We present an r –band photometric monitoring of the two images A and B of the gravitationally lensed quasar SDSS J1442+4055 using the Liverpool Telescope ( LT ) .
From the LT light curves between 2015 December and 2018 August , we derive at once a time delay of 25.0 \pm 1.5 days ( 1 \sigma confidence interval ; A is leading ) and microlensing magnification gradients below 10 ^ { -4 } mag day ^ { -1 } .
The delay interval is not expected to be affected by an appreciable microlensing–induced bias , so it can be used to estimate cosmological parameters .
This paper also focuses on new Gran Telescopio Canarias ( GTC ) and LT spectroscopic observations of the lens system .
We determine the redshift of two bright galaxies around the doubly imaged quasar using LT spectroscopy , while GTC data lead to low–noise individual spectra of A , B , and the main lensing galaxy G1 .
The G1 spectral shape is accurately matched to an early–type galaxy template at z = 0.284 , and it has potential for further relevant studies .
Additionally , the quasar spectra show absorption by metal–rich gas at z \sim 2 .
This dusty absorber is responsible for an extinction bump at a rest–frame wavelength of 2209 \pm 2 Å , which has strengths of \sim 0.47 and 0.76 mag \mu m ^ { -1 } for A and B , respectively .
In such intervening system , the dust–to–gas ratio , gas–phase metallicity indicator [ Zn/H ] , and dust depletion level [ Fe/Zn ] are relatively high .