Sódor, Á. ; De Cat, P. ; Wright, D. J. ; Neiner, C. ; Briquet, M. ; Dukes, R. J. ; Fekel, F. C. ; Henry, G. W. ; Williamson, M. H. ; Muterspaugh, M. W. ; Brunsden, E. ; Pollard, K. R. ; Cottrell, P. L. ; Maisonneuve, F. ; Kilmartin, P. M. ; Matthews, J. M. ; Kallinger, T. ; Beck, P. G. ; Kambe, E. ; Engelbrecht, C. A. ; Czanik, R. J. ; Yang, S. ; Hashimoto, O. ; Honda, S. ; Fu, J.-N. ; Castanheira, B. ; Lehmann, H. ; Behara, N. ; Van Winckel, H. ; Scaringi, S. ; Menu, J. ; Lobel, A. ; Lampens, P. ; Mathias, P.

published in Precision Asteroseismology, 301, pp. 491-492 (2014)

Abstract: 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.

DOI: 10.1017/S1743921313015202
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