Identification of a complete sample of northern ROSAT All-Sky Survey X-ray sources .2. The optical observations

We describe a program for the optical identification of a representative sample of RASS sources contained in six study areas north of delta = -9 degrees, with \b(II)\ greater than or similar to 20 degrees including one region near the North Galactic pole ((NGP) and one near the North Ecliptic pole (NEP) and present some preliminary results. A full identification has been carried out for a count-rate and area-limited complete subsample comprising 674 sources. The ratio of ''extragalactic'' ( e.g. AGN, clusters of galaxies) to ''stellar'' (e.g. coronal emitters, active binaries) counterparts was found to depend on the galactic neutral hydrogen column density, N-H. In the area near the NGP (low N-H) ''extragalactic'' counterparts dominate, while in the area with the highest N-H most X-ray sources are identified with stellar counterparts.