The harmonic and sideband structure of the kilohertz quasi-periodic oscillations in Sco X-1

We use data from the Rossi X-ray Timing Explorer to search for harmonics an d sidebands of the two simultaneous kilohertz quasi-periodic oscillations ( kHz QPOs) in Sco X-1. We do not detect any of these harmonics or sidebands, with 95 per cent confidence upper limits to their power between similar to 1 and similar to 10 per cent of the power of the upper kHz QPO. The oscilla tions produced at these frequencies may be attenuated in a scattering coron a around the neutron star. We find that upper limits to the unattenuated po wer of some of the strongest theoretically predicted harmonics and sideband s are as low as similar to2 per cent of the unattenuated power of the high- frequency QPO in Sco X-1.