Оптические осцилляции активных ядер и сверхвысокое угловое разрешение гравитационно-линзированных квазаров SDSS J1721+8842, SDSS J1433+6007 и SDSS J2145+6345

The paper presents the results of the detection of active variability and optical oscillations of the general light curves of gravitationally lensed quasars SDSS J1721+8842, SDSS J1433+6007 and SDSS J2145+6345 for the period 2018−2020 based on observations from the Maidanak observatory. Based on the best observations from the AZT-22 telescope with a quality of seeing=0.6−0.7”, followed by digital processing, ultra-high angular resolution images with a value of FWHM=0.26” of individual lensed components and their light curves were obtained. Precision astrometry of individual lensed components was obtained, which made it possible to estimate the measurement accuracy of ±0.015”. The intrinsic active optical variability of the components of lensed quasars that characterize nonstationary processes and oscillations resulting from variable energy release in active nuclei and accretion disks around supermassive black holes is determined. The sequence of variables of the lensed components A-C-B-D of SDSS J1721+8842 with a time delay is determined: AC=−8.5±1.7 days, AB=−10.3±1.7 days, and AD=−18.7±2.8 days.