  Our photometric and spectroscopic monitoring shows that starting with 2020
June 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 to
Delta(m)~1.7 mag), characterized by a rapid rise to peak (=<10 hours) and a
fast exponential decline (e-folding time =<50 hours). The time interval
Delta(t) between flares follows an ordered sequence, declining from 8.43 to
4.90 days, that safely allows to exclude that any other flare occured without
being recorded by the observations. When the sequence of flares was over by
2020 July 28 (day +271), Nova Sct 2019 slowed its overall decline rate from
Delta(m)=0.0067 mag/day to 0.0027 mag/day. The flares were caused by material
expelled at high velocity (~1000 km/s) from the still burning WD. The cooler
pseudo-photosphere forming at each flare in the expelled material, resulted in
a recombination wave to spread through the original nova ejecta (at ~170 AU
from the WD), quenching emission from [FeX] and [FeVII] and boosting that from
lower ionization species. After each flare, once the small amount of expelled
material had turned optically thin, the original nova ejecta resumed displaying
[FeX] and [FeVII] emission lines, a fact that clearly proves the direct
photo-ionization action exerted on the ejecta by the burning WD. While the
other known flaring novae (V458 Vul, V4745 Sgr, and V5588 Sgr) presented the
flares close to maximum brightness and with increasing Delta(t), Nova Sct 2019
is unique in having displayed them during the advanced nebular stage and with
decreasing Delta(t).
