Follow-up obs. of the PSJ0147+4630 lens system

This recently discovered system mainly consists of four images ABCD of a background quasar around a foreground galaxy G that acts as a gravitational lens. First, we use long-slit spectroscopic data in the Gemini Observatory Archive and a multi-component fitting to accurately resolve the spectra of A, D, and G. The spectral profile of G resembles that of an early-type galaxy at a redshift of 0.678+/-0.001, which is about 20% higher than the previous estimate.

Additionally, the stellar velocity dispersion is measured to ~5% precision. Second, our early r-band monitoring with the Liverpool Telescope leads to accurate light curves of the four quasar images. Adopting time delays predicted by the lens model, the new lens redshift, and a standard cosmology, we report the detection of microlensing variations in C and D as large as ~0.1mag on timescales of a few hundred days.