Special Astrophysics Seminar

Multiwavelength Studies of Ultraluminous X-Ray Sources in Extragalactic Globular Clusters

Kristen Dage

Michigan State University

The question whether globular clusters host black holes has been of longstanding interest. This interest has grown dramatically with the LIGO detection of merging black holes, as black hole mergers formed in globular clusters is one of the leading explanations for these LIGO sources. Determining whether black holes are common in globular clusters (GCs) has been an observational challenge. One of the most successful ways to identify candidate black holes in globular clusters is to identify globular cluster X-ray sources with very high luminosities that are much greater than the Eddington limit for neutron stars. We have found a number of ultraluminous X-ray sources (ULXs) within extragalactic globular clusters, which are candidate accreting black holes. These sources have a potential correlation between X-ray parameters of the sources and the presence of optical emission. One GC ULX has over ten years of both optical and X-ray monitoring, with the optical steadily declining over ten years before showing an increase. In this talk, I will discuss the search for new sources in other galaxies and multiwavlength studies of GC ULXs.