Spectral and temporal analysis of the first globular cluster black hole binary first black hole in a globular cluster

The first black hole binary in a globular cluster (XMMU 122939.7+075333) was discovered just over a decade ago in NGC 4472 and has consistently been found to have luminosities in excess of 2E39 erg/s. The first black hole binary in a globular cluster (XMMU 122939.7+075333) was discovered just over a decade ago in NGC 4472 and has consistently been found to have luminosities in excess of 2E39 erg/s. We use deep X-ray data to study the spectral and temporal characteristics of this source. The source spectrum once again shows evidence for emission from highly ionised oxygen, O VIII. Although the source is an ultraluminous X-ray source (ULX), it does not show the characteristic exponential roll over in its spectrum at >2keV found in other well- studied ULXs. Instead, we find that most of the flux variability is due to change in flux below 0.7 keV,seen as strong flaring where the source brightens by nearly an order of magnitude over the course of a few hours. Several other such systems have been discovered in extragalactic globular clusters in the Fornax And Virgo Clusters. Studying these globular cluster ULX systems gives us a chance to explore, compare and contrast ULXs with different compact objects, magnetic properties and donor masses, thereby leading to a greater understanding of this heterogeneous class of bright X-ray sources.