Whole Earth Telescope observations of the hot helium atmosphere pulsating white dwarf EC 20058−5234
Corresponding Author
D. J. Sullivan
School of Chemical & Physical Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand
E-mail: [email protected]
Visiting astronomer, Mt John University Observatory, operated by the Department of Physics & Astronomy, University of Canterbury.
Search for more papers by this authorT. S. Metcalfe
Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712, USA
High Altitude Observatory, National Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307, USA
Search for more papers by this authorD. O'Donoghue
South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa
Search for more papers by this authorD. E. Winget
Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712, USA
Search for more papers by this authorD. Kilkenny
South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa
Department of Physics, University of the Western Cape, Private Bag X17, Belville 7535, South Africa
Search for more papers by this authorF. Van Wyk
South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa
Search for more papers by this authorA. Kanaan
Departamento de Física, UFSC, CP 476, 88040-900 Florianóplois, SC, Brazil
Search for more papers by this authorS. O. Kepler
Instituto de Física da UFRGS, 91501-900 Porto Alegre, RS, Brazil
Search for more papers by this authorA. Nitta
Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712, USA
Visiting Astronomer, Cerro Tololo Inter-American Observatory, Chile
Gemini Observatory, 670 N A'ohoku Pl., Hilo, HI 96720, USA
Search for more papers by this authorS. D. Kawaler
Department of Physics & Astronomy, Iowa State University, Ames, IA 50011, USA
Search for more papers by this authorM. H. Montgomery
Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712, USA
Search for more papers by this authorR. E. Nather
Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712, USA
Search for more papers by this authorM. S. O'Brien
Department of Physics & Astronomy, Iowa State University, Ames, IA 50011, USA
Department of Astronomy, Yale University, PO Box 208101, New Haven, CT 06511, USA
Search for more papers by this authorA. Bischoff-Kim
Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712, USA
Search for more papers by this authorM. Wood
Department of Physics and Space Sciences and SARA Observatory, Florida Institute of Technology, Melbourne, FL 32901-6975, USA
Search for more papers by this authorX. J. Jiang
Beijing Astronomical Observatory, Chinese Academy of Sciences, 20 Datun Road, Chaoyang, Beijing 100012, China
Search for more papers by this authorE. M. Leibowitz
Department of Physics and Astronomy and Wise Observatory, Tel Aviv University, Tel Aviv 69978, Israel
Search for more papers by this authorP. Ibbetson
Department of Physics and Astronomy and Wise Observatory, Tel Aviv University, Tel Aviv 69978, Israel
Search for more papers by this authorS. Zola
Astronomical Observatory, Jagiellonian University, Ul. Orla 171, 30-244 Cracow, Poland
Mount Suhora Observatory, Pedagogical University, Ul. Podchoraazych 2, 30-024 Cracow, Poland
Search for more papers by this authorJ. Krzesinski
Mount Suhora Observatory, Pedagogical University, Ul. Podchoraazych 2, 30-024 Cracow, Poland
Search for more papers by this authorG. Pajdosz
Mount Suhora Observatory, Pedagogical University, Ul. Podchoraazych 2, 30-024 Cracow, Poland
Search for more papers by this authorG. Vauclair
Observatoire Midi-Pyrénées, Université Paul Sabatier, CNRS/UMR5572, 14 Avenue Edouard Belin, 31400 Toulouse, France
Search for more papers by this authorN. Dolez
Observatoire Midi-Pyrénées, Université Paul Sabatier, CNRS/UMR5572, 14 Avenue Edouard Belin, 31400 Toulouse, France
Search for more papers by this authorM. Chevreton
Observatoire de Paris-Meudon, LESIA, 92195 Meudon, France
Search for more papers by this authorCorresponding Author
D. J. Sullivan
School of Chemical & Physical Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand
E-mail: [email protected]
Visiting astronomer, Mt John University Observatory, operated by the Department of Physics & Astronomy, University of Canterbury.
Search for more papers by this authorT. S. Metcalfe
Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712, USA
High Altitude Observatory, National Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307, USA
Search for more papers by this authorD. O'Donoghue
South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa
Search for more papers by this authorD. E. Winget
Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712, USA
Search for more papers by this authorD. Kilkenny
South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa
Department of Physics, University of the Western Cape, Private Bag X17, Belville 7535, South Africa
Search for more papers by this authorF. Van Wyk
South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa
Search for more papers by this authorA. Kanaan
Departamento de Física, UFSC, CP 476, 88040-900 Florianóplois, SC, Brazil
Search for more papers by this authorS. O. Kepler
Instituto de Física da UFRGS, 91501-900 Porto Alegre, RS, Brazil
Search for more papers by this authorA. Nitta
Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712, USA
Visiting Astronomer, Cerro Tololo Inter-American Observatory, Chile
Gemini Observatory, 670 N A'ohoku Pl., Hilo, HI 96720, USA
Search for more papers by this authorS. D. Kawaler
Department of Physics & Astronomy, Iowa State University, Ames, IA 50011, USA
Search for more papers by this authorM. H. Montgomery
Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712, USA
Search for more papers by this authorR. E. Nather
Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712, USA
Search for more papers by this authorM. S. O'Brien
Department of Physics & Astronomy, Iowa State University, Ames, IA 50011, USA
Department of Astronomy, Yale University, PO Box 208101, New Haven, CT 06511, USA
Search for more papers by this authorA. Bischoff-Kim
Department of Astronomy and McDonald Observatory, University of Texas, Austin, TX 78712, USA
Search for more papers by this authorM. Wood
Department of Physics and Space Sciences and SARA Observatory, Florida Institute of Technology, Melbourne, FL 32901-6975, USA
Search for more papers by this authorX. J. Jiang
Beijing Astronomical Observatory, Chinese Academy of Sciences, 20 Datun Road, Chaoyang, Beijing 100012, China
Search for more papers by this authorE. M. Leibowitz
Department of Physics and Astronomy and Wise Observatory, Tel Aviv University, Tel Aviv 69978, Israel
Search for more papers by this authorP. Ibbetson
Department of Physics and Astronomy and Wise Observatory, Tel Aviv University, Tel Aviv 69978, Israel
Search for more papers by this authorS. Zola
Astronomical Observatory, Jagiellonian University, Ul. Orla 171, 30-244 Cracow, Poland
Mount Suhora Observatory, Pedagogical University, Ul. Podchoraazych 2, 30-024 Cracow, Poland
Search for more papers by this authorJ. Krzesinski
Mount Suhora Observatory, Pedagogical University, Ul. Podchoraazych 2, 30-024 Cracow, Poland
Search for more papers by this authorG. Pajdosz
Mount Suhora Observatory, Pedagogical University, Ul. Podchoraazych 2, 30-024 Cracow, Poland
Search for more papers by this authorG. Vauclair
Observatoire Midi-Pyrénées, Université Paul Sabatier, CNRS/UMR5572, 14 Avenue Edouard Belin, 31400 Toulouse, France
Search for more papers by this authorN. Dolez
Observatoire Midi-Pyrénées, Université Paul Sabatier, CNRS/UMR5572, 14 Avenue Edouard Belin, 31400 Toulouse, France
Search for more papers by this authorM. Chevreton
Observatoire de Paris-Meudon, LESIA, 92195 Meudon, France
Search for more papers by this authorABSTRACT
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 Teff (∼28 200 K). These values are consistent with those derived from published spectral fitting: Teff∼ 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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