RZ2109 is a black hole candidate located in a globular cluster (GC) near NGC 4472. It is an ultraluminous X-ray source (ULX), meaning that its X-ray luminosity greatly exceeds the Eddington limit for a neutron star. We have analyzed new and archival data in both optical and x-ray, going back to the year 2000. Previous work indicates it is likely to be an ultra compact x-ray binary; the presence of the completely forbidden [OIII] transition line in the optical points towards the binary companion being a white dwarf. We hope that long-term optical and x-ray monitoring of this unique object will help shed light on the nature of the source. This is a very exciting object to study! The combination of the strong [OIII] line and the strongly variable, as well as the X-ray brightness make RZ2109 very different from other known globular cluster X-ray sources.
Globular Cluster ULXs
We conducted detailed X-ray analysis of eight more of the known GC ULXs besides RZ2109 by analyzing their spectra over years using data from the Chandra X-ray Observatory.
We were specifically interested in how they vary both long and short-term. This python notebook shows how we can quantify variability in the X-ray luminosity of a source.
As an undergraduate project, Will Clarkson and I looked for a link between the change in the super-orbital period and the change in the pulse period of the high mass X-ray binary SMC X-1. We compared the residuals in the pulse periods to the change over time of the super-orbital period. There is a compelling link between the two, which would imply that the neutron star is sensitive to and responding to changes in the configuration of the accretion disk.