  X-ray and near-IR surveys of the central 2x0.8 degrees of the Galactic Centre
have revealed a population of X-ray bright massive stars. However, the nature
of the emission, originating in a wind collision zone or via accretion onto a
compact object, is uncertain. In order to address this we investigated the
nature of the luminous X-ray source CXOGC J174536.1-285638. An analysis of the
near-IR spectrum with a non-LTE model atmosphere code demonstrated that it was
an highly luminous WN9h star, for which comparison to evolutionary tracks
suggests an age of 2-2.5Myr and an initial mass of ~110Msun. The X-ray
properties of CXOGC J174536.1-285638 resemble those of 3 of the WN9h stars
within the Arches cluster and in turn other very massive WNLh colliding wind
binaries. Simple analytical arguments demonstrate consistency between the X-ray
emission and a putative WN9h+mid O V-III binary. However, we may not exclude a
high mass X-ray binary interpretation, which, if correct, would provide a
unique insight into the (post-SN) evolution of extremely massive stars.
Irrespective of the nature of the secondary, CXOGC J174536.1-285638 adds to the
growing list of known and candidate WNLh binaries. Of the subset of WNLh stars
subject to a radial velocity survey, we find a lower limit to the binary
fraction of ~45%; of interest for studies of massive stellar formation, given
that they currently possess the highest dynamically determined masses of any
type of star. [ABRIDGED]
