Characteristic X-ray temperature T_X (top panel) and X-ray luminosity L_X (bottom panel) for a suite of chemically stratified heat-conduction bubbles constructed from pure WR ZP96 models that comply with both the observed oxygen and neon line ratios of BD +30 (crosses in Fig. 8) versus ω = M_PN∕(M_PN + M_WR). The thick line corresponds to the model sequence originating from the 500-yr old “best-fit” WR-model. We note the break of the abscissa scale at ω = 0.05. The wavelength range considered is 5–40 Å (0.3–2.5 keV.)