Whole Earth Telescope observations of the subdwarf B star KPD 1930+2752: a rich, short-period pulsator in a close binary
M. D. Reed
(1)
,
S. L. Harms
(1)
,
S. Poindexter
(1)
,
A.-Y. Zhou
(1)
,
J. R. Eggen
(1)
,
M. A. Morris
(1)
,
A. C. Quint
(1)
,
S. Mcdaniel
(1)
,
A. Baran
(2)
,
N. Dolez
(3)
,
Steven D. Kawaler
(4)
,
Donald W. Kurtz
(5)
,
P. A. Moskalik
(6)
,
R. Riddle
(4)
,
S. Zola
(2)
,
R. H. Østensen
(7)
,
J.-E. Solheim
(8)
,
S. O. Kepler
(9)
,
A. F. M. Costa
(10)
,
J. L. Provençal
(11)
,
Fergal Mullally
(12)
,
D. W. Winget
(12)
,
Maja Vuckovic
(4)
,
R. Crowe
(13)
,
D. Terry
(13)
,
R. Avila
(13)
,
B. Berkey
(13)
,
S. Stewart
(13)
,
J. Bodnarik
(13)
,
D. Bolton
(13)
,
P.-M. Binder
(13)
,
Kazuhiro Sekiguchi
(14)
,
D. J. Sullivan
(15)
,
S.-L. Kim
(16)
,
Wen-Ping Chen
(17)
,
C.-W. Chen
(17)
,
H.-C. Lin
(17)
,
X.-J. Jian
(18)
,
H. Wu
(18)
,
J.-P. Gou
(18)
,
Z. Liu
(18)
,
E. M. Leibowitz
(19)
,
Y. Lipkin
(19)
,
M. C. Akan
(20)
,
Ö. Çakirli
(20)
,
R. Janulis
(21)
,
R. Pretorius
(22)
,
W. Ogloza
(2)
,
G. Stachowski
(2)
,
M. Paparó
(23)
,
Robert Szabó
(23)
,
Z. Csubry
(23)
,
D. Zsuffa
(23)
,
R. Silvotti
(24)
,
S. Marinoni
(25)
,
I. Bruni
(26)
,
Gérard Vauclair
(3)
,
Michel Chevreton
(27, 28)
,
Jaymie M. Matthews
(29)
,
A. C. Cameron
(29)
,
Herbert Pablo
(4)
1
Department of Physics, Astronomy, and Materials Science, Missouri State University
2 Mount Suhora Observatory, Cracow Pedagogical University
3 LATT - Laboratoire Astrophysique de Toulouse-Tarbes
4 ISU - Iowa State University
5 Centre for Astrophysics, University of Central Lancashire
6 CAMK - Centrum Astronomiczne im. M. Kopernika, Warszawa
7 Isaac Newton Group of Telescopes
8 UiO - University of Oslo
9 Instituto de Física, Universidade Federal do Rio Grande do Sul
10 Universidade do Estado de Santa Catarina, CAV
11 Mount Cuba Observatory, University of Delaware
12 Department of Astronomy, University of Texas
13 Department of Physics and Astronomy, University of Hawaii
14 NAOJ - National Astronomical Observatory of Japan
15 School of Chemical and Physical Sciences, Victoria University
16 Korea Astronomy Observatory
17 Graduate Institute of Astronomy
18 National Astronomical Observatoires-CAS
19 TAU - Tel Aviv University
20 Ege University Observatory
21 Vilnius University [Vilnius]
22 SAAO - South African Astronomical Observatory
23 Konkoly Observatory, Research Center for Astronomy and Earth Sciences
24 OATo - INAF - Osservatorio Astrofisico di Torino
25 UNIBO - Alma Mater Studiorum Università di Bologna = University of Bologna
26 OABO - INAF-Osservatorio Astronomico di Bologna
27 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
28 Etoile
29 UBC - University of British Columbia [Canada]
2 Mount Suhora Observatory, Cracow Pedagogical University
3 LATT - Laboratoire Astrophysique de Toulouse-Tarbes
4 ISU - Iowa State University
5 Centre for Astrophysics, University of Central Lancashire
6 CAMK - Centrum Astronomiczne im. M. Kopernika, Warszawa
7 Isaac Newton Group of Telescopes
8 UiO - University of Oslo
9 Instituto de Física, Universidade Federal do Rio Grande do Sul
10 Universidade do Estado de Santa Catarina, CAV
11 Mount Cuba Observatory, University of Delaware
12 Department of Astronomy, University of Texas
13 Department of Physics and Astronomy, University of Hawaii
14 NAOJ - National Astronomical Observatory of Japan
15 School of Chemical and Physical Sciences, Victoria University
16 Korea Astronomy Observatory
17 Graduate Institute of Astronomy
18 National Astronomical Observatoires-CAS
19 TAU - Tel Aviv University
20 Ege University Observatory
21 Vilnius University [Vilnius]
22 SAAO - South African Astronomical Observatory
23 Konkoly Observatory, Research Center for Astronomy and Earth Sciences
24 OATo - INAF - Osservatorio Astrofisico di Torino
25 UNIBO - Alma Mater Studiorum Università di Bologna = University of Bologna
26 OABO - INAF-Osservatorio Astronomico di Bologna
27 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
28 Etoile
29 UBC - University of British Columbia [Canada]
Résumé
KPD 1930+2752 is a short-period pulsating subdwarf B (sdB) star. It is also an ellipsoidal variable with a known binary period of 2.3 h. The companion is most likely a white dwarf and the total mass of the system is close to the Chandresekhar limit. In this paper, we report the results of Whole Earth Telescope (WET) photometric observations during 2003 and a smaller multisite campaign of 2002. From 355 h of WET data, we detect 68 pulsation frequencies and suggest an additional 13 frequencies within a crowded and complex temporal spectrum between 3065 and 6343 muHz (periods between 326 and 157 s). We examine pulsation properties including phase and amplitude stability in an attempt to understand the nature of the pulsation mechanism. We examine a stochastic mechanism by comparing amplitude variations with simulated stochastic data. We also use the binary nature of KPD 1930+2752 for identifying pulsation modes via multiplet structure and a tidally induced pulsation geometry. Our results indicate a complicated pulsation structure that includes short-period (≈16 h) amplitude variability, rotationally split modes, tidally induced modes and some pulsations which are geometrically limited on the sdB star.