Preprint Logo P69 November
2001


To be published in:
Astronomy & Astrophysics

A novel approach for extracting time-delays from lightcurves of lensed quasar images.

Ingunn Burud, 1,2, Pierre Magain, 1, Sandrine Sohy, 1, Jens Hjorth 3


1 Institut d'Astrophysique et de Géophysique de Liège, Avenue de Cointe 5, 4000 Liège, Belgium
2 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
3 Astronomical Observatory, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark

Abstract

     We present a new method to estimate time delays from light curves of lensed quasars. The method is based on 2 minimization between the data and a numerical model light curve. A linear variation can be included in order to correct for slow long-term microlensing effects in one of the lensed images. An iterative version of the method can be applied in order to correct for higher order microlensing effects. The method is tested on simulated light curves. When higher order microlensing effects are present the time delay is best constrained with the iterative method. Analysis of a published data set for the lensed double Q~0957+561 yields results in agreement with other published estimates.

Key Words

Methods: data analysis - Gravitational lensing.

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