Volume 475, Number 2, November IV 2007
|Page(s)||619 - 627|
|Section||Stellar structure and evolution|
|Published online||24 September 2007|
Asteroseismological constraints on the coolest GW Virginis variable star (PG 1159-type) PG 0122+200
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, Argentina
3 Université Paul Sabatier, Observatoire Midi-Pyrénées, CNRS/UMR5572, 14 Av. Belin, 31400 Toulouse, France e-mail: firstname.lastname@example.org
4 Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany e-mail: email@example.com
Accepted: 29 August 2007
Aims.We present an asteroseismological study of PG 0122+200, the coolest known pulsating PG 1159 (GW Vir) star. Our results are based on an augmented set of the full PG 1159 evolutionary models recently presented by Miller Bertolami & Althaus (2006).
Methods.We perform extensive computations of adiabatic g-mode pulsation periods on PG 1159 evolutionary models with stellar masses ranging from 0.530 to 0.741 . These models take into account the complete evolution of progenitor stars, through the thermally pulsing asymptotic giant branch phase and born-again episode. We constrain the stellar mass of PG 0122+200 by comparing the observed period spacing with the asymptotic period spacing and with the average of the computed period spacings. We also employ the individual observed periods to find a representative seismological model for PG 0122+200.
Results.We derive a stellar mass of 0.626 from a comparison between the observed period spacing and the computed asymptotic period spacing, and a stellar mass of 0.567 by comparing the observed period spacing with the average of the computed period spacing. We also find, on the basis of a period-fit procedure, an asteroseismological model representative of PG 0122+200 that is able to reproduce the observed period pattern with an average of the period differences of = 0.88 s and a root-mean-square residual of = 1.27 s. The model has an effective temperature = 81 500 K, a stellar mass = 0.556 , a surface gravity log g = 7.65, a stellar luminosity and radius of = 1.14 and = -1.73, respectively, and a He-rich envelope thickness of Menv = 1.9 10-2 . We derive a seismic distance d ~ 614 pc and a parallax π ~ 1.6 mas. The results of the period-fit analysis carried out in this work suggest that the asteroseismological mass of PG 0122+200 could be ~6-20% lower than hitherto thought, and in closer agreement (to within ~5%) with the spectroscopic mass. This result suggests that a reasonable consistency between the stellar mass values obtained from spectroscopy and asteroseismology can be expected when detailed PG 1159 evolutionary models are considered.
Key words: stars: evolution / stars: interiors / stars: oscillations / stars: variables: general / stars: white dwarfs
© ESO, 2007
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.