Einstein observations of the Rho Ophiuchi dark cloud - an X-ray Christmas tree
Abstract
The results obtained by an extensive Einstein Observatory investigation of the Rho Ophiuchi dark cloud region, emphasizing the findings pertaining to the densest part of the cloud. The observations and specific features of the data analysis are briefly described, and the space distribution of the sources in the cloud is discussed, emphasizing the specific nature of the sources as highly variable X-ray objects. Observations of one remarkably variable source are discussed in detail, and the time variability of the source is interpreted as due to strong and widespread flare activity. One extreme case may be the strongest stellar X-ray flare ever recorded. Several implications bearing on early stages of stellar evolution are discussed, as are some consequences of the presence of active X-ray objects within dark clouds.