The faint X-ray sources in and out of omega Centauri: X-ray observations and optical identifications

Abstract

view Abstract Citations (15) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Faint X-Ray Sources In and Out of omega Centauri: X-Ray Observations and Optical Identifications Cool, Adrienne M. ; Grindlay, Jonathan E. ; Bailyn, Charles D. ; Callanan, Paul J. ; Hertz, Paul Abstract We present the results of an observation of the globular cluster 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 identified with the Einstein imaging proportional counter (IPC) (Hertz and Grindlay 1983a, b), two are detected in the Einstein HRI observation: IPC sources A and D. These detections provide source positions accurate to 3 sec-4 sec; the positions are confirmed in a ROSAT HRI observation reported here. Using CCD photometry and spectroscopy, we have identified both sources as foreground dwarf M stars with emission lines (dMe). The chance projection of two Mde stars within approximately 13 min of the center of omega Cen is not extraordinary, given the space density of these stellar coronal X-ray sources. We discuss the possible nature of the three as yet unidentified IPC sources toward omega Cen, and consider the constraints that the Einstein observations place on the total population of X-ray sources in this cluster. The integrated luminosity from faint X-ray sources in omega Cen appears to be low relative to both the old open cluster M67 and the post-core-collapse globular, NGC 6397. Publication: The Astrophysical Journal Pub Date: January 1995 DOI: 10.1086/175116 Bibcode: 1995ApJ...438..719C Keywords: Astrometry; Globular Clusters; Stellar Luminosity; X Ray Stars; Astronomical Photometry; Astronomical Spectroscopy; Charge Coupled Devices; Proportional Counters; Rosat Mission; Astronomy full text sources ADS | data products SIMBAD (8) HEASARC (1)