A binary signature in the non-thermal radio-emitter Cyg OB2 #9

Abstract

Aims: Non-thermal radio emission associated with massive stars is believed to arise from a wind-wind collision in a binary system. However, the evidence of binarity is still lacking in some cases, notably Cyg OB2 #9 Methods: For several years, we have been monitoring this heavily-reddened star from various observatories. This campaign allowed us to probe variations both on short and long timescales and constitutes the first in-depth study of the visible spectrum of this object. Results: Our observations provide the very first direct evidence of a companion in Cyg OB2 #9, confirming the theoretical wind-wind collision scenario. These data suggest a highly eccentric orbit with a period of a few years, compatible with the 2yr-timescale measured in the radio range. In addition, the signature of the wind-wind collision is very likely reflected in the behaviour of some emission lines.

accepted by A&A, 4 p, 3figures

References in corpus (4)

• Radio, X-ray, and gamma-ray Emission Models of the Colliding Winds Binary WR 140
• A Radial Velocity Survey of the Cygnus OB2 Association
• Non-thermal emission processes in massive binaries
• Non-thermal radio emission from O-type stars III. Is Cyg OB2 No. 9 a wind-colliding binary?

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• A spectroscopic investigation of the O-type star population in four Cygnus OB associations. I. Determination of the binary fraction
• A multiwavelength investigation of the massive eclipsing binary Cyg OB2 #5
• Non-thermal radio emission from O-type stars. IV. Cyg OB2 No. 8A
• Additional Massive Binaries in the Cygnus OB2 Association
• The 2.35 year itch of Cyg OB2 #9 - I. Optical and X-ray monitoring
• Five More Massive Binaries in the Cygnus OB2 Association
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• The eclipsing, double-lined, Of supergiant binary Cyg OB2-B17
• The 2.35 year itch of Cyg OB2 #9. II. Radio monitoring
• A test for the theory of colliding winds: the periastron passage of 9 Sagittarii I. X-ray and optical spectroscopy
• First orbital solution for the non-thermal emitter Cyg OB2 #9
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• Resolving the dynamical mass tension of the massive binary 9 Sagittarii
• The 2.35 year itch of Cygnus OB2#9 III. X-ray and radio emission analysis based on three dimensional hydrodynamical modelling
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• An R- and I-Band Photometric Variability Survey of the Cygnus OB2 Association
• The colliding-wind binary HD 168112