The gamma-ray source CG 353+16 : a supernova shock interacting with the cloud rho Ophiuchi.

It is suggested that the COS B gamma-ray source CG 353+16 may be the result of the acceleration of galactic cosmic rays by an old supernova shock wave and its interaction with the interstellar cloud Rho Ophiuchi. The supernova remnant in question is the North Polar Spur (Loop I). It is proposed that the shock wave of this remnant is in close proximity of the cloud. Cosmic rays are accelerated by the supernova shock in the hot interstellar medium, and the enhanced cosmic ray intensity is 'convected' with the shock. When the shock wave has reached the cloud, an unusually high gamma-ray emission results. Calculations show that the gamma-ray emission by CG 353+16 can be explained quite well by this process if the supernova remnant properties for Loop I inferred from X-ray observations are used.