Gamma-Ray Production in the Winds of Wolf-Rayet Stars

Abstract

The highly successful missions of the American SAS II (30-200 MeV) and European Cos-B (70 MeV - 5 GeV) orbiting γ-ray detectors showed that the diffuse gamma-ray sky correlates with the galactic disk structure (Mayer-Hasselwander et al. 1980), on which there are a number of sources superimposed with typical error boxes of 1° and typical flux of F _γ ~ 10^-6 ph.cm ^-2 s ^-1. On a large scale these sources show a correlation with the galactic arms (Caraveo & Paul 1979), and their latitude distribution shows that their average distance from the sun is between 2 and 5 kpc, with corresponding luminosities L _γ ~ 10³⁴ - 10³⁵ erg s ^-1 (Swanenburg et al. 1981). It was shown that up to 50% of the detected sources could be linked to active star forming regions, which includes the ρ Oph dark cloud complex (D ~ 160 pc) (Cassé & Paul 1980), the Orion complex (D ~ 500 pc) (Caraveo et al. 1980) and possibly also supernova remnants physically linked with OB associations (Montmerle 1979). Cassé & Paul (1980) showed that these objects show a substantial enhancement in cosmic ray (CR) intensity relative to the Solar neighborhood and they suggested that most of the observed cosmic rays in these objects may be accelerated in the expanding atmospheres of mass-losing stars, rather than by supernova (SNR) shock waves, which has been advocated by Montmerle (1979) to explain these γ-ray sources.