Whole Earth Telescope observations of BPM 37093: A seismological test of crystallization theory in white dwarfs
A. Kanaan
(1)
,
A. Nitta
(2)
,
D. E. Winget
(3)
,
S. O. Kepler
(4)
,
M. H. Montgomery
(5)
,
Travis S. Metcalfe
(6)
,
H. Oliveira
(1)
,
L. Fraga
(1)
,
A. F. M. da Costa
(4)
,
José Eduardo Costa
(4)
,
B. G. Castanheira
(4)
,
O. Giovannini
(7)
,
R. E. Nather
(3)
,
A. Mukadam
(3)
,
Steven D. Kawaler
(8)
,
M. S. O'Brien
(8)
,
M. D. Reed
(8)
,
S. J. Kleinman
(2)
,
J. L. Provençal
(9)
,
T. K. Watson
(10)
,
D. M. Kilkenny
(11)
,
D. J. Sullivan
(12)
,
T. Sullivan
(12)
,
B. Shobbrook
(13)
,
X. J. Jiang
(14)
,
B. N. Ashoka
(15)
,
S. Seetha
(15)
,
E. M. Leibowitz
(16)
,
P. Ibbetson
(16)
,
H. Mendelson
(16)
,
E. G. Meistas
(17)
,
R. Kalytis
(17)
,
D. Alisauskas
(17)
,
Darragh O'Donoghue
(11)
,
D. Buckley
(11)
,
Patrice Martinez
(11)
,
F. van Wyk
(11)
,
R. S. Stobie
(11)
,
F. Marang
(11)
,
L. van Zyl
(11)
,
W. Ogloza
(18)
,
J. Krzesinski
(18)
,
S. Zola
(18)
,
P. A. Moskalik
(19)
,
M. Breger
(20)
,
Anamarija Stankov
(20)
,
R. Silvotti
(21)
,
A. Piccioni
(22)
,
Gérard Vauclair
(23)
,
N. Dolez
(23)
,
Michel Chevreton
(24, 25, 26)
,
J. Deetjen
(27)
,
Stefan Dreizler
(27)
,
S. Schuh
(27)
,
J. M. Gonzalez Perez
(28)
,
R. Østensen
(29)
,
A. Ulla
(30)
,
M. Manteiga
(30)
,
O. Suarez
(30)
,
M. R. Burleigh
(31)
,
Martin A. Barstow
(31)
1
Departamento de Física (CFM), Universidade Federal de Santa Catarina
2 Apache Point Observatory
3 Department of Astronomy, University of Texas
4 Instituto de Física, Universidade Federal do Rio Grande do Sul
5 IoA - Institute of Astronomy, University of Cambridge
6 CfA - Harvard-Smithsonian Center for Astrophysics
7 Departamento de Física e Química, Universidade de Caxias do Sul
8 ISU - Iowa State University
9 Department of Physics and Astronomy, University of Delaware
10 Southwestern University
11 SAAO - South African Astronomical Observatory
12 Victoria University of Wellington
13 The University of Sydney
14 Astronomical Observatory, Academy of Sciences
15 Indian Space Research Organization
16 TAU - Tel Aviv University
17 Vilnius University [Vilnius]
18 Mount Suhora Observatory, Cracow Pedagogical University
19 CAMK - Centrum Astronomiczne im. M. Kopernika, Warszawa
20 IfA - Institut für Astronomie, Universität Wien
21 INAF-OAC - INAF-Osservatorio Astronomico di Capodimonte
22 UNIBO - Alma Mater Studiorum Università di Bologna = University of Bologna
23 OMP - Observatoire Midi-Pyrénées
24 Observatoire de Paris
25 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
26 Pôle Astronomie du LESIA
27 Eberhard Karls Universität Tübingen = University of Tübingen
28 University of Tromsø
29 Isaac Newton Group of Telescopes
30 Universidade de Vigo
31 University of Leicester
2 Apache Point Observatory
3 Department of Astronomy, University of Texas
4 Instituto de Física, Universidade Federal do Rio Grande do Sul
5 IoA - Institute of Astronomy, University of Cambridge
6 CfA - Harvard-Smithsonian Center for Astrophysics
7 Departamento de Física e Química, Universidade de Caxias do Sul
8 ISU - Iowa State University
9 Department of Physics and Astronomy, University of Delaware
10 Southwestern University
11 SAAO - South African Astronomical Observatory
12 Victoria University of Wellington
13 The University of Sydney
14 Astronomical Observatory, Academy of Sciences
15 Indian Space Research Organization
16 TAU - Tel Aviv University
17 Vilnius University [Vilnius]
18 Mount Suhora Observatory, Cracow Pedagogical University
19 CAMK - Centrum Astronomiczne im. M. Kopernika, Warszawa
20 IfA - Institut für Astronomie, Universität Wien
21 INAF-OAC - INAF-Osservatorio Astronomico di Capodimonte
22 UNIBO - Alma Mater Studiorum Università di Bologna = University of Bologna
23 OMP - Observatoire Midi-Pyrénées
24 Observatoire de Paris
25 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
26 Pôle Astronomie du LESIA
27 Eberhard Karls Universität Tübingen = University of Tübingen
28 University of Tromsø
29 Isaac Newton Group of Telescopes
30 Universidade de Vigo
31 University of Leicester
Résumé
BPM 37093 is the only hydrogen-atmosphere white dwarf currently known which has sufficient mass (~1.1 M&sun;) 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.
Domaines
Astrophysique [astro-ph]Origine | Fichiers éditeurs autorisés sur une archive ouverte |
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