A 695 Hz quasi-periodic oscillation in the low-mass X-ray binary EXO 0748-676

We report the discovery of a 695 Hz quasi-periodic oscillation (QPO) in data taken with the Rossi X-Ray Timing Explorer of the low-mass X-ray binary (LMXB) EXO 0748-676. This makes EXO 0748-676 the second dipping LMXB, after 4U 1915-05, that shows kilohertz QPOs. Comparison with other sources suggests that the QPO corresponds to the lower frequency peak of the kilohertz QPO pair often observed in other LMXBs. The QPO was found in the only observation done during an outburst of the source in early 1996. This observation is also the only one in which the similar to 1 Hz QPO recently found in EXO 0748-676 is not present.