[en] 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.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Sódor, Á.; Royal Observatory of Belgium, Brussel, Belgium
De Cat, P.; Royal Observatory of Belgium, Brussel, Belgium
Wright, D. J.; Royal Observatory of Belgium, Brussel, Belgium
Neiner, C.; LESIA, CNRS, Observatoire de Paris, UMPC, Université Paris Diderot, Meudon, France
Briquet, Maryline ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Dukes, R. J.; Department of Physics and Astronomy, The College of Charleston, Charleston, SC, USA
Fekel, F. C.; Center of Excellence in Information Systems, Tennessee State University, Nashville, TN, USA
Henry, G. W.; Center of Excellence in Information Systems, Tennessee State University, Nashville, TN, USA
Williamson, M. H.; Center of Excellence in Information Systems, Tennessee State University, Nashville, TN, USA
Muterspaugh, M. W.; Center of Excellence in Information Systems, Tennessee State University, Nashville, TN, USA
Brunsden, E.; Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand
Pollard, K. R.; Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand
Cottrell, P. L.; Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand
Maisonneuve, F.; Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand
Kilmartin, P. M.; Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand
Matthews, J. M.; Dept. of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada
Kallinger, T.; Institute for Astronomy, University of Vienna, Vienna, Austria
Beck, P. G.; Instituut voor Sterrenkunde, K. U. Leuven, Leuven, Belgium
Kambe, E.; Okayama Astrophysical Observatory, National Astronomical Observatory, Okayama, Japan
Engelbrecht, C. A.; Department of Physics, University of Johannesburg, Johannesburg, South Africa
Czanik, R. J.; Dept. of Phys., Potchefstroom Campus, North-West University, Potchefstroom, South Africa
Yang, S.; Department of Physics and Astronomy, University of Victoria, Victoria, BC, Canada
Hashimoto, O.; Gunma Astronomical Observatory, Takayama-mura, Agatsuma, Gunma, Japan
Honda, S.; Gunma Astronomical Observatory, Takayama-mura, Agatsuma, Gunma, Japan
Fu, J.-N.; Department of Astronomy, Beijing Normal University, Beijing, China
Castanheira, B.; Department of Astronomy, The University of Texas at Austin, Austin, TX, USA
