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Extreme evaporation of planets in hot thermally unstable protoplanetary discs: the case of FU Ori

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posted on 2024-03-14, 11:28 authored by Sergei Nayakshin, James E Owen, Vardan Elbakyan

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

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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 & Astronomy

Version

  • VoR (Version of Record)

Published in

Monthly Notices of the Royal Astronomical Society

Volume

523

Issue

1

Pagination

385 - 403

Publisher

Oxford University Press (OUP)

issn

0035-8711

eissn

1365-2966

Copyright date

2023

Available date

2024-03-14

Language

en

Deposited by

Professor Sergei Nayakshin

Deposit date

2024-03-13

Data Access Statement

The data obtained in our simulations can be made available on reasonable request to the corresponding author.

Rights Retention Statement

  • Yes

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