Whole Earth Telescope observations of the hot helium atmosphere pulsating white dwarf EC 20058-5234

D. J. Sullivan, T. S. Metcalfe, D. O'Donoghue, D. E. Winget, D. Kilkenny, F. Van Wyk, A. Kanaan, S. O. Kepler, A. Nitta, S. D. Kawaler, M. H. Montgomery, R. E. Nather, M. S. O'Brien, Agnes Kim, M. Wood, X. J. Jiang, E. M. Leibowitz, P. Ibbetson, S. Zola, J. KrzesinskiG. Pajdosz, G. Vauclair, N. Dolez, M. Chevreton

Research output: Contribution to journalArticle

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Abstract

We present the analysis of a total of 177 h of high-quality optical time-series photometry of the helium atmosphere pulsating white dwarf (DBV) EC 20058-5234. The bulk of the observations (135 h) were obtained during a WET campaign (XCOV15) in 1997 July that featured coordinated observing from four southern observatory sites over an 8-d period. The remaining data (42 h) were obtained in 2004 June at Mt John Observatory in NZ over a one-week observing period. This work significantly extends the discovery observations of this low-amplitude (few per cent) pulsator by increasing the number of detected frequencies from 8 to 18, and employs a simulation procedure to confirm the reality of these frequencies to a high level of significance (1 in 1000). The nature of the observed pulsation spectrum precludes identification of unique pulsation mode properties using any clearly discernable trends. However, we have used a global modelling procedure employing genetic algorithm techniques to identify the n, ℓ values of eight pulsation modes, and thereby obtain asteroseismic measurements of several model parameters, including the stellar mass (0.55 M ) and T eff (∼28 200 K). These values are consistent with those derived from published spectral fitting: T eff ∼ 28 400 K and log g ∼ 7.86. We also present persuasive evidence from apparent rotational mode splitting for two of the modes that indicates this compact object is a relatively rapid rotator with a period of 2 h. In direct analogy with the corresponding properties of the hydrogen (DAV) atmosphere pulsators, the stable low-amplitude pulsation behaviour of EC 20058 is entirely consistent with its inferred effective temperature, which indicates it is close to the blue edge of the DBV instability strip. Arguably, our most significant result from this work is the clear demonstration that EC 20058 is a very stable pulsator with several dominant pulsation modes that can be monitored for their long-term stability.

Original languageEnglish (US)
Pages (from-to)137-152
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Volume387
Issue number1
DOIs
StatePublished - Jun 1 2008

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helium
observatory
telescopes
atmospheres
atmosphere
genetic algorithm
hydrogen
time series
observatories
modeling
simulation
stellar mass
genetic algorithms
temperature
photometry
strip
trends
analysis
parameter
trend

