Whole Earth Telescope observations of BPM 37093 : a seismological test of crystallization theory in white dwarfs

BPM 37093 is the only hydrogen-atmosphere white dwarf currently known which has sufficient mass (~1.1 Mʘ) 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 direc...

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Detalles Bibliográficos
Autores: Kanaan Neto, Antonio Nemer, Nitta, Atsuko, Winget, Donald Earl, Kepler, Souza Oliveira, Montgomery, Michael Houston, Metcalfe, Travis S., Oliveira, H., Fraga, Luciano, Costa, Alex Fabiano Murillo da, Costa, Jose Eduardo da Silveira, Castanheira, Bárbara Garcia, Giovannini Junior, Odilon, Nather, R. Edward, Mukadam, Anjum Shagufta, Kawaler, Steven D., O'Brien, M. Sean, Reed, M. D., Kleinman, Scot James, Provencal, Judith L., Watson, Todd K., Kilkenny, Dave, Sullivan, Denis J., Sullivan, Terry, Shobbrook, Bob, Jiang, Xiaojun, Ashoka, B.N., Seetha, S., Leibowitz, Elia M., Ibbetson, Peter A., Mendelson, Haim, Meistas, Edmundas G., Kalytis, Romualdas, Alisauskas, Darius, O'Donoghue, Darragh, Buckley, David A.H., Martinez, Peter, Van Wyk, Francois, Stobie, Robert S., Marang, Fred, Van Zyl, L., Ogloza, Waldemar, Krzesinski, Jerzy, Zola, Staszek, Moskalik, Pawel, Breger, M., Stankov, A., Silvotti, Roberto, Piccioni, Adalberto, Vauclair, Gérard, Dolez, Noël, Chevreton, Michel, Deetjen, Jochen L., Dreizler, Stefan, Schuh, Sonja L., Gonzalez Perez, Jose Miguel, Ostensen, Roy, Ulla, Ana, Manteiga, Minia, Suarez, Olga, Burleigh, Matt, Barstow, Martin A.
Tipo de recurso: artículo
Estado:Versión publicada
Fecha de publicación:2005
País:Brasil
Institución:Universidade Federal do Rio Grande do Sul (UFRGS)
Repositorio:Repositório Institucional da UFRGS
Idioma:inglés
OAI Identifier:oai:www.lume.ufrgs.br:10183/98773
Acceso en línea:http://hdl.handle.net/10183/98773
Access Level:acceso abierto
Palabra clave:Anãs brancas
Evolucao estelar
Estrelas variaveis
Interior estelar
Hidrogênio
Massa estelar
Pulsacoes estelares
Stars: evolution
Stars: individual: BPM 37093
Stars: interiors
Stars: oscillations
White dwarfs
Descripción
Sumario:BPM 37093 is the only hydrogen-atmosphere white dwarf currently known which has sufficient mass (~1.1 Mʘ) 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.

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