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”.