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Issue A&A Volume 378, Number 2, November I 2001 Page(s) 587 - 596 Section Stellar clusters and associations DOI 10.1051/0004-6361:20011172

A&A 378, 587-596 (2001)
DOI: 10.1051/0004-6361:20011172

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

S. Hyung¹, G. Mellema², S.-J. Lee³ and H. Kim<sup>4

1</sup>  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

(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. (2001) 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.

Key words: hydrodynamics -- stars: AGB and post-AGB -- stars: winds, outflows -- ISM: kinematics and dynamics -- planetary nebulae: individual: NGC 6543

Offprint request: G. Mellema, mellema@strw.leidenuniv.nl

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