2007A&A...461.1095C

We present asteroseismological inferences on RXJ2117.1+3412, the hottest known pulsating PG1159 star. Our results are based on full PG1159 evolutionary models recently presented by Miller Bertolami & Althaus (2006A&A...454..845M). We performed extensive computations of adiabatic g-mode pulsation periods on PG1159 evolutionary models with stellar masses ranging from 0.530 to 0.741M_☉. PG1159 stellar models are extracted from the complete evolution of progenitor stars started from the ZAMS, through the thermally pulsing AGB and born-again phases to the domain of the PG1159 stars. We constrained the stellar mass of RXJ2117.1+3412 by comparing the observed period spacing with the asymptotic period spacing and with the average of the computed period spacings. We also employed the individual observed periods to find a representative seismological model for RXJ2117.1+3412.We derive a stellar mass M_*∼0.56-0.57M_☉ from the period spacing data alone. In addition, we found a best-fit model representative for RXJ2117.1+3412 with an effective temperature T_eff=163400K, a stellar mass M_*=0.565M_☉, and a surface gravity logg=6.61. The derived stellar luminosity and radius are log (L_*/L_☉)=3.36 and log(R_*/R_☉)=-1.23, respectively, and the He-rich envelope thickness is M_env=0.02M_☉. We derive a seismic distance d∼452pc and a linear size of the planetary nebula D_PN∼1.72pc. These inferences seem to solve the discrepancy between the RXJ2117.1+3412 evolutionary timescale and the size of the nebula. All of the seismological tools we use concur to the conclusion that RXJ2117.1+3412 must have a stellar mass M_*∼0.565M_☉, much in agreement with recent asteroseismology studies and in clear conflict with the predictions of spectroscopy plus evolutionary tracks.