A search for high energy gamma-ray bursts from primordial black holes or other astronomical objects

Abstract

Two systems of separated atmospheric Cerenkov detectors have been used to search for bursts of high energy γ-rays which have been predicted theoretically from primordial black holes of about 10¹⁵ g in mass. In one experiment four 1.5-m reflectors were used with maximum separation 2.5 km. In another, two reflectors each of 70–80 m² in area, and separated by 400 km, were used in coincidence. Detection sensitivities for the latter were about 10⁻¹⁰ erg/cm² for bursts of less than 1 μs in duration, and γ-ray energies greater than 200 MeV. Using the Hagedorn nuclear model an upper limit of 0.04 events/pc³yr is set for the rate of black hole explosions in the Galaxy. Information can also be obtained on bursts of longer duration, which may occur if other nuclear models hold. The upper limits found are considerably larger than that for the Hagedorn model.