X-ray observations of the Cygnus Loop by ANS

Detailed X-ray brightness distributions in the 0.16-0.284 keV, 0.32-0.46 keV, and 1-2.5 keV energy ranges are presented for the Cygnus Loop, using ANS satellite observations. Spectral fits to the data yield temperature and interstellar hydrogen column density variations on a scale of 30 arcmin x 40 arcmin. Some general parameters are derived from the composite spectrum, and attention is given to the coronal lines of Fe X and Fe XIV, as well as to the upper limit to O VII line emission. The temperature ranges from about 1,000,000 to 5,000,000 deg K, and the column density varies in the range of 1-12 x 10 to the 20th atoms per sq cm. Large variations (0.1-2 per cu cm) in the density of the ambient interstellar medium were also derived. It is concluded that the soft X-ray emission of the Cygnus Loop is concentrated in the north and north-east region, and that a large cloud with a depth of at least 20 pc is present in front of the source; in addition, a clear separation is determined between NGC 6992 and NGC 6995.