Asteroseismological constraints on the pulsating planetary nebula nucleus (PG 1159-type) RX J2117.1+3412

¹ Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque S/N, (1900) La Plata, Argentina e-mail: [acorsico;althaus;mmiller]@fcaglp.unlp.edu.ar
² Instituto de Astrofísica La Plata, IALP, CONICET-UNLP
³ Max-Planck-Institut für Astrophysik, Garching, Germany
⁴ Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany e-mail: werner@astro.uni-tuebingen.de

Received: 26 September 2006
Accepted: 12 October 2006

Abstract

Aims.We present asteroseismological inferences on RX J2117.1+3412, the hottest known pulsating PG 1159 star. Our results are based on full PG 1159  evolutionary models recently presented by Miller Bertolami & Althaus (2006).

Methods.We performed extensive computations of adiabatic g-mode pulsation periods on PG 1159 evolutionary models with stellar masses ranging from 0.530 to . PG 1159 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 PG 1159 stars. We constrained the stellar mass of RX J2117.1+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 RX J2117.1+3412.

Results.We derive a stellar mass from the period spacing data alone. In addition, we found a best-fit model representative for RX J2117.1+3412 with an effective temperature  K, a stellar mass , and a surface gravity . The derived stellar luminosity and radius are and , respectively, and the He-rich envelope thickness is . We derive a seismic distance  pc and a linear size of the planetary nebula  pc. These inferences seem to solve the discrepancy between the RX J2117.1+3412 evolutionary timescale and the size of the nebula. All of the seismological tools we use concur to the conclusion that RX J2117.1+3412 must have a stellar mass , much in agreement with recent asteroseismology studies and in clear conflict with the predictions of spectroscopy plus evolutionary tracks.