SPATIAL STRUCTURE OF THE CYGNUS LOOP IN THE X-RAY REGION ABOVE 1.5 KEV

We observed the Cygnus Loop with the large area counter on board Ginga in the energy range above 1.5 keV. The observation was performed in a scanning mode along two different directions: one parallel to and the other perpendicular to the Galactic plane. The spatial structure shows that the emission region above 1.5 keV is narrower than that below 1 keV while their centers coincide well with each other. Furthermore, it shows a center-filled structure (plerion-type) rather than a shell structure. The emission above 1.5 keV is not well correlated with the optical nebula. Our data show that a high-temperature, low-density plasma fills the interior of the Cygnus Loop and is surrounded by a low-temperature, high-density plasma shell. The luminosity above 1.5 keV from the plasma filled inside the Loop is 2 × 1033 ergs s-1 which is about 40 times stronger than that predicted with the strong shock model.