Astron. Astrophys. Suppl. Ser. 132, 341-359

Identification of selected sources from the ROSAT Galactic Plane Survey. I.

C. Motch ¹ - P. Guillout ^2,1 - F. Haberl ² - J. Krautter ³ - M.W. Pakull ¹ - W. Pietsch ² - K. Reinsch ⁴ - W. Voges ² - F.-J. Zickgraf ¹

Send offprint request: C. Motch

1 - Observatoire Astronomique, UMR 7550 CNRS, 11 rue de l'Université, F-67000 Strasbourg, France
2 - Max-Planck-Institut für extraterrestrische Physik, D-85740, Garching bei München, Germany
3 - Landessternwarte, D-69117 Heidelberg-Königstuhl, Germany
4 - Universitäts-Sternwarte, Geismarlandstrasse 11, D-37083, Göttingen, Germany

Received December 9, 1997; accepted April 30, 1998

Abstract:

We report on optical searches in the error circles of 93 ROSAT survey sources located at low galactic latitudes (|b| < 20$^\circ$). These sources were extracted from the ROSAT Galactic Plane Survey using various selection criteria on hardness ratio, X-ray and optical brightness and integrated galactic absorption in the direction of the source. We find optical identifications in 76 cases, among which are 25 new AGN, 6 new CVs and a new Be/X-ray binary. In order to illustrate the relevance of the source selections applied here, we cross-correlated the ROSAT all-sky survey bright source list with SIMBAD. Different classes of X-ray emitters populate distinct regions of a multi dimensional parameter space involving flux ratios, galactic latitude and $N_{\rm H}$. This relatively good segregation offers the possibility to build source samples with enhanced probability of identification with a given class. Complete optical identification of such subsamples could eventually be used to compute meaningful probabilities of identification for all sources using as basis a restricted set of multi-wavelength information.

Key words: X-ray general -- X-ray stars -- X-rays: galaxies -- surveys