The Non-thermal, Time-variable Radio Emission from Cyg OB2 #5: A Wind-collision Region
Abstract
The radio emission from the well-studied massive stellar system Cyg OB2 #5 is known to fluctuate with a period of 6.7 years between a low-flux state, when the emission is entirely of free-free origin, and a high-flux state, when an additional non-thermal component (of hitherto unknown nature) appears. In this paper, we demonstrate that the radio flux of that non-thermal component is steady on timescales of hours and that its morphology is arc-like. This shows that the non-thermal emission results from the collision between the strong wind driven by the known contact binary in the system and that of an unseen companion on a somewhat eccentric orbit with a 6.7 year period and a 5-10 mas semimajor axis. Together with the previously reported wind-collision region located about 0farcs8 to the northeast of the contact binary, so far Cyg OB2 #5 appears to be the only multiple system known to harbor two radio-imaged wind-collision regions.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 2011
- DOI:
- 10.1088/0004-637X/737/1/30
- arXiv:
- arXiv:1105.4761
- Bibcode:
- 2011ApJ...737...30O
- Keywords:
-
- radio continuum: stars;
- stars: individual: Cyg OB2 #5;
- stars: winds;
- outflows;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted for publication in The Astrophysical Journal