On the nature of sources of bursts of hard X-ray emission.

Observations of pulsed hard X-ray emission and gamma-ray bursts are briefly reviewed, and it is proposed that both types of radiation originate from the same sources. Several sources of pulsed hard X-ray emission observed by the Uhuru, Ariel 5, ANS, and Cosmos 428 satellites are identified with different globular clusters. Various gamma-ray bursts detected by the Vela satellites are identified with the globular clusters NGC 5694, NGC 4147, NGC 288, 47 Tuc, and NGC 1904. Black holes of 100 to 10,000 solar masses located within the globular clusters are suggested to be the cause of the pulses and bursts. Since some hard-radiation bursts have been observed in regions lacking globular clusters, it is concluded that the Galaxy may possess a peculiar population of 'invisible' globular clusters.