Abstract
We propose to obtain the first Chandra image of the nearest very luminous (Lx~1e38-1e39 erg/s) recurrent supersoft X-ray source. The source, located in the spiral galaxy NGC 300, has a 5.4-hr period and is ultraluminous in the high state. The modest exposure time (15 ks with HRC-I) we request will provide an accurate X-ray position, allowing us to search for an optical counterpart and to better contrain the physical model of the system. We will also request 2 HST orbits to identify the counterpart. The HST images are deep enough to search for optical counterparts of X-ray binaries at the distance of NGC 300. If the nature of the companion star can be determined, it would conclude whether the compact object is an intermediate-mass black hole.