Talk abstract details

Based on time-dependent radiation-hydrodynamics simulations of the evolution
of Planetary Nebulae (PNe), we have carried out a systematic parameter study
to address the non-trivial question of how the diffuse X-ray emission of
PNe with closed central cavities depends on the evolutionary state of the
nebula, the mass of the central star, and the chemical composition of the
stellar wind and circumstellar matter.

Given the radial temperature / density structure of the spherically symmetric
hydrodynamical model, we use the Chianti code to compute the emergent X-ray
spectrum, the X-ray luminosity, and the wavelength-dependent surface
brightness distribution of the hot central cavity. For hydrogen-rich
composition, the models predict the highest X-ray luminosity for metal-rich
nebulae with massive and hot central stars. Preliminary test calculations
indicate that Planetary Nebula with a Wolf-Rayet type central star can reach
even higher X-ray luminosities.

In general, the model predictions depend critically on whether or not
thermal conduction at the interface between the central "hot bubble"
and the inner nebula is taken into account. Quantitative comparison
of the model results with available X-ray observations indicates that
thermal conduction plays an important role in controlling the temperature
structure and X-ray emission of the central cavity.

Our grid of models may be used to interpret observed correlations (e.g.\
between X-ray temperature and bubble radius), and to estimate whether or not
a given PN is detectable by present-day / future X-ray observatories.