This work, focused on the description and understanding of the nature of a [O III]emission line source associated with an accreting stellar mass black hole in a globlar cluster,is comprised of three papers.In the first paper, we present a multi-facility study of the optical spectrum of the extra-galactic globular cluster RZ2109, which hosts a bright black hole X-ray source. The opticalspectrum of RZ2109 shows strong and very broad [O III]λλ4959,5007 emission in additionto 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 thatthe equivalent width of the lines is similar in all of the datasets; the change in L[O III]λ5007is ≤ 10% between the first and last observations, which were separated by 467 days. Thevelocity profile of the line also shows no significant variability over this interval. Using a simple geometric model we demonstrate that the observed [O III]λ5007 line velocity structurecan be described by a two component model with most of the flux contributed by a bipolarconical outflow of about 1,600 km s−1 , and the remainder from a Gaussian component with a FWHM of several hundred km s−1 .In the second paper, we present an analysis of the elemental composition of the emission line system associated with the black hole hosting globular cluster RZ2109 located inNGC4472. From medium resolution GMOS optical spectroscopy we find a [O III]λ5007/Hβemission line ratio of 106 for a 3200 km s−1 measurement aperture covering the full velocity width of the [O III]λ5007 line, with a 95% confidence level lower and upper limitsof [O III]λ5007/Hβ > 35.7 and < −110 (Hβ absorption). For a narrower 600 km s−1aperture covering the highest luminosity velocity structure in the line complex, we find[O III]λ5007/Hβ = 62, with corresponding 95% confidence lower and upper limits of > 30.2and < −364. The measured [O III]λ5007/Hβ ratios are significantly higher than can beproduced in radiative models of the emission line region with solar composition, and theconfidence interval limits exclude all but the most extremely massive models. Therefore, weconclude that the region from which the [O III]λ5007 emission originates must be hydrogendepleted relative to solar composition gas. This finding is consistent with emission from anaccretion powered outflow driven by a hydrogen depleted donor star, such as a white dwarf,being accreted onto a black hole.In the third paper, we examine the variability of the [O III]λλ4959,5007 emission linesource in the NGC 4472 black hole hosting globular cluster RZ2109. Our continuing multi-facility monitoring program finds the strong emission line source had decreased 24±2 percentfrom the 2007-2010 mean levels in 2011 and 40±5 percent from the earlier mean in 2012. Ananalysis of the variability of the emission line velocity profile finds that the flux ratio of highervelocity 1600 km s−1 component to the lower velocity 300 km s−1 component has decreased30 percent from 2009 to 2011, and the asymmetry between the red and blue wings of theprofile has decreased 17 percent. We compare this variability to predictions of photoionizednova ejecta models of the emission line region, and discuss its implications for an accretionpowered outflow from a CO WD-BH bianry model.
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