Searches for millisecond pulsations in low‐mass x‐ray binaries with Ginga data

Coherent millisecond x‐ray pulsations are expected from low‐mass x‐ray binaries (LMXB), but remain undetected. Using the single‐parameter Quadratic Coherence Recovery Technique (QCRT) to correct for unknown binary orbital motion we have performed Fourier transform searches for coherent oscillations in all long, continuous segments of data obtained at 1 millisecond time resolution during Ginga observations of LMXB. We have searched the six known Z‐sources (GX 5‐1, Cyg X‐2, Sco X‐1, GX 17+2, GX 340+0, and GX 349+2), seven of the ten known atoll sources (GX 3+1, GX 9+1, GX 9+9, 1728‐33, 1820‐30, 1636‐53, and 1608‐52), the ‘‘peculiar’’ source Cir X‐1, and the high mass binary Cyg X‐3. We find no evidence for coherent pulsations in any of these sources, with 99% confidence limits on the pulsed fraction between 0.3% and 5.0% at frequencies below the Nyquist frequency of 512 Hz.