Á. Sódor, Royal Observatory of BelgiumFollow
Peter De Cat, Royal Observatory of Belgium
David J. Wright, Royal Observatory of Belgium
Coralie Neiner, LESIA, Observatoire de ParisFollow
Maryline Briquet, Université de Liège
Patricia Lampens, Royal Observatory of Belgium
Robert J. Dukes, College of Charleston
Gregory W. Henry, Tennessee State UniversityFollow
Michael H. Williamson, Tennessee State UniversityFollow
Emily Brunsden, University of Canterbury
Karen R. Pollard, University of Canterbury
Peter L. Cottrell, University of Canterbury
Florian Maisonneuve, University of Canterbury
Pam M. Kilmartin, University of Canterbury
Jaymie Matthews, University of British ColumbiaFollow
Thomas Kallinger, University of Vienna
Paul G. Beck, Katholieke Universiteit Leuven
Eiji Kambe, Okayama Astrophysical Observatory
Chris A. Engelbrecht, University of Johannesburg
Robert J. Czanik, North-West University (South Africa)
Stephenson Yang, University of Victoria
Osamu Hashimoto, Gunma Astronomical Observatory
Satoshi Honda, Gunma Astronomical Observatory
Jian-Ning Fu, Beijing Normal University
Barbara Castanheira, University of Texas at Austin
Holger Lehmann, Thüringer Landessternwarte Tautenburg
Zsófia Bognár, Hungarian Academy of Sciences
Natalie Behara, Université Libre de Bruxelles
Simone Scaringi, Katholieke Universiteit Leuven
Hans Van Winckel, Katholieke Universiteit Leuven
Jonathan Menu, Katholieke Universiteit Leuven
Alex Lobel, Royal Observatory of BelgiumFollow
P. Mathias, Université de Toulouse
Sophie Saesen, Katholieke Universiteit Leuven
Maja Vučković, Katholieke Universiteit Leuven
The MiMeS Collaboration

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We carried out an extensive observational study of the Slowly Pulsating B (SPB) star, HD 25558. The ≈2000 spectra obtained at different observatories, the ground-based and MOST satellite light curves revealed that this object is a double-lined spectroscopic binary with an orbital period of about nine years. The observations do not allow the inference of an orbital solution. We determined the physical parameters of the components, and found that both lie within the SPB instability strip. Accordingly, both show line-profile variations due to stellar pulsations. 11 independent frequencies were identified in the data. All the frequencies were attributed to one of the two components based on pixel-by-pixel variability analysis of the line profiles. Spectroscopic and photometric mode identification was also performed for the frequencies of both stars. These results suggest that the inclination and rotation of the two components are rather different. The primary is a slow rotator with ≈6 d period, seen at ≈60° inclination, while the secondary rotates fast with ≈1.2 d period, and is seen at ≈20° inclination. Spectropolarimetric measurements revealed that the secondary component has a magnetic field with at least a few hundred Gauss strength, while no magnetic field can be detected in the primary.