A Black Hole in the Galactic Center Complex IRS 13E?

The IRS 13E complex is an unusual concentration of massive, early-type starsat a projected distance of ~0.13 pc from the Milky Way's central supermassiveblack hole Sagittarius A* (Sgr A*). Because of their similar proper motion andtheir common nature as massive, young stars it has recently been suggested thatIRS 13E may be the remnant of a massive stellar cluster containing anintermediate-mass black hole (IMBH) that binds its members gravitationally inthe tidal field of Sgr A*. Here, we present an analysis of the proper motionsin the IRS~13E environment that combines the currently best available data witha time line of 10 years. We find that an IMBH in IRS 13E must have a minimummass of ~10^4 solar masses in order to bind the source complex gravitationally.This high mass limit in combination with the absence so far of compellingevidence for a non-thermal radio and X-ray source in IRS 13E make it appearunlikely that an IMBH exists in IRS 13E that is sufficiently massive to bindthe system gravitationally.