Dim x‐ray sources in globular clusters

Recent results are reviewed from sensitive x‐ray observations of globular clusters with ROSAT. It is clear that virtually all globulars contain a ‘‘core source’’ with soft x‐ray luminosity of ∼1032.5 erg/s, thus confirming the original Einstein Observatory discovery of such ‘‘dim sources’’ within globular clusters. High Resolution X‐ray images (HRI) with ROSAT show that these sources can be resolved into ≳3–5 sources with correspondingly reduced luminosities. High resolution optical images with HST in Hα vs. R are reviewed and show that emission line objects with uv excesses are found within the ≲6‘ positional uncertainties of the dim x‐ray sources in NGC 6397 and possibly also NGC 6752. The distinction between CVs and quiescent LMXBs is discussed, as well as additional constraints imposed by the dim sources in globulars. The overall results now becoming available from high resolution imaging with ROSAT (HSI) and HST argue that CVs have finally been discovered in globular clusters.