The ROSAT Galactic Plane Survey: Analysis of a low latitude sample area in Cygnus

The analysis of the part of the ROSAT all-sky survey covering the galactic plane is the scope of a de dicated project called the ROSAT Galactic Plane Survey. In order to statistically understand the nature of the ≈ 14 000 sources discovered by ROSAT at ≤ 20°, a number of sample areas have been chosen for follow-up optical identification. In this paper we present the X-ray and optical material gathered in a region located in the Cygnus constellation, centered at l = 90, b = 0and covering an area of 64.5deg2. A total of 95 and 128 sources are detected with a maximum likelihood larger than 10 and 8 respectively. With a typical survey exposure time of the order of 700 to 900 s the flux completeness level is ≈ 0.02 cts s-1corresponding to ≈ 2 10-13 erg cm-2 s-1. The position of the sample area allows to investigate the soft X-ray content of a rather typical region of the galactic plane. In this paper we describe the details of the observational procedures and data reduction. For each ROSAT source we list the main X-ray characteristics together with those of the proposed optical identification. When appropriate, we also show optical spectra and finding charts. The full analysis and discussion of these data are presented in a companion paper (Motch et al. 1997).