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We present the results of a deep ROSAT survey in the Leiden Berkeley Deep Survey field Lynx.3A, which has low $N_H$ and $E_{B-V}$. It has been well studied from the ground through deep Westerbork surveys (down to 17 $\mu$Jy at 1.4 GHz) {\it and} with the Palomar 200 inch Four-shooter CCD-array through a large contiguous mosaic in Gunn $gri$ with 90\% completeness to $B_J\sim$25.5 mag (Neuschaefer \& Windhorst 1995, ApJ 439, 000, in press).
We present the most likely optical candidates for the X-ray sources, as followed-up with the Kitt Peak 4 meter HYDRA multi-fiber and the Multiple Mirror Telescope's Red Channel spectrographs. Most ROSAT sources are stellar, and about two thirds of these have Gunn $gri$ colors typical of QSO's. The remainder are red objects, presumably X-ray stars. We also found a few compact galaxy ids, or galaxies in a group.
We also present the 0.5-2.0 keV source counts. At the bright end, the observed ROSAT/Lynx X-ray source counts have a slope and amplitude consistent with those of the Einstein Medium Sensitivity (EMSS) and Deep Surveys. At around $S_X \sim 10^{-14}$ cgs, our counts appear to flatten, in agreement with the results of two other ROSAT deep surveys. Below this level and down to our 3.5$\sigma$ completeness limit, the observed counts have a slope of 1.1$\pm$0.2. After correction for ``Eddington bias", our inferred intrinsic slope is 0.9$\pm$0.2, (at least marginally) flatter than the EMSS slope of 1.48$\pm$0.05 appropriate at brighter X-ray fluxes.
Our sample will be used to determine the AGN contribution to the XRB, as well as that of non-AGN (e.g. starburst and/or radio galaxies), and to constrain the evolution in radio--optical--X-ray of the primary X-ray population (AGN). This research is supported by NASA/ROSAT grant NAG-1455 and 2322.
