Five more massive binaries in the Cygnus OB2 association

Abstract

We present the orbital solutions for four OB spectroscopic binaries, MT145, GSC 03161 - 00815, 2MASS J20294666+4105083, and Schulte 73, and the partial orbital solution to the B spectroscopic binary, MT372, as part of an ongoing study to determine the distribution of orbital parameters for massive binaries in the Cygnus OB2 Association. MT145 is a new, single-lined, moderately eccentric (e = 0.291 ± 0.009) spectroscopic binary with period of 25.140 ± 0.008 days. GSC 03161 - 00815 is a slightly eccentric (e = 0.10 ± 0.01), eclipsing, interacting and double-lined spectroscopic binary with a period of 4.674 ± 0.004 days. 2MASS J20294666+4105083 is a moderately eccentric (e = 0.273 ± 0.002) double-lined spectroscopic binary with a period of 2.884 ± 0.001 days. Schulte 73 is a slightly eccentric (e = 0.169 ± 0.009), double-lined spectroscopic binary with a period of 17.28 ± 0.03 days and the first "twin" in our survey with a mass ratio of q = 0.99 ± 0.02. MT372 is a single-lined, eclipsing system with a period of 2.228 days and low eccentricity (e ∼ 0). Of the now 18 known OB binaries in Cyg OB2, 14 have periods and mass ratios. Emerging evidence also shows that the distribution of log(P) is flat and consistent with "Öpik's Law." © 2009. The American Astronomical Society. All rights reserved.