Velocity Structure and Variability of [O III] Emission in Black Hole
  Host Globular Cluster RZ2109
  We present a multi-facility study of the optical spectrum of the
extragalactic globular cluster RZ2109, which hosts a bright black hole X-ray
source. The optical spectrum of RZ2109 shows strong and very broad [O
III]\lambda \lambda 4959,5007 emission in addition to the stellar absorption
lines typical of a globular cluster. We use observations over an extended
period of time to constrain the variability of these [O III] emission lines. We
find that the equivalent width of the lines is similar in all of the datasets;
the change in L[O III]\lambda 5007 is \ltsim 10% between the first and last
observations, which were separated by 467 days. The velocity profile of the
line also shows no significant variability over this interval. Using a simple
geometric model we demonstrate that the observed [O III]\lambda 5007 line
velocity structure can be described by a two component model with most of the
flux contributed by a bipolar conical outflow of about 1,600 km/s, and the
remainder from a Gaussian component with a FWHM of several hundred km/s.
