Heat conduction has been found a plausible solution to explain discrepancies
between expected and measured temperatures in hot bubbles of planetary nebulae
(PNe). While the heat conduction process depends on the chemical composition,
to date it has been exclusively studied for pure hydrogen plasmas in PNe. A
smaller population of PNe show hydrogen-deficient and helium- and
carbon-enriched surfaces surrounded by bubbles of the same composition;
considerable differences are expected in physical properties of these objects
in comparison to the pure hydrogen case. The aim of this study is to explore
how a chemistry-dependent formulation of the heat conduction affects physical
properties and how it affects the X-ray emission from PN bubbles of
hydrogen-deficient stars. We extend the description of heat conduction in our
radiation hydrodynamics code to work with any chemical composition. We then
compare the bubble-formation process with a representative PN model using both
the new and the old descriptions. We also compare differences in the resulting
X-ray temperature and luminosity observables of the two descriptions. The
improved equations show that the heat conduction in our representative model of
a hydrogen-deficient PN is nearly as efficient with the chemistry-dependent
description; a lower value on the diffusion coefficient is compensated by a
slightly steeper temperature gradient. The bubble becomes somewhat hotter with
the improved equations, but differences are otherwise minute. The observable
properties of the bubble in terms of the X-ray temperature and luminosity are
seemingly unaffected.Comment: 11 pages, 11 figures, A&A in pres
