Issue |
A&A
Volume 432, Number 1, March II 2005
|
|
---|---|---|
Page(s) | 219 - 224 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20041125 | |
Published online | 22 February 2005 |
Whole Earth Telescope observations of BPM 37093: A seismological test of crystallization theory in white dwarfs*
1
Departamento de Física Universidade Federal de Santa Catarina, CP 476, 88040-900 Florianópolis, SC, Brazil e-mail: kanaan@astro.ufsc.br
2
Apache Point Observatory, 2001 Apache Point Road, PO Box 59, Sunspot, NM 88349, USA
3
Department of Astronomy, 1 University Station Stop C1400, University of Texas, Austin, TX 78712, USA
4
Instituto de Física, Universidade Federal de Rio Grande do Sul, CP 10501, 91501-970 Porto Alegre, RS, Brazil
5
Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
6
Harvard-Smithsonian Center for Astrophysics, USA
7
Departamento de Fisica e Quimica, UCS, Brazil
8
Dept. of Physics & Astronomy, Iowa State University, USA
9
Astronomy Dept., Southwest Missouri State University, USA
10
Dept. of Physics & Astronomy, University of Delaware, USA
11
Southwestern University, Georgetown, TX, USA
12
South African Astronomical Observatory, South Africa
13
Victoria University of Wellington, New Zealand
14
Chatterton Astronomy Dept., University of Sydney, Australia
15
Astronomical Observatory, Academy of Sciences, PR China
16
Indian Space Research Organization, India
17
Wise Observatory, Tel-Aviv University, Israel
18
Institute of Theoretical Physics & Astronomy, Lithuania
19
Vilnius University, Lithuania
20
Mt. Suhora Observatory, Cracow Pedagogical University, Poland
21
Astronomical Observatory, Jagiellonia University, Poland
22
Copernicus Astronomical Center, Poland
23
Institut für Astronomie, Universität Wien, Austria
24
INAF – Osservatorio Astronomico di Capodimonte, Italy
25
Dipartimento di Astronomia, Università di Bologna, Italy
26
Université Paul Sabatier, Observatoire Midi-Pyrénées, France
27
Observatoire de Paris-Meudon, France
28
Institut für Astronomie und Astrophysik, Germany
29
Universitätssternwarte Göttingen, Germany
30
University of Tromsø, Norway
31
Isaac Newton Group, Spain
32
Departamento de Física Aplicada, Universidad de Vigo, Spain
33
Dept. of Physics & Astronomy, University of Leicester, UK
Received:
20
April
2004
Accepted:
31
October
2004
BPM 37093 is the only hydrogen-atmosphere white dwarf currently
known which has sufficient mass (~1.1 ) to theoretically
crystallize while still inside the ZZ Ceti instability strip (
K). As a consequence, this star represents our first
opportunity to test crystallization theory directly. If the core is
substantially crystallized, then the inner boundary for each pulsation
mode will be located at the top of the solid core rather than at the
center of the star, affecting mainly the average period spacing. This is
distinct from the “mode trapping” caused by the stratified surface
layers, which modifies the pulsation periods more selectively. In this
paper we report on Whole Earth Telescope observations of BPM 37093
obtained in 1998 and 1999. Based on a simple analysis of the average
period spacing we conclude that a large fraction of the total stellar mass
is likely to be crystallized.
Key words: stars: evolution / stars: individual: BPM 37093 / stars: interiors / stars: oscillations / white dwarfs
Based on observations obtained at: Observatório do Pico dos Dias (OPD) Brazil, the European Southern Observatory (ESO) Chile, South African Astronomical Observatory (SAAO), Mt. John University Observatory (MJUO) New Zealand, Siding Spring Observatory (SSO) Australia, and Cerro Tololo Inter-American Observatory (CTIO), a division of the National Optical Astronomy Observatories, which is operated by the Association of Universities for Research in Astronomy, Inc. under cooperative agreement with the National Science Foundation.
© ESO, 2005
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