Galactic Center IRS 13E: Colliding Stellar Winds or an Intermediate-mass Black Hole?

Abstract

A small cluster of massive stars residing in the Galactic center, collectively known as IRS 13E, is of special interest due to its close proximity to the central supermassive black hole Sgr A* and the possibility that an embedded intermediate-mass black hole (IMBH) binds its member stars. It has been suggested that colliding winds from two member stars, both classified as Wolf–Rayet type, are responsible for the observed X-ray, infrared, and radio emission from IRS 13E. We have conducted an in-depth study of the X-ray spatial, temporal, and spectral properties of IRS 13E, based on 5.6 Ms of ultradeep Chandra observations obtained over 20 years. These X-ray observations show no significant evidence for source variability. We have also explored the kinematics of the cluster members, using Keck near-infrared imaging and spectroscopic data on a 14 yr baseline that considerably improve the accuracy of the stars’ proper motions. The observations are interpreted using three-dimensional hydrodynamical simulations of colliding winds tailored to match the physical conditions of IRS 13E, leading us to conclude that the observed X-ray spectrum and morphology can be well explained by the colliding wind scenario, in the meantime offering no support for the presence of a putative IMBH. An IMBH more massive than a few 10 3 M ⊙ is also strongly disfavored by the stellar kinematics.