Discovery of a Periodic Pulsating Binary X-Ray Source in Hercules from UHURU

We have discovered a new pulsating X-ray source with a 1.24 period in the constellation Hercules. Analysis of 5 months of data has shown the existence of periodic variations in the intensity of the source and correlated sinusoidal variations in the period of the 1.24 pulsations. As in the case of the pulsating X-ray source Cen X-3, we interpret this effect as due to an occulting binary system, with the intensity changes due to occultation of the X-ray source by its companion and with the sinusoidal variations in the period of the 1.24 pulsations due to the Doppler effect. The orbital period for the X-ray source is 1d.700l7 * 0d.00004, and the time of occurrence of the center of occultation is UT (1972 January 13.0772 * 0.0003) * n(1.70017 * 0.00004). In addition, we have observed a longer-timescale cycle in which the source is bright and pulsing for approximately 9 days during which we can observe the ld.7 occulting, followed by approzimately 27 days during which the source is not detected above background on individual 20-s scans.