  Recent imaging observations with ALMA and other telescopes found widespread
signatures of planet presence in protoplanetary discs at tens of au separations
from their host stars. Here we point out that the presence of very massive
planets at 0.1 au sized orbits can be deduced for protostars accreting gas at
very high rates, when their discs display powerful Thermal Instability bursts.
Earlier work showed that a massive planet modifies the nature of this
instability, with outbursts triggered at the outer edge of the deep gap opened
by the planet. We present simulations of this effect, finding two types of TI
outbursts: downstream and upstream of the planet, which may or may not be
causally connected. We apply our model to the outburst in Gaia20eae. We find
that the agreement between the data and our disc thermal instability model is
improved if there is a planet of 6 Jupiter masses orbiting the star at 0.062 au
separation. Gaia20eae thus becomes the second episodically erupting star, after
FU Ori, where the presence of a massive planet is strongly suspected. Future
observations of similar systems will constrain the mode and the frequency of
planet formation in such an early epoch.
