The electron temperature of the inner halo of the Planetary Nebula NGC 6543

Abstract

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 [O Iii] filters. Balick et al. (\cite{Balick01}) showed that the inner halo consists of a number of spherical shells. We find the temperature of this inner halo to be much higher ( ~ 15 000 K) than that of the bright core nebula ( ~ 8500 K). 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.