The listed position is that of the centroid of the X-ray source. Dec The Declination of the object. The listed position is that of the centroid of the X-ray source. LII The galactic latitude of the object. The galactic longitude of the object.
Negative offsets indicate directions west and south of the X-ray centroids.
Most of the offsets were measured automatically on the POSS or SRC J plates. For the SAO stars we have used the equinox 1950, epoch 1980 positions from the SAO catalog. When the optical counterpart is a cluster of galaxies, the optical offset refers to the brightest cluster member. Most of the offsets were measured automatically on the POSS or SRC J plates. For the SAO stars we have used the equinox 1950, epoch 1980 positions from the SAO catalog.