Hardness-intensity diagram illustrating the spectral properties as a function of intensity for the X-ray point sources within the 5′ × 5′ field centred on Wd 1. The hardness colour is defined as (h − s)/(h + s) where h are the counts in the 2.0–8.0 keV band and s are the counts in the 0.5–2.0 keV band. Errorbars are not shown for reasons of clarity but are inversely correlated to flux and are given for individual sources in Table A.1. Two concentric rings denote comfirmed binaries, while one ring designates strong candidate systems (see Sect. 2). Blue and cyan symbols are O9-9.5 Iab,Ib,II,III and B0-0.5 Ia,Iab,Ib supergiants respectively, purple symbols are WRs and red symbols correspond to SB2 binaries of uncertain classification (Wd1-36 and -53a), binary products (Wd1-27 and -30a) the interacting binary Wd1-9 and eclipsing WNVL/BHG+OB system Wd1-13. We note that following the discussion in Sects. 2 and 3.2, Wd1-24 would also be included in this latter grouping if its binary nature were confirmed.