COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses XIII: Time delays and 9-yr optical monitoring of the lensed quasar RX J1131-1231

Understand

We present the results from nine years of optically monitoring the gravitationally lensed z=0.658 quasar RX J1131-1231.

• The R-band light curves of the four individual images of the quasar were obtained using deconvolution photometry for a total of 707 epochs.
• Several sharp quasar variability features strongly constrain the time delays between the quasar images.
• Using three different numerical techniques, we measure these delays for all possible pairs of quasar images while always processing the four light curves simultaneously.