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Sullivan, D. J., Metcalfe, T. S., O'Donoghue, D., Winget, D. E., Kilkenny, D., Van Wyk, F., ... Chevreton, M. (2008). Whole Earth Telescope observations of the hot helium atmosphere pulsating white dwarf EC 20058-5234. Monthly Notices of the Royal Astronomical Society, 387(1), 137-152. https://doi.org/10.1111/j.1365-2966.2008.13074.x
Sullivan, D. J. ; Metcalfe, T. S. ; O'Donoghue, D. ; Winget, D. E. ; Kilkenny, D. ; Van Wyk, F. ; Kanaan, A. ; Kepler, S. O. ; Nitta, A. ; Kawaler, S. D. ; Montgomery, M. H. ; Nather, R. E. ; O'Brien, M. S. ; Kim, Agnes ; Wood, M. ; Jiang, X. J. ; Leibowitz, E. M. ; Ibbetson, P. ; Zola, S. ; Krzesinski, J. ; Pajdosz, G. ; Vauclair, G. ; Dolez, N. ; Chevreton, M. / Whole Earth Telescope observations of the hot helium atmosphere pulsating white dwarf EC 20058-5234. In: Monthly Notices of the Royal Astronomical Society. 2008 ; Vol. 387, No. 1. pp. 137-152.
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abstract = "We present the analysis of a total of 177 h of high-quality optical time-series photometry of the helium atmosphere pulsating white dwarf (DBV) EC 20058-5234. The bulk of the observations (135 h) were obtained during a WET campaign (XCOV15) in 1997 July that featured coordinated observing from four southern observatory sites over an 8-d period. The remaining data (42 h) were obtained in 2004 June at Mt John Observatory in NZ over a one-week observing period. This work significantly extends the discovery observations of this low-amplitude (few per cent) pulsator by increasing the number of detected frequencies from 8 to 18, and employs a simulation procedure to confirm the reality of these frequencies to a high level of significance (1 in 1000). The nature of the observed pulsation spectrum precludes identification of unique pulsation mode properties using any clearly discernable trends. However, we have used a global modelling procedure employing genetic algorithm techniques to identify the n, ℓ values of eight pulsation modes, and thereby obtain asteroseismic measurements of several model parameters, including the stellar mass (0.55 M ⊙ ) and T eff (∼28 200 K). These values are consistent with those derived from published spectral fitting: T eff ∼ 28 400 K and log g ∼ 7.86. We also present persuasive evidence from apparent rotational mode splitting for two of the modes that indicates this compact object is a relatively rapid rotator with a period of 2 h. In direct analogy with the corresponding properties of the hydrogen (DAV) atmosphere pulsators, the stable low-amplitude pulsation behaviour of EC 20058 is entirely consistent with its inferred effective temperature, which indicates it is close to the blue edge of the DBV instability strip. Arguably, our most significant result from this work is the clear demonstration that EC 20058 is a very stable pulsator with several dominant pulsation modes that can be monitored for their long-term stability.",
author = "Sullivan, {D. J.} and Metcalfe, {T. S.} and D. O'Donoghue and Winget, {D. E.} and D. Kilkenny and {Van Wyk}, F. and A. Kanaan and Kepler, {S. O.} and A. Nitta and Kawaler, {S. D.} and Montgomery, {M. H.} and Nather, {R. E.} and O'Brien, {M. S.} and Agnes Kim and M. Wood and Jiang, {X. J.} and Leibowitz, {E. M.} and P. Ibbetson and S. Zola and J. Krzesinski and G. Pajdosz and G. Vauclair and N. Dolez and M. Chevreton",
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Sullivan, DJ, Metcalfe, TS, O'Donoghue, D, Winget, DE, Kilkenny, D, Van Wyk, F, Kanaan, A, Kepler, SO, Nitta, A, Kawaler, SD, Montgomery, MH, Nather, RE, O'Brien, MS, Kim, A, Wood, M, Jiang, XJ, Leibowitz, EM, Ibbetson, P, Zola, S, Krzesinski, J, Pajdosz, G, Vauclair, G, Dolez, N & Chevreton, M 2008, 'Whole Earth Telescope observations of the hot helium atmosphere pulsating white dwarf EC 20058-5234', Monthly Notices of the Royal Astronomical Society, vol. 387, no. 1, pp. 137-152. https://doi.org/10.1111/j.1365-2966.2008.13074.x

Whole Earth Telescope observations of the hot helium atmosphere pulsating white dwarf EC 20058-5234. / Sullivan, D. J.; Metcalfe, T. S.; O'Donoghue, D.; Winget, D. E.; Kilkenny, D.; Van Wyk, F.; Kanaan, A.; Kepler, S. O.; Nitta, A.; Kawaler, S. D.; Montgomery, M. H.; Nather, R. E.; O'Brien, M. S.; Kim, Agnes; Wood, M.; Jiang, X. J.; Leibowitz, E. M.; Ibbetson, P.; Zola, S.; Krzesinski, J.; Pajdosz, G.; Vauclair, G.; Dolez, N.; Chevreton, M.

In: Monthly Notices of the Royal Astronomical Society, Vol. 387, No. 1, 01.06.2008, p. 137-152.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Whole Earth Telescope observations of the hot helium atmosphere pulsating white dwarf EC 20058-5234

AU - Sullivan, D. J.

AU - Metcalfe, T. S.

AU - O'Donoghue, D.

