Local gamma rays and cosmic-ray acceleration by supersonic stellar winds

Abstract

Supersonic stellar winds are quite common among the brightest and/or the youngest stars, i.e., O stars and B supergiants, T Tauri stars, Herbig-Haro objects etc. It is proposed that the shocked region at the boundary between the stellar wind and the surrounding medium is, under certain conditions, the site of acceleration of charged particles with a power-law energy spectrum, extending a suggestion proposed by Jokipii for the solar wind. This mechanism should operate up to 10 to the 15th eV. On the basis of the Copernicus UV observations, it is suggested that the luminous OB stars pertaining to the Gould Belt are the major sources of local cosmic rays. Observational support to cosmic-ray acceleration by stellar winds in the Rho Oph cloud, based on high-energy gamma-ray observations performed by the COS B satellite are presented. A major consequence of these views is the peculiar character of our local galactic environment as far as cosmic rays are concerned.