THE FAINT X-RAY SOURCES IN AND OUT OF OMEGA-CENTAURI - X-RAY OBSERVATIONS AND OPTICAL IDENTIFICATIONS

We present the results of an observation of the globular duster omega Cen (NGC 5139) with the Einstein high-resolution imager (HRI). Of the five low-luminosity X-ray sources toward omega Cen which were first id entified with the Einstein imaging proportional counter (IPC) (Hertz a nd Grindlay 1983a, b), two are detected in the Einstein HRI observatio n: IPC sources A and D. These detections provide source positions accu rate to 3''4''; the positions are confirmed in a ROSAT HRI observation reported here. Using CCD photometry and spectroscopy, we have identif ied both sources as foreground dwarf M stars with emission fines (dMe) . The chance projection of two dMe stars within similar to 13' of the center of omega Cen is not extraordinary, given the space density of t hese stellar coronal X-ray sources. We discuss the possible nature of the three as yet unidentified IPC sources toward omega Cen, and consid er the constraints that the Einstein observations place on the total p opulation of X-ray sources in this cluster. The integrated luminosity from faint X-ray sources in omega Cen appears to be low relative to bo th the old open cluster M67 and the post-core-collapse globular, NGC 6 397.