The very slow nova PU Vul was discovered by Honda and Kuwano in 1979 after the rise from B ~ 15…16 mag to a maximum B ~ 9 mag. The object has been studied by many authors (for references see Belyakina et al. 1989; Vogel & Nussbaumer 1992) but a clear picture of the system was not given. Two minima of different duration were observed in the system in the active stage, in 1980-81 and 1993-94 (Kolotilov et al. 1995). Nussbaumer & Vogel (1996) ascribed the minima to eclipses of the hot component by the cool M giant in a binary with orbital period of 4900±100 d. Our period analysis of the preoutburst B data (Liller & Liller 1979) by Stellingwerf’s (1978) method revealed a period of 4858 d. We found the third minimum in 1926-28 (lasting for 500…630 d) in these data.
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