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Astron. Astrophys. 339, L73-L76 (1998)

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Letter to the Editor

First estimate of the time delay in HE 1104-1805 *

Lutz Wisotzki 1, Olaf Wucknitz 1, Sebastian Lopez 1 and Anton Norup Sorensen 2

1 Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, D-21029 Hamburg, Germany
2 Copenhagen University Observatory, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark

Received 2 September 1998 / Accepted 7 October 1998


We present first results from five years of spectrophotometric monitoring of the bright double QSO and gravitational lens HE 1104-1805. The quasar has varied considerably over this time, while the emission line fluxes appear to have remained constant. We have constructed monochromatic continuum light curves for components A and B, finding that B leads the variability. A quantitative analysis with the Pelt method gives a best estimate for the light travel time delay of about 0.73 years, although a value as low as 0.3 cannot yet be excluded. We discuss possible models for the QSO-lens configuration and use our measured time delay to predict the redshift of the lens, [FORMULA]. Finding that most likely [FORMULA], we can rule out the hitherto favoured values of [FORMULA] or 1.66. A new candidate is an absorption system at [FORMULA], but the lens could also be an elliptical not detected in absorption.

Key words: quasars: individual: HE 1104-1805 – quasars: general – gravitational lensing

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

Send offprint requests to: L. Wisotzki (lwisotzki@hs.uni-hamburg.de)

© European Southern Observatory (ESO) 1998

Online publication: October 22, 1998