AU - Winget, D. E.

AU - Kilkenny, D.

AU - Van Wyk, F.

AU - Kanaan, A.

AU - Kepler, S. O.

AU - Nitta, A.

AU - Kawaler, S. D.

AU - Montgomery, M. H.

AU - Nather, R. E.

AU - O'Brien, M. S.

AU - Kim, Agnes

AU - Wood, M.

AU - Jiang, X. J.

AU - Leibowitz, E. M.

AU - Ibbetson, P.

AU - Zola, S.

AU - Krzesinski, J.

AU - Pajdosz, G.

AU - Vauclair, G.

AU - Dolez, N.

AU - Chevreton, M.

PY - 2008/6/1

Y1 - 2008/6/1

N2 - We present the analysis of a total of 177 h of high-quality optical time-series photometry of the helium atmosphere pulsating white dwarf (DBV) EC 20058-5234. The bulk of the observations (135 h) were obtained during a WET campaign (XCOV15) in 1997 July that featured coordinated observing from four southern observatory sites over an 8-d period. The remaining data (42 h) were obtained in 2004 June at Mt John Observatory in NZ over a one-week observing period. This work significantly extends the discovery observations of this low-amplitude (few per cent) pulsator by increasing the number of detected frequencies from 8 to 18, and employs a simulation procedure to confirm the reality of these frequencies to a high level of significance (1 in 1000). The nature of the observed pulsation spectrum precludes identification of unique pulsation mode properties using any clearly discernable trends. However, we have used a global modelling procedure employing genetic algorithm techniques to identify the n, ℓ values of eight pulsation modes, and thereby obtain asteroseismic measurements of several model parameters, including the stellar mass (0.55 M ⊙ ) and T eff (∼28 200 K). These values are consistent with those derived from published spectral fitting: T eff ∼ 28 400 K and log g ∼ 7.86. We also present persuasive evidence from apparent rotational mode splitting for two of the modes that indicates this compact object is a relatively rapid rotator with a period of 2 h. In direct analogy with the corresponding properties of the hydrogen (DAV) atmosphere pulsators, the stable low-amplitude pulsation behaviour of EC 20058 is entirely consistent with its inferred effective temperature, which indicates it is close to the blue edge of the DBV instability strip. Arguably, our most significant result from this work is the clear demonstration that EC 20058 is a very stable pulsator with several dominant pulsation modes that can be monitored for their long-term stability.

AB - We present the analysis of a total of 177 h of high-quality optical time-series photometry of the helium atmosphere pulsating white dwarf (DBV) EC 20058-5234. The bulk of the observations (135 h) were obtained during a WET campaign (XCOV15) in 1997 July that featured coordinated observing from four southern observatory sites over an 8-d period. The remaining data (42 h) were obtained in 2004 June at Mt John Observatory in NZ over a one-week observing period. This work significantly extends the discovery observations of this low-amplitude (few per cent) pulsator by increasing the number of detected frequencies from 8 to 18, and employs a simulation procedure to confirm the reality of these frequencies to a high level of significance (1 in 1000). The nature of the observed pulsation spectrum precludes identification of unique pulsation mode properties using any clearly discernable trends. However, we have used a global modelling procedure employing genetic algorithm techniques to identify the n, ℓ values of eight pulsation modes, and thereby obtain asteroseismic measurements of several model parameters, including the stellar mass (0.55 M ⊙ ) and T eff (∼28 200 K). These values are consistent with those derived from published spectral fitting: T eff ∼ 28 400 K and log g ∼ 7.86. We also present persuasive evidence from apparent rotational mode splitting for two of the modes that indicates this compact object is a relatively rapid rotator with a period of 2 h. In direct analogy with the corresponding properties of the hydrogen (DAV) atmosphere pulsators, the stable low-amplitude pulsation behaviour of EC 20058 is entirely consistent with its inferred effective temperature, which indicates it is close to the blue edge of the DBV instability strip. Arguably, our most significant result from this work is the clear demonstration that EC 20058 is a very stable pulsator with several dominant pulsation modes that can be monitored for their long-term stability.

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