On the nature of the COSb-B gamma-ray source CG 353+16.

The recently proposed nearby (distance approximately 0.03 pc) cloud of Vidal-Madjar et al. (1978) has an angular extent encompassing the Rho Oph region and the COS-B CG 353+16 source. In an attempt to analyze a possible association between the gamma-ray source and the cloud, usage is made of SAS-3 low energy X-ray data to put an upper limit on the columnar density, and thus such an association can easily be excluded. Furthermore, the possibility is analyzed that the COS-B source is associated with the Rho Oph dark cloud complex, and that the responsible process is the interaction of cosmic rays with the cloud mass. It is seen that a standard Black and Fazio (1973) mechanism can hardly be at work so the quantitative requirements are given for an improved gamma-ray production rate, obtainable, for instance, within the model of Forman et al. (1979).