LCs & spectra of SDSS J1515+1511 lens system

These include a 2.6-year photometric monitoring with the Liverpool Telescope (LT) in the r band, as well as a spectroscopic follow-up with the LT and the Gran Telescopio Canarias (GTC). Our r-band LT light curves cover a quiescent microlensing period of the doubly imaged quasar at z_s_=2.049, which permits us to robustly estimate the time delay between the two images A and B: 211+/-5d (1{sigma} confidence interval; A is leading).

Unfortunately, the main lensing galaxy (G1) is so faint and close to the bright quasar that it is not feasible to accurately extract its spectrum through the GTC data. However, assuming the putative redshift z_G1_=0.742, the GTC and LT spectra of the distant quasar are used to discuss the macrolens magnification, and the extinction and microlensing effects in G1. The new constraints on the time delay and macrolens magnification ratio essentially do not change previous findings on the mass scale of G1 and external shear, while the redshift of the lensing mass is found to be consistent with the assumed value of z_G1_.