2001A&A...378..587H

We investigate the electron temperature of the inner halo and nebular core regions of NGC 6543, using archival Hubble Space Telescope ( HST) Wide Field Planetary Camera 2 (WFPC2) images taken through narrow band [OIII] filters. Balick et al. (2001AJ....121..354B) showed that the inner halo consists of a number of spherical shells. We find the temperature of this inner halo to be much higher (∼15000K) than that of the bright core nebula (∼8500K). Photo-ionization models indicate that hardening of the UV radiation from the central star cannot be the main source of the higher temperature in the halo region. Using a radiation hydrodynamic simulation, we show that mass loss and velocity variations in the AGB wind can explain the observed shells, as well as the higher electron temperature.