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Astron. Astrophys. 317, L13-L16 (1997)

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Letter to the Editor

RX J0911.4+0551: A new multiple QSO selected from the
ROSAT All-Sky Survey *

Norbert Bade 1, Joachim Siebert 2, Sebastian Lopez 1, Wolfgang Voges 2 and Dieter Reimers 1

1 Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg, Germany
2 MPI für Extraterrestrische Physik, D-85740 Garching, Germany

Received 19 September 1996 / Accepted 14 November 1996


We report from follow-up observations of high redshift AGN candidates from the ROSAT All-Sky Survey (RASS) that RX J0911.4+0551 is a gravitationally lensed QSO with [FORMULA]. With an X-ray luminosity of [FORMULA] it belongs to the X-ray brightest radio quiet QSOs. However, we must point out that the existing observations do not exclude the possibility that other objects inside the error circle are responsible for the X-ray flux, in particular a lensing cluster. Careful image analysis discerned three optical images. The separation between the two brighter components of [FORMULA] is below the seeing value during the observations. The fainter component has a distance of [FORMULA]. The spectra of the brighter joint A, B component and the C component show no measurable differences in continuum and absorption lines. Three strong CIV absorption line systems with [FORMULA] are visible in the spectra. All three have [FORMULA] which makes it improbable that they are caused by the lensing systems. The only spectral difference are larger equivalent widths of the broad emission lines in the brighter QSO components.

Key words: Quasars: general - Quasars: individual: RX J0911.4+0551 - Gravitational lensing

* Based on observations made at the European Southern Observatory, La Silla, Chile

Send offprint requests to: Norbert Bade

© European Southern Observatory (ESO) 1997