Investigating the origin of the X-ray emission of Cyg OB2 #5

Massive stars have strong winds, which collide in massive binaries, giving riseto hard and varying Xray emission. Cyg OB2 #5 is such a case. It was recentlyfound to be a quadruple system and changes in its X ray emission indicate thatXrays arise in the windwind collision (WWC) between the close binary and thethird star. In this context, Xrays are a crucial tool to constrain the orbitalparameters, but available observations only probe two phases of the 6.7 yr orbitof the third star. A monitoring (one observation per year) is thus needed and wetherefore request in this AO a short exposure observation (10 ks) to betterunderstand this iconic system. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]