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

¹ Korea Astronomy Observatory, 61-1 Whaam-dong, Yusong-gu, Taejon 305-348, Korea e-mail: hyung@kao.re.kr
² Sterrewacht Leiden, PO Box 9513, 2300 RA, Leiden, The Netherlands e-mail: mellema@strw.leidenuniv.nl
³ Dept. of Astronomy and Space Science, Chungnam National University, 220 Kung-dong, Yusong-gu, Taejon 305-764, Korea e-mail: seong@canopus.chungnam.ac.kr
⁴ Dept. of Earth Science Education, Korea National University of Education, Chung-Buk 363-791, Korea e-mail: vitkim@kao.re.kr

Corresponding author: G. Mellema, mellema@strw.leidenuniv.nl

Received: 14 June 2001
Accepted: 16 August 2001

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 [Oiii] filters. Balick et al. ([CITE]) 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.