Letter to the Editor
Diffuse X-ray emission from the planetary nebula NGC 7009*
Astronomy Department, University of Illinois, 1002 W. Green Street, Urbana, IL 61801, USA
Corresponding author: M. A. Guerrero, email@example.com
Accepted: 1 March 2002
XMM-Newton EPIC observations of the planetary nebula (PN) NGC 7009, the Saturn Nebula, have detected extended X-ray emission in its central cavity. The diffuse X-ray emission must originate in the shocked fast stellar wind. The spectra show that the temperature of the hot gas is K. The rms density derived from the volume emission measure is a few tens H-atom cm-3. The hot gas does not appear over-pressurized with respect to the nebular shell. NGC 7009 represents an evolutionary stage at which the influence of the hot gas in the PN interior starts to decline due to the diminishing strength of the fast stellar wind and the expansion of the central cavity.
Key words: ISM: planetary nebulae: general / ISM: planetary nebulae: individual: NGC 7009 / stars: winds, outflows / X-rays: ISM
© ESO, 2002