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J.H. Kastner (Rochester Institute of Technology), N. Soker (Department of Physics, Oranim, Tivon, Israel), J. Li (Rochester Institute of Technology), S. Vrtilek (Harvard-Smithsonian Center for Astrophysics)
X-ray emission from planetary nebulae (PNs) is expected to arise in shocks at the interface between a wind from the PN core (or a companion) and material ejected when the progenitor was on the asymptotic giant branch (AGB). Extended X-ray emission, if present, therefore likely traces the very processes responsible for sculpting PNs. The Chandra X-ray Observatory (CXO) and XMM-Newton, with their powerful combinations of spatial and spectral resolution, are providing new insight into these shaping processes, as well as other fundamental aspects of PNs. We review some of these recent results. Energy-resolved CXO imaging demonstrates that intranebular extinction can modulate the X-ray surface brightnesses of young, dusty PNs, although this imaging also suggests that the action of collimated outflows and/or heat conduction may play important roles in determining X-ray morphologies. The potential importance of collimated outflows and binary companions is emphasized by other X-ray imaging results, as well. The X-ray luminosity evolution and relatively low X-ray emission temperatures of the PNs observed to date by CXO and XMM indicate that the extended emission may result from a post-AGB, pre-PN wind driven by the central star or a companion; such outflows are notoriously non-spherical. Meanwhile, CXO's discovery of compact X-ray sources at the cores of at least two PNs suggests that some nebulae harbor late-type main sequence stars with bright coronae. Such stars likely have been spun up and, hence, become magnetically active, via accretion of wind material from the mass-losing PN core.
J.H.K. and J.L. acknowledge support for this research provided by NASA/CXO grants GO0--1067X and G02--3009X to RIT. N.S. acknowledges support from the US-Israel Binational Science Foundation.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.