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# Asteroseismology of RXJ 2117+3412, the hottest pulsating PG 1159 star

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Jagiellonian University, Cracovia, Lesser Poland Voivodeship, Poland
(Impact Factor: 4.38). 01/2002; 381(1). DOI: 10.1051/0004-6361:20011483

ABSTRACT

The pulsating PG 1159 planetary nebula central star RXJ 2117+3412 has been observed over three successive seasons of a multisite photometric campaign. The asteroseismological analysis of the data, based on the 37 identified $\ell=1$ modes among the 48 independent pulsation frequencies detected in the power spectrum, leads to the derivation of the rotational splitting, the period spacing and the mode trapping cycle and amplitude, from which a number of fundamental parameters can be deduced. The average rotation period is $1.16\pm 0.05$ days. The trend for the rotational splitting to decrease with increasing periods is incompatible with a solid body rotation. The total mass is 0.56$^{+0.02}_{-0.04}$ $M_{\odot}$ and the He-rich envelope mass fraction is in the range 0.013–0.078 $M_{*}$. The luminosity derived from asteroseismology is log($L/L_{\odot})= 4.05$ $^{+0.23}_{-0.32}$ and the distance 760 $^{+230}_{-235}$ pc. At such a distance, the linear size of the planetary nebulae is $2.9\pm 0.9$ pc. The role of mass loss on the excitation mechanism and its consequence on the amplitude variations is discussed.

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Available from: J. N. Fu, Oct 01, 2015
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ABSTRACT: We have acquired new time series photometry of the two pulsating DB white dwarf stars KUV 05134+2605 and PG 1654+160 with the Whole Earth Telescope. Additional single-site photometry is also presented. We use all these data plus all available archival measurements to study the temporal behaviour of the pulsational amplitudes and frequencies of these stars for the first time. We demonstrate that both KUV 05134+2605 and PG 1654+160 pulsate in many modes, the amplitudes of which are variable in time; some frequency variability of PG 1654+160 is also indicated. Beating of multiple pulsation modes cannot explain our observations; the amplitude variability must therefore be intrinsic. We cannot find stable modes to be used for determinations of the evolutionary period changes of the stars. Some of the modes of PG 1654+160 appear at the same periods whenever detected. The mean spacing of these periods (≈40 s) suggests that they are probably caused by non-radial gravity-mode pulsations of spherical degree ℓ= 1. If so, PG 1654+160 has a mass around 0.6 M⊙. The time-scales of the amplitude variability of both stars (down to two weeks) are consistent with theoretical predictions of resonant mode coupling, a conclusion which might however be affected by the temporal distribution of our data.
Monthly Notices of the Royal Astronomical Society 03/2003; 340(3):1031 - 1038. DOI:10.1046/j.1365-8711.2003.06373.x · 5.11 Impact Factor
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##### Article: Abell 43, a second pulsating hybrid-PG 1159'' star
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ABSTRACT: We report observations of the planetary nebula nucleus Abell 43, obtained at the 2.5 m Nordic Optical Telescope, which show that it is a pulsator. Abell 43, a “hybrid-PG 1159” type star, is the second pulsator of this class, after HS 2324+3944. From the limited data set acquired, we find that Abell 43 exhibits at least two periods of 2600 s and 3035 s, the longest ones observed up to now in PG 1159 and “hybrid-PG 1159” pulsators. This strongly suggests that the variations are due to non-radial g-mode pulsations and cannot be a consequence of binarity. This discovery raises puzzling questions regarding the excitation mechanism in this H rich, C and O poor “hybrid-PG 1159” since the C and O abundances are too low to trigger the instability through the κ-mechanism induced by the partial ionization of C and O, a mechanism invoked to explain the instability in the PG 1159 stars and in the previously known “hybrid-PG 1159” pulsator HS 2324+3944.
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