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Massive planets in FU Orionis objects

Massive planets in FU Orionis objects. Giuseppe Lodato Institute of Astronomy, Cambridge. In collaboration with Cathie Clarke (IoA). Rise timescale: t rise ≈ 1 yr (FU Ori and V1057 Cyg) t rise ≈ 20 yr (V1515 Cyg). Decay timescale: t decay ≈ 10 yr (V1057 Cyg)

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Massive planets in FU Orionis objects

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  1. Massive planets in FU Orionis objects Giuseppe Lodato Institute of Astronomy, Cambridge In collaboration with Cathie Clarke (IoA)

  2. Rise timescale: trise≈ 1 yr (FU Ori and V1057 Cyg) trise ≈ 20 yr (V1515 Cyg) Decay timescale: tdecay≈ 10 yr (V1057 Cyg) tdecay ≈ 50-100 yr (FU Ori and V1515 Cyg) FU Orionis objects • Large outbursts: DL≈ 2-3 orders fo magnitude • Sudden increase in the mass accretion rate in the circumstellar disc • Accretion disc SED fit the observation for l<10mmKenyon & Hartmann 1991 • Double peaked optical - near IR line profiles

  3. Outburst mechanism • Tidal interaction with a companion star Bonnel & Bastien 1992 • Gravitational instability in a massive disc Armitage, Livio & Pringle 2001 • Thermal instability Clarke, Lin & Papaloizou 1989 Bell & Lin 1994, Bell et al 1995

  4. Unstable branch Stable branches Limit cycle instability Outwardly propagating front: slow Inwardly propagating front: fast m=nS

  5. Time-scale problem for thermal instability models • Bell & Lin (1994): accurate vertical structure calculations • SA and SB are strongly increasing function of R: instability triggered close to the inner edge • Slow rise timescale: trise≈ 10 yr • A fast rise time would be achieved if Rtrig ≈ 10 Ro

  6. Clarke & Armitage 2003 Herbig et al. 2003 A massive planet in FU Orionis discs • Periodic modulation of the line profiles: the signature of a massive planet? (Clarke & Armitage 2003) • Accretion onto the embedded planet • Hot spot in the disc at the instantaneous position of the planet • Observational evidence (Herbig et al. 2003)

  7. Influence of the planet on the outburst • Gap formation: rapid draining of the inner disc • Planet migration (Type II) : if the planet is massive enough, it is slower than the viscous evolution • Banking up of S upstream of the planet position • Triggered instability at planet position Rs Clarke & Syer 1996

  8. . m=nS=M/3p meq define the S-curve: analytical approximation from the Bell & Lin (1994) results Coupled planet-disc evolutionThe disc

  9. Analytic prediction from Ivanov et al. 1999 Coupled planet-disc evolution Planet migration Banking up

  10. Planet induced outbursts: the "reference" case . Min = 3 10-6 Mo/yr Ms = 15 MJupiter

  11. Details of the planet induced outburst • Trigger radius: Rtrig≈ 11 Ro • Mass accretion rate in the inner disc during the outburst: Mout≈ 2.1 10-4 Mo/yr • Peak luminosity ≈ 400 Lo • Outer propagation radius of the instability Rlim ≈ 50 Ro .

  12. Rise time: trise≈ 2yr Peak luminosity: 400 Lo Light curves

  13. Long term evolution • Radial migration of the planet significantly slowed down. • Residual migration causes Rtrig to decrease • Most outburst features determined by Rtrig • Subsequent outbursts have: • Smaller amplitude (by a factor 2, after 10 outbursts) • Shorter recurrence time (by a factor 3, after 10 outbursts) • Longer rise time

  14. Dependence on planet mass • As planet mass increases, outbursts are triggered at progressively larger radii

  15. Summary of results • Massive planet (with M ≈ 10-15 MJupiter) able to trigger FU Orionis outbursts at R≈ 10 Ro • Outbursts properties (amplitude, duration, rise time) depend on the location where the outburst is triggered • Fast rise time (1-2 yr) if Ms ≈ 10-15 MJupiter • Radial migration of the planet significantly slowed down by the occurence of the outbursts

  16. Remaining issues and fututre developments • Steadiness of FU Orionis: tdecay< 60-70 yr in our models. All thermal instability models suffer from this problem. • What happens to the planet during the outburst? Both dynamically and physically • Long term evolution and planet migration • Triggered outburst for lower feeding rates?

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