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Y.-H. Chu, M.A. Guerrero, R.A. Gruendl, J.B. Kaler (UIUC), R.M. Williams (NASA/GSFC)
The Cat's Eye Nebula, also known as NGC~6543, has perhaps the most intriguing and complex morphology among planetary nebulae (PNe). It is a known X-ray source, but previous observations were unable to resolve the distribution of the X-rays. Recent Chandra ACIS-S observations of the Cat's Eye clearly resolved the X-ray emission into a point source at the central star and diffuse emission confined within the central elliptical shell and two lobes along the major axis. Analyses of the spectra of the central shell and the two lobes show that the hot gas in the Cat's Eye has temperatures of ~1.6\times106 K and that its abundances are similar to those of the fast stellar wind and not those of the nebula. The spectral variations among these regions can be explained by different amounts of absorption through the nebula along the line of sight.
It is puzzling that the X-ray-emitting gas appears to be comprised of mostly stellar wind material yet its temperature is much lower than expected for an adiabatically shocked stellar wind. Extremely efficient cooling mechanisms are needed. The study of X-ray emission from the Cat's Eye will help us understand why most PNe do not have detectable diffuse X-ray emission, and thus provide insights on the formation and evolution of PNe.
This work is supported by the CXC grant number GO0-1004X.
The author(s) of this abstract have provided an email address for comments about the abstract: chu@astro.uiuc.edu