A balloon observation of a small cosmic X-ray burst

During the balloon observation performed on Sept. 27, 1970, a transient burst of X-rays was detected. This event was identified as a cosmic gamma-ray burst of a smaller size or at a larger distance than the Vela bursts observed over the X-ray energy range. The energy spectrum is consistent with that of some of the Vela bursts. The time profile of the event is qualitatively similar to the Apr. 27, 1972 event studied by Apollo 16. The detection of small bursts over the X-ray energy range by the balloon observation during a period of the order of 10 to 100 hours is not surprising, considering the probable frequency-size distribution of the burst.