  We present the discovery of [OIII] 5007 emission associated with the black
hole X-ray binary recently identified in a globular cluster in the Virgo
elliptical galaxy NGC 4472. This object is the first confirmed black-hole X-ray
binary in a globular cluster. The identification of [OIII] 5007 emission from
the black-hole hosting globular cluster is based on two independent fiber
spectra obtained at the VLT with FLAMES, which cover a wavelength range of
5000-5800 Angstrom at a spectral resolution of about 6000. In each of these
spectra we find an emission line at 5031.2 Angstrom with an uncertainty of
several tenths of an Angstrom. These are consistent with [OIII] 5007 emission
at the 1475 +/- 7 km/s radial velocity of the globular cluster previously
determined from an analysis of its absorption lines. This agreement within the
small uncertainties argues strongly in favor of the interpretation of the line
as [OIII] 5007 emission from the black-hole hosting globular cluster. We also
find that the emission line most likely has a velocity width of several hundred
km/s. Such a velocity width rules out a planetary nebula explanation for the
[OIII] 5007 emission and implicates the black hole as the source of the power
driving the nebular emission.
