ROSAT observations of the supernova remnant CTB 1

We present ROSAT PSPC observations of the supernova remnant CTB 1 (G116.9 +0.2). The remnant is detected for the first time in the X-ray region. The X-ray morphology places the remnant into the class of center-filled remnants with a centrally peaked X-ray emission profile and accompanying 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 coincident 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 supernova remnant that swept the area around CTB 1 clean. The appearance of the remnant is most easily explained by evaporating clouds. Projection effects caused by an asymmetric remnant are discussed as another, less plausible, explanation.