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Extensive spectroscopic and photometric study of HD 25558, a long orbital-period binary with two SPB components

Published online by Cambridge University Press:  18 February 2014

Á. Sódor ,
P. De Cat ,
D. J. Wright ,
C. Neiner ,
M. Briquet ,
R. J. Dukes ,
F. C. Fekel ,
G. W. Henry ,
M. H. Williamson  and
M. W. Muterspaugh
...Show all authors
Á. Sódor
Affiliation:
Royal Observatory of Belgium, Brussel, Belgium Konkoly Observatory, Hungarian Academy of Sciences, Budapest, Hungary
P. De Cat
Affiliation:
Royal Observatory of Belgium, Brussel, Belgium
D. J. Wright
Affiliation:
Royal Observatory of Belgium, Brussel, Belgium School of Physics, University of New South Wales, Sydney, Australia
C. Neiner
Affiliation:
LESIA, CNRS, Observatoire de Paris, UMPC, Université Paris Diderot, Meudon, France
M. Briquet
Affiliation:
Institut d'Astrophysique et de Géophysique, Université de Liège, Liège, Belgium
R. J. Dukes
Affiliation:
Department of Physics and Astronomy, The College of Charleston, Charleston, SC, USA
F. C. Fekel
Affiliation:
Center of Excellence in Information Systems, Tennessee State University, Nashville, TN, USA
G. W. Henry
Affiliation:
Center of Excellence in Information Systems, Tennessee State University, Nashville, TN, USA
M. H. Williamson
Affiliation:
Center of Excellence in Information Systems, Tennessee State University, Nashville, TN, USA
M. W. Muterspaugh
Affiliation:
Center of Excellence in Information Systems, Tennessee State University, Nashville, TN, USA
E. Brunsden
Affiliation:
Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand
K. R. Pollard
Affiliation:
Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand
P. L. Cottrell
Affiliation:
Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand
F. Maisonneuve
Affiliation:
Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand
P. M. Kilmartin
Affiliation:
Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand
J. M. Matthews
Affiliation:
Dept. of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada
T. Kallinger
Affiliation:
Institute for Astronomy, University of Vienna, Vienna, Austria
P. G. Beck
Affiliation:
Instituut voor Sterrenkunde, K. U. Leuven, Leuven, Belgium
E. Kambe
Affiliation:
Okayama Astrophysical Observatory, National Astronomical Observatory, Okayama, Japan
C. A. Engelbrecht
Affiliation:
Department of Physics, University of Johannesburg, Johannesburg, South Africa
R. J. Czanik
Affiliation:
Dept. of Phys., Potchefstroom Campus, North-West University, Potchefstroom, South Africa
S. Yang
Affiliation:
Department of Physics and Astronomy, University of Victoria, Victoria, BC, Canada
O. Hashimoto
Affiliation:
Gunma Astronomical Observatory, Takayama-mura, Agatsuma, Gunma, Japan
S. Honda
Affiliation:
Gunma Astronomical Observatory, Takayama-mura, Agatsuma, Gunma, Japan Kwasan Observatory, Kyoto University, Kyoto, Japan
J.-N. Fu
Affiliation:
Department of Astronomy, Beijing Normal University, Beijing, China
B. Castanheira
Affiliation:
Department of Astronomy, The University of Texas at Austin, Austin, TX, USA
H. Lehmann
Affiliation:
Thüringer Landessternwarte Tautenburg, Tautenburg, Germany
N. Behara
Affiliation:
Université Libre de Bruxelles, Bruxelles, Belgium
H. Van Winckel
Affiliation:
Instituut voor Sterrenkunde, K. U. Leuven, Leuven, Belgium
S. Scaringi
Affiliation:
Instituut voor Sterrenkunde, K. U. Leuven, Leuven, Belgium
J. Menu
Affiliation:
Instituut voor Sterrenkunde, K. U. Leuven, Leuven, Belgium
A. Lobel
Affiliation:
Royal Observatory of Belgium, Brussel, Belgium
P. Lampens
Affiliation:
Royal Observatory of Belgium, Brussel, Belgium
P. Mathias
Affiliation:
Université de Toulouse, UPS-OMP, IRAP, CNRS, Toulouse, France
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Abstract

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We carried out an extensive photometric and spectroscopic investigation of the SPB binary, HD 25558 (see Fig. 1 for the time and geographic distribution of the observations). The ~2000 spectra obtained at 13 observatories during 5 observing seasons, the ground-based multi-colour light curves and the photometric data from the MOST satellite revealed that this object is a double-lined spectroscopic binary with a very long orbital period of about 9 years. We determined the physical parameters of the components, and have found that both lie within the SPB instability strip. Accordingly, both components show line-profile variations consistent with stellar pulsations. Altogether, 11 independent frequencies and one harmonic frequency were identified in the data. The observational data do not allow the inference of a reliable orbital solution, thus, disentangling cannot be performed on the spectra. Since the lines of the two components are never completely separated, the analysis is very complicated. Nevertheless, pixel-by-pixel variability analysis of the cross-correlated line profiles was successful, and we were able to attribute all the frequencies to the primary or secondary component. Spectroscopic and photometric mode-identification was also performed for several of these frequencies of both binary components. The spectroscopic mode-identification results suggest that the inclination and rotation of the two components are rather different. While the primary is a slow rotator with ~6 d rotation period, seen at ~60° inclination, the secondary rotates fast with ~1.2 d rotation period, and is seen at ~20° inclination. Our spectropolarimetric measurements revealed that the secondary component has a magnetic field with at least a few hundred Gauss strength, while no magnetic field was detected in the primary.

The detailed analysis and results of this study will be published elsewhere.

Keywords

line: profilesstars: binaries: generalstars: oscillations (including pulsations)stars: rotationstars: variables: other

Information

Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 9 , Symposium S301: Precision Asteroseismology , August 2013 , pp. 491 - 492
Copyright
Copyright © International Astronomical Union 2014