Serendipitous EXOSAT sources in the region of the Coma cluster: Active Galactic Nuclei with steep X-ray spectra
Open Access
- 1 October 1985
- journal article
- research article
- Published by Oxford University Press (OUP) in Monthly Notices of the Royal Astronomical Society
- Vol. 216 (4) , 1043-1055
- https://doi.org/10.1093/mnras/216.4.1043
Abstract
A ~ 7-hr 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 shows that four of these are background AGN not associated with the cluster. At the sensitivity level of the EXOSAT exposure, we would have expected to detect only 0.01 background sources on the basis of the Einstein Medium Sensitivity Survey. We discuss ways of interpreting this result and in particular the possibility that the AGN detected in the EXOSAT field have a much softer average X-ray spectrum than that usually considered to be ‘canonical’.Keywords
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