Ultrahigh-energy pulsed emission from Hercules X-1 with anomalous air-shower muon production

A search for bursts of air-shower events from Her X-1 at energies above 50 TeV during the calendar period April 2, 1986 to July 5, 1987 yielded two significant bursts, both occurring on July 24, 1986 (UT). The events during these bursts were pulsed with a period of 1.23568 sec, significantly different from estimates of the contemporaneous X-ray period. The probability that this represents random statistical fluctuations of the background is estimated to be 0.00002. The muon content of the burst events is anomalous when compared with expectations from gamma-ray showers. (Author)