Parallax and proper motion of Scorpius X-1

The absolute trigonometric parallax of the optical object identified with Sco X-1 is found to be Ir = -0"00l C)"006 (s.e.) as deterrnined from plates taken with the Yerkes Observatory 4() inch (102-cm) refractor. This suggests a distance to Sco X-1 greater than 200 pc. The absolute proper motion determined from these plates is = -o':oii I 0"006 per year and a = -0.018 I 0"003 per year (s.e.). This motion is consistent with reflex solar motion or membership in the Sco-Cen association and agrees with that deternnined by Sofia, Eichhorn, and Gatewood. However, Sco X-1 cannot he assumed to be a member of the association on the basis of proper motion alone, since the directions of the solar antapex and the motion of the assodation are almost coincident.