A Comment on X-Ray Source Identifications

The inherent difficulties in making X-ray/optical, X-ray/radio, and X-ray/X-ray identifications based solely on positional coincidents are discussed in regard to the third Uhuru catalog of X-ray sources. Handicaps in making identifications, such as the large uncertainties in positional determinants made from balloons and rockets, poor source separation in the crowded region toward the galactic center, source variability, and the multiplicity of source nomenclature, are described. Examples of confusing or spurious identifications are discussed, including 3U 1642-45 (correlated with G 339.6-0.1, GX 340+0, Ara-1, Ara X-1, and Ara XR-1) and Nor XR-1 (incorrectly correlated with Nor-1, Nor X-1, 3U 1624-49, 3U 1636-53, and 3U 1630-47).