van Loo, S. ; Blomme, R. ; Dougherty, S. M. ; Runacres, M. C.

published in Astronomy and Astrophysics, 483, pp. 585-590 (2008)

Abstract: The star Cyg OB2 No. 9 is a well-known non-thermal radio emitter. Recent theoretical work suggests that all such O-stars should be in a binary or a multiple system. However, there is no spectroscopic evidence of a binary component. Re-analysis of radio observations from the VLA of this system over 25 years has revealed that the non-thermal emission varies with a period of 2.35±0.02 yr. This is interpreted as a strong suggestion of a binary system, with the non-thermal emission arising in a wind-collision region. We derived some preliminary orbital parameters for this putative binary and revised the mass-loss rate of the primary star downward from previous estimates. Appendix A is only available in electronic form at http://www.aanda.org

DOI: 10.1051/0004-6361:200809367
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