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

Letter to the Editor

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

V. Discovery of a 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 <sup>3

1</sup> 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

Abstract

We report on the discovery of the first QSO in the  ROSAT All Sky Survey (RASS) near the X-ray source RX J1028.6-0844. From the Ly emission line found in an optical spectrum we measured . 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 = 8.33 10^-13 erg s^-1 cm^-2 and a luminosity of 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 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

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Contents

• 1. Introduction
• 2. Observational results
  • 2.1. RASS observations
  • 2.2. Optical observations
• 3. Discussion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: June 5, 1998

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