The youngest of hot jupiters in action: episodic accretion outbursts in Gaia20eae

TL;DR

This paper models how massive planets in close orbits can trigger thermal instability outbursts in protoplanetary discs, explaining the episodic eruption observed in Gaia20eae and suggesting early planet formation.

Contribution

It introduces a simulation of thermal instability bursts influenced by massive planets, applied to Gaia20eae, indicating early planet formation at 0.062 au.

Findings

Two types of thermal instability outbursts identified

A 6 Jupiter mass planet explains Gaia20eae's outburst

Supports early formation of massive planets in protoplanetary discs

Abstract

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.