X-ray emission from the field of the hyperluminous IRAS galaxy IRAS F15307+3252

We report on a 20-ks observation of the z = 0.93 hyperluminous galaxy IRAS F15307+3252 with the ROSATHRI. No X-ray source is detected at the position of F15307+3252 at an upper limit of similar to 4 x 10(43) erg s(-1). This is less than 2 x 10(-4) of the bolometric luminosity of the object, and indicates either that the nucleus emits an unusually small fraction of its total power in X-rays, or that little of the nuclear X-ray flux is scattered into our line of sight by electrons. The lack of an X-ray detection around F15307+3252 also rules out it being at the centre of a cluster, such as is observed for IRAS P09104+4109. A weak, possibly extended, X-ray source is detected 13 arcsec south of the galaxy, spatially coincident with a clump of faint objects visible in a Keck K-s-band image of the field. This may be the core of a cluster near the line of sight to F15307+3252.