line ratio method. A model in which flows of ‘mass-loaded’ stellar wind form bow shocks around halo clumps is presented in an attempt to explain this apparent discrepancy in the values of Te for the halo of NGC 6543 that is found between the profile and ratio methods. The model is also substantiated by observations of the relative positions of the small-scale features of the Hα, [N II] and [O III] emission regions.