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The discovery of very red counterparts to faint X-ray sources

A. M. Newsam·I. M. McHardy·L. R. Jones·K. O. Mason
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Abstract

We present deep K-band imaging at the positions of four very faint X-ray sources found in the UK ROSAT Deep Survey to have no optical counterpart brighter than R~23. Likely identifications are found within the ROSAT error circle in all four fields with R-K colours of between 3.2 +/- 0.4 and 6.4 +/- 0.6. From a consideration of the R-K colours and X-ray to optical luminosity ratios of the candidate identifications, we tentatively classify two of the X-ray sources as very distant (z ~ 1) clusters of galaxies, one as a narrow emission line galaxy and one as an obscured QSO.

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A. M. Newsam, I. M. McHardy, L. R. Jones, K. O. Mason. 1997-08-25. The discovery of very red counterparts to faint X-ray sources. https://doi.org/10.1093/mnras%2F292.2.378

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