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We have monitored a sample of 27 nearby globular clusters in the hard X-rayband (20-120 keV) for approximately 1400 days using the BATSE instrument onboard the Compton Gamma-Ray Observatory. Globular clusters may contain a largenumber of compact objects (e.g., pulsars or X-ray binaries containing neutronstars) which can produce hard X-ray emission. Our search provides a sensitive(~50 mCrab) monitor for hard X-ray transient events on time scales of >1 dayand a means for observing persistent hard X-ray emission. We have discovered notransient events from any of the clusters and no persistent emission. Ourobservations include a sensitive search of four nearby clusters containing dimX-ray sources: 47 Tucanae, NGC 5139, NGC 6397, and NGC 6752. The non-detectionin these clusters implies a lower limit for the recurrence time of transientsof 2 to 6 years for events with luminosities >10^36 erg s^-1 (20-120 keV) and~20 years if the sources in these clusters are taken collectively. Thissuggests that the dim X-ray sources in these clusters are not transientssimilar to Aql~X-1. We also place upper limits on the persistent emission inthe range 2-10*10^34 erg s^-1 (2 sigma, 20-120 keV) for these four clusters.For 47 Tuc the upper limit is more sensitive than previous measurements by afactor of 3. We find a model dependent upper limit of 19 isolated millisecondpulsars (MSPs) producing gamma-rays in 47 Tuc, compared to the 11 observedradio MSPs in this cluster.Comment: 20 pages; accepted, ApJ; uu encoded tar file; 7 figure

A Search for Hard X-Ray Emission from Globular Clusters: Constraints from BATSE