Evolution with phase of the relative distance between the contact binary system and the third star (top) and of their relative position (bottom) for the four orbital solutions proposed for Cyg OB2 #5 by Kennedy et al. (2010). The position angle is zero when the third star is in front of the binary, and 180° when the binary is in front of the third star. The circles indicate the position of the 2007 XMM-Newton observation (left side) and of the 2011 XMM-Newton observations (right side).