Old Q0957+561 data & software:
► Simple FORTRAN programs to apply the d2 test (accurate and robust time delay measurements)
► Photos
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SBS 0909+532
OPTICAL MONITORING: VR frames of SBS 0909+532 were used to obtain the first resolved light curves of the lens system and the first time delay between its two components A and B (Ullán et al. 2006). The observations in 2003 were carried out at Calar Alto Observatory, Maidanak Observatory (Uzbekistan) and Wise Observatory, and the global monitoring programme was conducted by the UC, IAKhNU (Kharkov, Ukraine), SAI (Moscow, Russia), UBAI (Uzbekistan) and TAU (Tel-Aviv, Israel) teams. New brightness records in the r band (LRT = Liverpool Robotic Telescope, 2005-2006) robustly confirmed the initial delay measurement. In the LEFT PANEL, we show the LRT fluxes of A (in red), shifted by - 49 days and + 0.651 mag, and the fluxes of B (in blue). The RIGHT PANEL includes the difference light curve, which is consistent with zero, i.e., there is no evidence for extrinsic variability.
(click on the figure to enlarge)
The structure function of the quasar intrinsic luminosity was also discussed by Goicoechea et al. (2007), who remarked the unique advantages of using gravitationally lensed quasars (GLQs) as a tool to study the origin of the intrinsic signal of quasars, because there is no way to disentangle intrinsic from extrinsic signal in a non-lensed quasar. New long term monitoring programmes of GLQs with flat difference curve will permit to fairly discuss the structure of the intrinsic variability on short and long timescales, and to compare between this behaviour and the structure of the fluctuations in both GLQs with non-flat difference curve and non-lensed quasars.
(click on the figure to enlarge)