Normal modes and discovery of high-order cross-frequencies in the DBV white dwarf GD 358

Vuille, François; O’Donoghue, D.; Buckley, D.; Massacand, C. M.; Solheim, J. E.; Bard, S.; Vauclair, G.; Giovannini, O.; Kepler, S. O.; Kanaan, A.; Provencal, J. L.; Wood, M. A.; Clemens, J. C.; Kleinman, S. J.; O'Brien, M. S.; Nather, R. E.; Winget, D. E.; Nitta, A.; Klumpe, E. W.; Montgomery, M. H.; Watson, T. K.; Bradley, P. A.; Sullivan, D. J.; Wu, Kinwah; Marar, T. M. K.; Seetha, S.; Ashoka, B. N.; Mahra, H. S.; Bhat, Bratati; Babu, V. C.; Leibowitz, E. M.; Hemar, Shirley; Ibbetson, P.; Mashals, E.; Meistas, E.; Moskalik, P.; Zoła, S.; Krzesiński, Jurek; Pajdosz, G.

doi:10.1046/j.1365-8711.2000.03369.x

Cited by 33 publications

(16 citation statements)

References 15 publications

(23 reference statements)

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“…It is therefore essential that combination frequencies are correctly recognized in the amplitude spectra of pulsating white dwarf stars. Vuille et al (2000) pointed out a similar problem in their study of the prototype pulsating DB white dwarf star GD 358. However, there are some differences between our results and those of Vuille et al (2000): the third-order combination frequencies revealed in their work only manifested themselves as 'odd' peaks lying close to or within rotationally split multiplets, and those authors could explain all of those 'odd' peaks with combination frequencies.…”

Section: The Third-order Combination Frequenciesmentioning

confidence: 91%

“…Vuille et al (2000) pointed out a similar problem in their study of the prototype pulsating DB white dwarf star GD 358. However, there are some differences between our results and those of Vuille et al (2000): the third-order combination frequencies revealed in their work only manifested themselves as 'odd' peaks lying close to or within rotationally split multiplets, and those authors could explain all of those 'odd' peaks with combination frequencies. In our case, the third-order combinations create apparent additional frequency multiplets, and we found signals within the rotationally split normal-mode multiplets that we were unable to explain by combination frequencies; we suspect they are artefacts caused by amplitude/frequency variations during the measurements.…”

Section: The Third-order Combination Frequenciesmentioning

confidence: 91%

“…An important fact about the second type of combination signals is that their frequencies are in the same range as those of the independent signals (see also Vuille et al 2000). Consequently, they may be mistaken for independent frequencies if not systematically searched for.…”

Section: The Third-order Combination Frequenciesmentioning

confidence: 99%

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The pulsating DA white dwarf star EC 14012−1446: results from four epochs of time-resolved photometry

Handler

Romero-Colmenero

Provençal

et al. 2008

Monthly Notices of the Royal Astronomical Society

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The pulsating DA white dwarfs are the coolest degenerate stars that undergo self‐driven oscillations. Understanding their interior structure will help us to understand the previous evolution of the star. To this end, we report the analysis of more than 200 h of time‐resolved CCD photometry of the pulsating DA white dwarf star EC 14012−1446 acquired during four observing epochs in three different years, including a coordinated three‐site campaign. A total of 19 independent frequencies in the star's light variations together with 148 combination signals up to fifth order could be detected. We are unable to obtain the period spacing of the normal modes and therefore a mass estimate of the star, but we infer a fairly short rotation period of 0.61 ±0.03 d, assuming the rotationally split modes are ℓ= 1. The pulsation modes of the star undergo amplitude and frequency variations, in the sense that modes with higher radial overtone show more pronounced variability and that amplitude changes are always accompanied by frequency variations. Most of the second‐order combination frequencies detected have amplitudes that are a function of their parent mode amplitudes, but we found a few cases of possible resonantly excited modes. We point out the complications in the analysis and interpretation of data sets of pulsating white dwarfs that are affected by combination frequencies of the form fA+fB−fC intruding into the frequency range of the independent modes.

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Section: The Third-order Combination Frequenciesmentioning

confidence: 91%

Section: The Third-order Combination Frequenciesmentioning

confidence: 91%

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The pulsating DA white dwarf star EC 14012−1446: results from four epochs of time-resolved photometry

Handler

Romero-Colmenero

Provençal

et al. 2008

Monthly Notices of the Royal Astronomical Society

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“…The examination of these problems can be aided by asteroseismology -the study of the interiors of pulsating stars via the analysis of their normal-mode spectra. Fortunately, a class of pulsating DB white dwarf stars (hereinafter DBVs) exists, and their prototype, GD 358, is one of the classical examples for the successful appli-E-mail: handler@astro.univie.ac.at cation of asteroseismological methods Vuille et al 2000).…”

Section: Introductionmentioning

confidence: 99%

The asteroseismological potential of the pulsating DB white dwarf stars CBS 114 and PG 1456+103

Handler

Metcalfe

Wood

2002

Monthly Notices of the Royal Astronomical Society

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We have acquired 65 h of single‐site time‐resolved CCD photometry of the pulsating DB white dwarf star (DBV) CBS 114 and 62 h of two‐site high‐speed CCD photometry of another DBV, PG 1456+103. The pulsation spectrum of PG 1456+103 is complicated and variable on time‐scales of approximately 1 week and could only partly be deciphered with our measurements. The modes of CBS 114 are more stable in time and we were able to arrive at a frequency solution somewhat affected by aliasing, but still satisfactory, involving seven independent modes and two combination frequencies. These frequencies also explain the discovery data of the star, taken 13 yr earlier. We find a mean period spacing of 37.1 ± 0.7 s significant at the 98 per cent level between the independent modes of CBS 114 and argue that they are caused by non‐radial g‐mode pulsations of spherical degree ℓ= 1. We performed a global search for asteroseismological models of CBS 114 using a genetic algorithm, and we examined the susceptibility of the results to the uncertainties of the observational frequency determinations and mode identifications (we could not provide m values). The families of possible solutions are identified correctly even without knowledge of m. Our best‐fitting model suggests Teff= 21 000 K, M*= 0.730 M⊙ and log(MHe/M*) =−6.66, XO= 0.61. The latter value of the central oxygen mass fraction implies a rate for the 12C(α,γ)16O nuclear reaction near S300= 180 keV b, consistent with laboratory measurements.

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“…A comparison of the individual mode periods of the known = 1 pulsator GD 358 (Winget et al 1994;Vuille et al 2000) and those of another DBV, CBS 114 (Handler et al 2002), with that of PG 1654+160 also supports this interpretation. However, the number of available observed modes of PG 1654+160 is insufficient for seismic model calculations, and the uncertainties of their periods are too large.…”

Section: Discussionmentioning

confidence: 83%

Amplitude and frequency variability of the pulsating DB white dwarf stars KUV 05134+2605 and PG 1654+160 observed with the Whole Earth Telescope

Handler¹,

O’Donoghue²,

Müller³

et al. 2003

Monthly Notices of the Royal Astronomical Society

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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.

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Normal modes and discovery of high-order cross-frequencies in the DBV white dwarf GD 358

Cited by 33 publications

References 15 publications

The pulsating DA white dwarf star EC 14012−1446: results from four epochs of time-resolved photometry

The pulsating DA white dwarf star EC 14012−1446: results from four epochs of time-resolved photometry

The asteroseismological potential of the pulsating DB white dwarf stars CBS 114 and PG 1456+103

Amplitude and frequency variability of the pulsating DB white dwarf stars KUV 05134+2605 and PG 1654+160 observed with the Whole Earth Telescope

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