HST and ground-based observations of the gravitational lens system Q1009-0252 A & B

In this paper, we propose a critical study of direct images and spectra obtained for the doubly imaged QSO Q1009-0252 A & B (=LBQS1009-0252 A & B). First, we report new observations with the WFPC2 onboard the Hubble Space Telescope (HST), in which the lensing galaxy is very clearly detected. We combine these with existing NICMOS observations in order to characterize the nature and redshift of the lens. Our HST observations are also fitted with simple analytical lens models; estimates expected for the time delay and M/L of the lensing galaxy are derived. Secondly, new and existing ground-based observations are used in order to establish the first multicolour lightcurves of the lensed components. Although the time resolution is low, flux variability is detected for both components. Finally, ground-based spectroscopic observations published by Surdej et al. (1993) are re-processed with a new method designed to extract spectra with small angular separations. The final spectra are analysed on the basis of a simple model including macrolensing and microlensing amplifications and dust extinction.