Powered by Indico
v3.2.3
The brightness of the prototypical low mass protostar FU Ori suddenly increased to hundreds of Solar luminosities some 85 years ago and remains elevated to this day. While disc accretion onto the star is the undisputed origin of the outburst, several competing disc models exist. Recent interferometric observations (Lykou +22) reveal that the size of the actively accreting disc is only 0.3 AU. Photometric variability suggests a hot spot in the disc orbiting the star at the distance of about 0.08 AU. Here we show that both of these facts are naturally explained if material that feeds FU Ori outburst originates in a giant planet orbiting the star at 0.08 AU. We show that discs at this location have mid-plane temperatures up to ∼ 30, 000 K during well known Hydrogen ionisation (thermal instability, Bell & Lin 1994) bursts. Young gas giant planets embedded in such discs are susceptible to thermal opacity-limited extreme evaporation (EE). We build an analytical theory of the process, verify it numerically, and incorporate it into a time-dependent code of a disc with an embedded planet. We find that steady-state FUOR-like outbursts are ignited when moderately massive planets migrating in very young discs reach distances ∼ 0.1 AU from the star where thermal instability operates. Their Extreme Evaporation then injects the matter in the surrounding discs at rates exceeding 10^-5 Msun/yr, so that the planet becomes the main source of matter for the innermost disc. The planet is thus a miniature secondary star losing mass via thermally driven wind (not Roche lobe overflow as previous authors, including ourselves, believed). Our theory place significant constraints on the the structure of discs that can yield EE-fed bursts: these may only occur in discs with accretion rate exceeding a few 10^-7 Msun/yr, and likely not older than 0.1 Myr. Similarly, only planets born by gravitational instability, and having accreted significant amounts of dust/pebbles from the disc, may participate in this process. We are therefore able to place interesting constraints on large scale disc viscosity of very young massive discs, and the speed with which these youngest systems evolve.
1993 MSc in Theoretical Physics, Moscow Engineer Physics Institute
1998 PhD, University of Arizona, Tucson
1998-2001 NRC Fellow, NASA Goddard Space Flight Center
2001-2005 Postdoc, Max Plank Astrophysics Institute, Garching
From 2005: Professor, University of Leicester
He has travelled around quite a bit and has been working on Gravitationally unstable discs in various context (mainly the supermassive blackhole in the centre of Milky Way and protoplanetary discs).
Place: N630
Join Tencent Meeting
https://meeting.tencent.com/dm/JEkp5TGowcVu
Meeting ID: 705-350-411