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Astron. Astrophys. 323, L21-L24 (1997)

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Letter to the Editor

Identification of a complete sample of northern ROSAT All-Sky Survey X-ray sources

V. Discovery of a [FORMULA] QSO near the RASS source RX J1028.6-0844

F.-J. Zickgraf 1, W. Voges 1, J. Krautter 2, I. ThieringI. Appenzeller 2, 2, R. Mujica 3 and A. Serrano 3

1 Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, Postfach 1603, D-85740 Garching, Germany
2 Landessternwarte Königstuhl, D-69117 Heidelberg, Germany
3 Instituto Nacional de Astrofisica, Optica y Electronica, A. Postal 51 y 216 Z.P., 72000 Puebla, Mexico

Received 10 January 1997 / Accepted 22 April 1997


We report on the discovery of the first [FORMULA] QSO in the  ROSAT All Sky Survey (RASS) near the X-ray source RX J1028.6-0844. From the Ly [FORMULA] emission line found in an optical spectrum we measured [FORMULA]. This is so far the hightest redshift for a QSO in the RASS. The RASS X-ray count rate of 0.035 cts s-1 leads to an X-ray flux of [FORMULA] = 8.33 10-13 erg s-1 cm-2 and a luminosity of [FORMULA] [FORMULA] erg s-1 in the 2-10 keV rest frame energy band of the QSO if galactic column density of neutral hydrogen and a photon index [FORMULA] is assumed. The spectral energy distribution as inferred from the observed hardness ratios indicates the presence of considerable intrinsic absorption in the QSO around 2-2.5 keV.

Key words: Surveys – X-rays: general – X-rays: galaxies – (Galaxies:) quasars: general – Galaxies: active – (Galaxies:) quasars: emission lines

Present address: Observatoire Astronomique de Strasbourg, 11 rue de l'Université, F-67000 Strasbourg, France

Send offprint requests to: F.-J. Zickgraf

© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998