SIMBAD references

2007A&A...475..619C - Astronomy and Astrophysics, volume 475, 619-627 (2007/11-4)

Asteroseismological constraints on the coolest GW Virginis variable star (PG 1159-type) PG 0122+200.


Abstract (from CDS):

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 (2006A&A...454..845M). We perform extensive computations of adiabatic g-mode pulsation periods on PG 1159 evolutionary models with stellar masses ranging from 0.530 to 0.741M. 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. We derive a stellar mass of 0.626M from a comparison between the observed period spacing and the computed asymptotic period spacing, and a stellar mass of 0.567M 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 <δΠi≥0.88s and a root-mean-square residual of σδΠi=1.27s. The model has an effective temperature Teff=81500K, a stellar mass M*=0.556M, a surface gravity logg=7.65, a stellar luminosity and radius of log(L*/L)=1.14 and log(R*/R)=-1.73, respectively, and a He-rich envelope thickness of Menv=1.9x10–2M. We derive a seismic distance d∼614pc and a parallax π∼1.6mas. 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.

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Journal keyword(s): stars: evolution - stars: interiors - stars: oscillations - stars: variables: general - stars: white dwarfs

Simbad objects: 6

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