Forbidden oxygen lines in the spectra of UX Ori and RR Tau. Upper panel (a): [OI] 6300 Å lines in the spectra of UX Ori in the normal state with V = 9.98 mag on Sep. 5, 2020 (blue) and brightness minimum with V = 12.48 mag on Jan. 18, 2021 (red). Lower panel (b): The same as in the upper panel but for RR Tau with V = 10.66 mag on Oct. 5, 2019 (blue) and with V = 13.85 mag on Mar. 15, 2019 (red).