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Astron. Astrophys. 335, 467-478 (1998)

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Identification of soft high galactic latitude RASS X-ray sources

I. A complete count-rate limited sample *

H.-C. Thomas 1, K. Beuermann 2, 3, K. Reinsch 2, A. D. Schwope 4, J. Trümper 3 and W. Voges 3

1 Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, D-85740 Garching, Germany
2 Universitäts-Sternwarte, Geismarlandstrasse 11, D-37083 Göttingen, Germany
3 Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse 6, D-85740 Garching, Germany
4 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany

Received 15 December 1997 / Accepted 31 March 1998


We present a summary of spectroscopic identifications for a complete sample of bright soft high galactic latitude X-ray sources drawn from the ROSAT All-Sky Survey which have PSPC count-rates CR [FORMULA] 0.5 [FORMULA] and hardness ratios HR1 [FORMULA]. Of a total of 397 sources, 270 had catalogued counterparts although most of these were not previously known as X-ray sources; of the remaining 127 sources neither X-ray nor optical properties were previously known. Of the whole sample of very soft X-ray sources 155 were also discovered by the Wide-Field-Camera on board ROSAT. We present spectroscopic identifications of 108 sources and other identifications for further 18 sources; 1 source remains unidentified so far. In practically all cases a unique optical counterpart exists facilitating identification. The largest source classes are AGN, magnetic cataclysmic variables, and hot white dwarfs.

Key words: X-rays: galaxies – X-rays: stars – galaxies: Seyfert – novae, cataclysmic variables – white dwarfs – stars: coronae

* Based in part on observations with the ESO/MPI 2.2m telescope at La Silla, Chile

Send offprint requests to: hcthomas@mpa-garching.mpg.de

© European Southern Observatory (ESO) 1998

Online publication: June 18, 1998