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Our photometric and spectroscopic monitoring shows that starting with 2020June 4, day +217 from optical maximum and well into its advanced nebular stage,Nova Sct 2019 began displaying a series of nine large amplitude flares (up toDelta(m)~1.7 mag), characterized by a rapid rise to peak (=<10 hours) and afast exponential decline (e-folding time =<50 hours). The time intervalDelta(t) between flares follows an ordered sequence, declining from 8.43 to4.90 days, that safely allows to exclude that any other flare occured withoutbeing recorded by the observations. When the sequence of flares was over by2020 July 28 (day +271), Nova Sct 2019 slowed its overall decline rate fromDelta(m)=0.0067 mag/day to 0.0027 mag/day. The flares were caused by materialexpelled at high velocity (~1000 km/s) from the still burning WD. The coolerpseudo-photosphere forming at each flare in the expelled material, resulted ina recombination wave to spread through the original nova ejecta (at ~170 AUfrom the WD), quenching emission from [FeX] and [FeVII] and boosting that fromlower ionization species. After each flare, once the small amount of expelledmaterial had turned optically thin, the original nova ejecta resumed displaying[FeX] and [FeVII] emission lines, a fact that clearly proves the directphoto-ionization action exerted on the ejecta by the burning WD. While theother known flaring novae (V458 Vul, V4745 Sgr, and V5588 Sgr) presented theflares close to maximum brightness and with increasing Delta(t), Nova Sct 2019is unique in having displayed them during the advanced nebular stage and withdecreasing Delta(t).

Multiple flares caused by mass ejection episodes during the advanced nebular phase of Nova Scuti 2019