Janine Fohlmeister, Christopher S. Kochanek, Emilio E. Falco, Joachim Wambsganss, Masamune Oguri, Xinyu Dai
We present 279 epochs of optical monitoring data spanning 5.4 years from January 2007 to June 2012 for the largest image separation (22."6) gravitationally lensed quasar, SDSS J1029+2623. We find that image A leads the images B and C by t_AB = (744 \pm 10) days, the uncertainty includes both statistical uncertainties and systematic differences due to the choice of models. With only a \sim1% fractional error, this is in the regime where uncertainties are dominated by fluctuations in the mean line-of-sight density compared to a smooth universe rather than the measurement. We cannot separate the fainter image C from image B, but since image C trails image B by only 2-3 days in all models, the estimate of the time delay between image A and B is little affected by combining the fluxes of images B and C. There is evidence for a low level of microlensing, perhaps created by whatever satellite is responsible for the flux ratio anomaly in this system. Interpreting the delay depends on better constraining the shape of the gravitational potential using the lensed host galaxy, other lensed arcs and the structure of the X-ray emission.
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http://arxiv.org/abs/1207.5776
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