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Surprising Variability of the Planetary Nebula IC 4997 = QV Sge

Arkhipova, V. P.; Esipov, V. F.; Ikonnikova, N. P. +3 more

We present the results of a new epoch (2009-2019) of a long-term (50 years) photometric monitoring of the variable planetary nebula IC 4997 (QV Sge). The integral (star + nebula) $UBV$ light curves display a continuing brightening of $0\overset{m}{.}15$ in $V$, a slight rise (${<}0\overset{m}{.}1$) in $B$, and constancy in $U$. The $B-V$ color …