  We assume that the strong convection during core helium flash of low mass red
giant branch (RBG) stars excite waves that propagate to the envelope, and find
that the energy that these waves deposit in the envelope causes envelope
expansion and brightening. We base our assumption and the estimate of the wave
energy on studies that explored such a process due to the vigorous core
convection of massive stars just before they experience a core collapse
supernova explosion. Using the stellar evolutionary code MESA we find that the
wave energy causes an expansion within few years by tens to hundreds solar
radii. Despite the large brightening, we expect the increase in radius and
luminosity to substantially enhance mass loss rate and dust formation. The dust
shifts the star to become much redder (to the infrared), and the star might
actually become fainter in the visible. The overall appearance is of a faint
red transient event that lasts for months to few years. We suggest that in some
cases envelope expansion might lead stars that are about to leave the RGB to
engulf exoplanets. The extended envelope has a smaller binding energy to a
degree that allows planets of several Jupiter masses or more and brown dwarfs
to survive the common envelope evolution. We suggest this scenario to account
for the planet orbiting the white dwarf (WD) WD1856+534 (TIC 267574918) and for
the WD - brown dwarf binary system ZTFJ003855.0+203025.5.
