EVIDENCE FOR A STELLAR DISRUPTION BY AN INTERMEDIATE-MASS BLACK HOLE IN AN EXTRAGALACTIC GLOBULAR CLUSTER

Abstract

We report [O III] 5007 Angstrom and [N II] 6583 Angstrom emission from a\nglobular cluster harboring the ultraluminous X-ray source (ULX)\nCXOJ033831.8-352604 in the Fornax elliptical galaxy NGC1399. No accompanying\nBalmer emission lines are present in the spectrum. One possibility is that the\nforbidden lines emanate from X-ray illuminated debris of a star that has been\ntidally-disrupted by an intermediate-mass black hole (IMBH), with this debris\nalso feeding the black hole leading to the observed X-ray emission. The line\nstrengths indicate that the minimum size of the emitting region is ~10^15 cm,\nand if the 70 km/s half-widths of the emission lines represent rotation around\nthe black hole, a minimum black hole mass of 1000 solar mass is implied. The\nnon-detection of H-alpha and H-beta emission lines suggests a white dwarf star\nwas disrupted, although the presence of strong nitrogen emission is somewhat of\na mystery.\n