ROSAT OBSERVATIONS OF THE SUPERNOVA REMNANT CTB-1

We present ROSAT PSPC observations of the supernova remnant CTB 1 (G11 6.9 +0.2). The remnant is detected for the first time in the X-ray reg ion. The X-ray morphology places the remnant into the class of center- filled remnants with a centrally peaked X-ray emission profile and acc ompanying optical and radio shells. The emission is consistent with a thermal plasma with T=3 x 10(6) K and absorption N-H = 7 x 10(21) cm(- 2). A ''breakout'' along the northeast rim of the remnant is coinciden t with the position of an X-ray pulsar. A much larger feature appears to be a partial shell which may be associated with a previous supernov a remnant that swept the area around CTB 1 clean. The appearance of th e remnant is most easily explained by evaporating clouds. Projection e ffects caused by an asymmetric remnant are discussed as another, less plausible, explanation.