Surprising Variability of the Planetary Nebula IC 4997 $$=$$ QV Sge
Journal: Astronomy Letters
Year: 2020

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 has got redder from $$0\overset{m}{.}4$$ in 2000 to $$0\overset{m}{.}7$$ in 2019, whereas the $$U-B$$ color has not changed significant