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		| Paper: | 
		Multiplicity of massive O stars and evolutionary implications | 
	 
	
		| Volume: | 
		470, 370 Years of Astronomy in Utrecht | 
	 
	
		| Page: | 
		141 | 
	 
	
		| Authors: | 
		Sana, H.; de Mink, S. E.; de Koter, A.; Langer, N.; Evans, C. J.; Gieles, M.; Gosset, E.; Izzard, R. G.; Le Bouquin, J.-B.; Schneider, F. R. N. | 
	 
	
	
		| Abstract: | 
		Nearby companions alter the evolution of massive stars in binary systems.  Using a sample of Galactic massive stars in nearby young clusters, we simultaneously measure all intrinsic binary characteristics relevant to quantify the frequency and nature of binary interactions. We find a large intrinsic binary fraction, a strong preference for short orbital periods and a flat distribution for the mass-ratios. Our results do not support the presence of a significant peak of equal-mass ‘twin’ binaries.
 As a result of the measured distributions, we find that over seventy per cent of all massive stars exchange mass with a companion. Such a rate greatly exceeds previous estimates and implies that the majority of massive stars have their evolution strongly affected by interaction with a nearby companion. | 
	 
	
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