The discovery of a 97 minute periodicity in 4U 1700-37

SAS 3 observations of a complete orbital cycle (about 3.5 days) of the X-ray source 4U 1700-37 are presented. A persistent, approximately sinusoidal modulation of about 60% amplitude is present in the data at 97 minutes. Satellite orbital effects are ruled out by using other detectors pointed away from the source but sampled at the same time. The effect of such a long rotation period (if indeed the period is rotational) on current ideas involving accretion torques and stellar wind is discussed.