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Optical observations of serendipitous EXOSAT sources in the Coma Cluster |
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| Authors: | G Branduardi-Raymont K O Mason P G Murdin C Martin S P McKechnie |
| Institution: | (1) Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, UK;(2) Royal Greenwich Observatory, Herstmonceux Castle, Hailsham, East Sussex, UK;(3) Instituto de Astrofisica de Canarias, La Laguna, Spain;(4) CRWG, Huygens Laboratorium, Wassenaarseweg 78, Leiden, The Netherlands |
| Abstract: | A  7 hour observation of the central part of the Coma Cluster of galaxies has been performed with the EXOSAT LE telescopes and CMA detectors. Five serendipitous sources are detected within the inner 35 arcmin radius of the field. Optical spectroscopy demonstrates that at least three of these are background AGN not associated with the cluster. At the sensitivity level of the EXOSAT exposure, we would have expected to see only 0.01 background sources based on the Einstein Medium Sensitivity Survey. The EXOSAT and Einstein results may be reconciled if these AGN have a much softer average X-ray spectrum than previously assumed. |
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