SIMBAD references

I have systematically compared the period spectra of pre-white dwarf evolutionary models to the observed period spectra of the variable PG 1159 stars. I find that no model simultaneously matches both the observed period spacing (considered the primary diagnostic of the stellar mass) and the period offset for any pulsating pre-white dwarf star over its spectroscopically constrained temperature range. I discuss implications for previously published asteroseismological mass and distance measurements. Finally, I outline a simple physical interpretation of the problem and suggest possible avenues to pursue the cause of the difficulty.