RVs & V-band LCs of probable members of Cyg OB2

Situated at the heart of the "Cygnus X" complex of star-forming regions and molecular clouds, its distance has proven elusive owing to the ambiguous nature of kinematic distances along this l~=80{deg} sightline and the heavy, patchy extinction. In an effort to refine the three-dimensional geometry of key Cygnus X constituents, we have measured distances to four eclipsing double-lined OB-type spectroscopic binaries that are probable members of Cyg OB2.

We find distances of 1.33+/-0.17, 1.32+/-0.07, 1.44+/-0.18, and 1.32+/-0.13kpc toward MT91 372, MT91 696, CPR2002 A36, and Schulte 3, respectively. We adopt a weighted average distance of 1.33+/-0.06kpc. This agrees well with spectrophotometric estimates for the Association as a whole and with parallax measurements of protostellar masers in the surrounding interstellar clouds, thereby linking the ongoing star formation in these clouds with Cyg OB2.