Bibcode
Costa, J. E. S.; Kepler, S. O.; Winget, D. E.; O'Brien, M. S.; Kawaler, S. D.; Costa, A. F. M.; Giovannini, O.; Kanaan, A.; Mukadam, A. S.; Mullally, F.; Nitta, A.; Provençal, J. L.; Shipman, H.; Wood, M. A.; Ahrens, T. J.; Grauer, A.; Kilic, M.; Bradley, P. A.; Sekiguchi, K.; Crowe, R.; Jiang, X. J.; Sullivan, D.; Sullivan, T.; Rosen, R.; Clemens, J. C.; Janulis, R.; O'Donoghue, D.; Ogloza, W.; Baran, A.; Silvotti, R.; Marinoni, S.; Vauclair, G.; Dolez, N.; Chevreton, M.; Dreizler, S.; Schuh, S.; Deetjen, J.; Nagel, T.; Solheim, J.-E.; Gonzalez Perez, J. M.; Ulla, A.; Barstow, M.; Burleigh, M.; Good, S.; Metcalfe, T. S.; Kim, S.-L.; Lee, H.; Sergeev, A.; Akan, M. C.; Çakırlı, Ö.; Paparo, M.; Viraghalmy, G.; Ashoka, B. N.; Handler, G.; Hürkal, Ö.; Johannessen, F.; Kleinman, S. J.; Kalytis, R.; Krzesinski, J.; Klumpe, E.; Larrison, J.; Lawrence, T.; Meištas, E.; Martinez, P.; Nather, R. E.; Fu, J.-N.; Pakštienė, E.; Rosen, R.; Romero-Colmenero, E.; Riddle, R.; Seetha, S.; Silvestri, N. M.; Vučković, M.; Warner, B.; Zola, S.; Althaus, L. G.; Córsico, A. H.; Montgomery, M. H.
Bibliographical reference
Astronomy and Astrophysics, Volume 477, Issue 2, January II 2008, pp.627-640
Advertised on:
1
2008
Journal
Citations
54
Refereed citations
37
Description
Context: PG 1159-035, a pre-white dwarf with
Teff≃ 140 000 K, is the prototype of both two classes:
the PG 1159 spectroscopic class and the DOV pulsating class. Previous
studies of PG 1159-035 photometric data obtained with
the Whole Earth Telescope (WET) showed a rich frequency spectrum
allowing the identification of 122 pulsation modes. Analyzing the
periods of pulsation, it is possible to measure the stellar mass, the
rotational period and the inclination of the rotation axis, to estimate
an upper limit for the magnetic field, and even to obtain information
about the inner stratification of the star. Aims: We have three
principal aims: to increase the number of detected and identified
pulsation modes in PG 1159-035, study trapping of the
star's pulsation modes, and to improve or constrain the determination of
stellar parameters. Methods: We used all available WET
photometric data from 1983, 1985, 1989, 1993 and 2002 to identify the
pulsation periods. Results: We identified 76 additional
pulsation modes, increasing to 198 the number of known pulsation modes
in PG 1159-035, the largest number of modes detected
in any star besides the Sun. From the period spacing we estimated a mass
M/M_&sun; = 0.59 ± 0.02 for PG 1159-035, with
the uncertainty dominated by the models, not the observation. Deviations
in the regular period spacing suggest that some of the pulsation modes
are trapped, even though the star is a pre-white dwarf and the
gravitational settling is ongoing. The position of the transition zone
that causes the mode trapping was calculated at r_c/R_star = 0.83
± 0.05. From the multiplet splitting, we calculated the
rotational period P_rot = 1.3920 ± 0.0008 days and an upper limit
for the magnetic field, B < 2000 G. The total power of the pulsation
modes at the stellar surface changed less than 30% for ℓ = 1 modes
and less than 50% for ℓ = 2 modes. We find no evidence of linear
combinations between the 198 pulsation mode frequencies. PG
1159-035 models have not significative convection zones,
supporting the hypothesis that nonlinearity arises in the convection
zones in cooler pulsating white dwarf stars.
Tables [see full textsee full text]-[see full textsee full text] are
only available in electronic form at http://www.aanda.org
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