On searches for pulsed emission with application to four globular cluster X-ray sources - NGC 1851, 6441, 6624, and 6712

We present the results of searches for periodic pulsations in the X-ray emission from four globular cluster sources, NGC 1851, NGC 6441, NGC 6624, and NGC 6712. The data were obtained by the Monitor Proportional Counter aboard HEAO 2 (Einstein Observatory). The methods of analysis are presented in some detail because we have correctly accounted for several effects which have been routinely overlooked by others. The periods searched cover the range from approx.1 ms to approx.500 s. No pulsed emission was detected, and the (90% confidence) upper limits for the pulsed fraction are presented.