Extensive Air Shower Arrays as Detectors of Prompt Gamma Rays from Supernovae Explosions

Abstract

SUPERNOVAE explosions with total energies of 10⁴⁹ to 10⁵² ergs constitute the most energetic single events in our galaxy^1,2. Pulsars, which now appear to be rotating neutron stars formed in supernovae, contain similar amounts of energy^3,4, and it is believed that a large portion of this energy goes into accelerating relativistic particles, producing cosmic rays^3–5. The acceleration mechanism models fall into two general classes: the gradual transfer of rotational energy through electromagnetic channels to particles^4,6, and the shock wave hypothesis where most of the cosmic rays are accelerated during the initial explosion as the outer layers of the star are blown out at relativistic speeds^5,7. As a consequence of the shock wave acceleration mechanism Colgate has shown that a burst of photons of total energy 5 × 10⁴⁷ ergs per decade should accompany the explosion. The time width of this pulse is a fraction of a microsecond at the maximum photon energy of few GeV and proportionally longer at lower energies⁸. An experiment designed to detect this type of pulse using the atmospheric fluorescence method has already achieved the sensitivity and operation time necessary to observe such pulses, with negative results as yet⁹.