posted on 2006-12-27, 13:25authored byA. Kanaan, A. Nitta, D.E. Winget, S.O. Kepler, M.H. Montgomery, T.S. Metcalfe, H. Oliveira, L. Fraga, A.F.M. da Costa, J.E.S. Costa, B.G. Castanheira, O. Giovannini, R.E. Nather, A. Mukudam, S. Kawaler, M.S. O'Brien, M.D. Reed, S.J. Kleinman, J.L. Provencal, T.K. Watson, D. Kilkenny, D.J. Sullivan, T. Sullivan, B. Shobbrook, X.J. Jiang, B.N. Ashoka, S. Seetha, E. Leibowitz, P. Ibbetson, H. Mendelson, E.G. Meištas, R. Kalytis, D. Ališauskas, D. O'Donoghue, D. Buckley, P. Martinez, F. van Wyk, R. Stobie, F. Marang, L. van Zyl, W. Ogloza, J. Krzesinski, S. Zola, P. Moskalik, M. Breger, A. Stankov, R. Silvotti, A. Piccioni, G. Vauclair, N. Dolez, M. Chevreton, J. Deetjen, S. Dreizler, S. Schuh, J.M. Gonzalez Perez, R. Østensen, A. Ulla, M. Manteiga, O. Suarez, Matthew R. Burleigh, Martin A. Barstow
BPM 37093 is the only hydrogen-atmosphere white dwarf currently known which has sufficient mass (~1.1 MO) to theoretically crystallize while still inside the ZZ Ceti instability strip (Teff ~ 12 000 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.
History
Citation
Astronomy and Astrophysics, 2005, 432, pp.219-224
Published in
Astronomy and Astrophysics
Publisher
EDP Sciences
Available date
2006-12-27
Notes
The definitive version of this paper is available from www.aanda.org