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This work provides a statistical analysis of the massive star binarycharacteristics in the Cygnus OB2 Association using radial velocity informationof 114 B3-O3 primary stars and orbital properties for the 24 known binaries. Wecompare these data to a series of Monte Carlo simulations to infer theintrinsic binary fraction and distributions of mass ratios, periods, andeccentricities. We model the distribution of mass ratio, log-period, andeccentricity as power-laws and find best fitting indices of alpha=0.1+/-0.5,beta=0.2+/-0.4, and gamma=-0.6+/-0.3 respectively. These distributions indicatea preference for massive companions, short periods, and low eccentricities. Ouranalysis indicates that the binary fraction of the cluster is 44+/-8% if allbinary systems are (artificially) assumed to have P<1000 days; if the power-lawperiod distribution is extrapolated to 10^4 years, a plausible upper limit forbound systems, the binary fraction is ~90+/-10%. Of these binary (or higherorder) systems, ~45% will have companions close enough to interact during pre-or post-main-sequence evolution (semi-major axis ~/<4.7 AU). The perioddistribution for P<27 days is not well reproduced by any single power-law owingto an excess of systems with periods around 3-5 days (0.08-0.31 AU) and arelative shortage of systems with periods around 7-14 days (0.14-0.62 AU). Weexplore the idea that these longer-period systems evolved to produce theobserved excess of short-period systems. The best fitting binary parametersimply that secondaries generate, on average, ~16% of the V-band light in youngmassive populations. This means that photometrically based distancemeasurements for young massive clusters & associations will be systematicallylow by ~8% (0.16 mag in the distance modulus) if the luminous contributions ofunresolved secondaries are not taken into account.

An Updated Look at Binary Characteristics of Massive Stars in the Cygnus OB2 Association