Cosmic rays in the Magellanic clouds

Abstract

EGRET data from the Compton Gamma Ray Observatory have been used to determine the flux of gamma rays from the Small Magellanic Cloud (SMC). When compared with data at other wavelengths it is found that the parents of the gamma rays, the initiating cosmic rays (CRs), are concentrated much more strongly than is the case for the Large Magellanic Cloud (LMC). A consequence is that unless a single discrete gamma-ray source is responsible, the efficiency of CR production and/or trapping in the SMC is higher than would have been expected on the basis of the LMC results; there is also a hint that the SMC may be relatively richer in CR protons than the LMC.

The contribution of pulsars to diffuse gamma-rays in the Large Magellanic Cloud

“…If we assume that the same processes occur in the SMC, we can obtain that the -ray integral flux with energy greater than 300 MeV from the pulsars in the SMC is #8.6 10 29 cm 22 s 21 . Compared to the observed value of (2.2<0.7) 10 28 cm 22 s 21 (Al-Dargazelli et al 1996b), we obtain that the #39 per cent of the observed -rays for E P300 MeV in the LMC come from the pulsars. Therefore, we may conclude that pulsar contribution in the SMC is also very important.…”