Double gravitationally lensed quasar J1721+8842 observed at the Maidanak observatory

This paper presents the results of observations and the light curve of the unique doubly gravitationally lensed quasar J1721+8842, observed at the Maidanak observatory from 2018 to 2024. It also includes the results of best image reduction using a deconvolution method that separates 6 lensed point-like images. Based on recent observations from space telescopes and related studies, a lensing model for quasar J1721+8842 involving two lensing galaxies is proposed. This two-lens model accounts for the formation of 6 point-like lensed images of the distant quasar, as well as the appearance of red arc-like structures, which result from the lensing of a distant red galaxy by a closer elliptical galaxy.