An Intermediate-Mass Black Hole Candidate in the Globular Cluster GCl 2551
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GCl 2551 [RZ2004], an isolated globular cluster situated near M104, exhibits an intriguing X-ray emission with a luminosity of 3.23 Å~ 1037 erg/s. This emission is significantly higher than what is typically observed in globular clusters, prompting questions about its origin. One possible explanation is the presence of an intermediate-mass black hole (IMBH) at the cluster's core. To explore this hypothesis, the paper examines the characteristics of IMBHs and their expected X-ray emissions, comparing the observed luminosity of GCl 2551 to the Eddington luminosity for an IMBH. The findings indicate that the observed luminosity is below the Eddington limit, suggesting that if an IMBH is present, it is likely accreting at a sub-Eddington rate. The text also considers alternative sources for the X-ray emission, such as a population of low-mass X-ray binaries (LMXBs) or supernova remnants. However, the compact nature of the X-ray source and its location within a globular cluster strengthen the case for an IMBH. Further observations, including X-ray spectroscopy, variability studies, and multi-wavelength analyses, are recommended to confirm the presence of an IMBH in GCl 2551.
