Extreme evaporation of planets in hot thermally unstable protoplanetary discs: the case of FU Ori
Disc accretion rate onto low mass protostar FU Ori suddenly increased hundreds of times 85 yr ago and remains elevated to this day. We show that the sum of historic and recent observations challenges existing FU Ori models. We build a theory of a new process, Extreme Evaporation (EE) of young gas giant planets in discs with midplane temperatures of ≳ 30 000 K. Such temperatures are reached in the inner 0.1 AU during thermal instability bursts. In our 1D time-dependent code the disc and an embedded planet interact through gravity, heat, and mass exchange. We use disc viscosity constrained by simulations and observations of dwarf novae instabilities, and we constrain planet properties with a stellar evolution code. We show that dusty gas giants born in the outer self-gravitating disc reach the innermost disc in a ∼O(104) yr with radius of ∼10RJ. We show that their EE rates are $\gtrsim 10^{-5} {\rm {\rm M}_{\odot }}$ yr−1; if this exceeds the background disc accretion activity then the system enters a planet-sourced mode. Like a stellar secondary in mass-transferring binaries, the planet becomes the dominant source of matter for the star, albeit for ∼O(100) yr. We find that a ∼6 Jupiter mass planet evaporating in a disc fed at a time-averaged rate of $\sim 10^{-6} {\rm {\rm M}_{\odot }}$ yr−1 appears to explain all that we currently know about FU Ori accretion outburst. More massive planets and/or planets in older less massive discs do not experience EE process. Future FUOR modelling may constrain planet internal structure and evolution of the earliest discs.
Funding
Astrophysics Research at the University of Leicester
Science and Technology Facilities Council
Find out more...Royal Society University Research Fellowship
European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 853022, PEVAP)
This research used the ALICE High Performance Computing Facility at the University of Leicester, and DiRAC Data Intensive service at Leicester, operated by the University of Leicester IT Services, which forms part of the STFC DiRAC HPC Facility (www.dirac.ac.uk)
History
Author affiliation
College of Science & Engineering/Physics & AstronomyVersion
- VoR (Version of Record)
Published in
Monthly Notices of the Royal Astronomical SocietyVolume
523Issue
1Pagination
385 - 403Publisher
Oxford University Press (OUP)issn
0035-8711eissn
1365-2966Copyright date
2023Available date
2024-03-14Publisher DOI
Language
enPublisher version
Deposited by
Professor Sergei NayakshinDeposit date
2024-03-13Data Access Statement
The data obtained in our simulations can be made available on reasonable request to the corresponding author.Rights Retention Statement
- Yes