The Determination of the Proper Motions of X-Ray Sources

Extract

At the University of South Florida Observatory, a program is under way to determine the proper motions of the star-like objects which are possibly or probably associated with X-Ray sources. The objects under study are Sco X-l, and objects believed to be identical with Cen X-2, Cyg X-2, and Co D -32° 1057. Since it has been speculated that these might be neutron stars, an effort was made to study not only their proper motions but also those of other stars in the neighborhood to ascertain membership of any moving cluster with known age and distance, whereby their own ages and distances might become known. These efforts were successful so far in the case of ScoX-1 (Sofia, Eichhorn and Gatewood, 1969), whose proper motion is virtually identical to that which a member of theScorpio-Centaurus Association would have at this position, so that the membership of Sco X-l in this association becomes highly probable. On the basis of this and other information, Gatewood and Sofia (1969) conclude that Sco X-l is quite likely a neutron star. The reduction was described in detail by Gatewood (1968). No definitive results are available yet for the other three objects.