Evidence for a Stellar Disruption by an Intermediate-Mass Black Hole in an Extragalactic Globular Cluster

We report [O iii ] λ5007 and [N ii ] λ6583 emission from a globular cluster harboring the ultraluminous X-ray source CXOJ033831.8 − 352604 in the Fornax elliptical galaxy NGC 1399. No accompanying Balmer emission lines are present in the spectrum. One possibility is that the forbidden lines emanate from X-ray-illuminated debris of a star that has been tidally disrupted by an intermediate-mass black hole, with this debris also feeding the black hole leading to the observed X-ray emission. The line strengths indicate that the minimum size of the emitting region is ∼10 15 cm, and if the 70 km s −1 half-widths of the emission lines represent rotation around the black hole, a minimum black hole mass of 1000 M ☉ is implied. The non-detection of Hα and Hβ emission lines suggests a white dwarf star was disrupted, although the presence of strong nitrogen emission is somewhat of a mystery.