X-Ray Localization of the Globular Cluster G1 with XMM-Newton

Abstract

We present an accurate X-ray position of the massive globular cluster G1 obtained using XMM-Newton and the Hubble Space Telescope (HST). The X-ray emission of G1 has been detected recently with XMM-Newton. There are two possibilities for the origin of the X-ray emission: it could be due to either accretion of the central intermediate-mass black hole, or ordinary low-mass X-ray binaries. The precise location of the X-ray emission might distinguish between these two scenarios. By refining the astrometry of the XMM-Newton and HST data, we reduced the XMM-Newton error circle to 1.5". Despite the smaller error circle, the precision is not sufficient to distinguish an intermediate-mass black hole or luminous low-mass X-ray binaries. This result, however, suggests that future Chandra observations may reveal the origin of the X-ray emission.