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Time-Dependent Phenomena in Protoplanetary Disks

Time-Dependent Phenomena in Protoplanetary Disks. Zhaohuan Zhu. Advisor: Lee Hartmann. Collaborators: Charles Gammie(UIUC), Nuria Calvet (Umich), Catherine Espaillat(CFA), Richard Durisen, Kai Cai, Jesus Hernandez. Introduction. “Luminosity Problem” (Kenyon et al. 1990)

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Time-Dependent Phenomena in Protoplanetary Disks

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  1. Time-Dependent Phenomena in Protoplanetary Disks Zhaohuan Zhu Advisor: Lee Hartmann Collaborators: Charles Gammie(UIUC), Nuria Calvet (Umich), Catherine Espaillat(CFA), Richard Durisen, Kai Cai, Jesus Hernandez

  2. Introduction • “Luminosity Problem”(Kenyon et al. 1990) • Ṁ~Mʘ /105 yrs~10-5 Mʘ yr-1 L~ ~20 Lʘfor 0.3 Mʘ,2 Rʘ • Observed L peaks at <0.5 Lʘ • Solution: Infall to disk, with episodic disk accretion (Evans et al 2008) Ṁinfall~10-5 Mʘ yr-1 Ṁinfall~10-5 Mʘ yr-1 quiescent outburst Ṁ~10-8 Mʘ yr-1 Ṁ~10-4 Mʘ yr-1

  3. Accretion disk model predicts SED, variation of spectral type and rotation with wavelength. FU Ori : example of episodic accretion (Zhu et al 2007, 2008) 2000 K 6000 K 0.5-1 AU Accrete 10-2 Mʘ in 100 year Massive inner disk α~0.02-0.2

  4. Outburst mechanism: general picture GI (Armitage et al. 2001, Zhu, Hartmann, Gammie 2009 a,b)

  5. Outburst mechanism: 2 D simulations • ZEUS axisymmetric hydro-simulation of viscous fluid accretion • With the artificial viscosity of MRI and GI and the radiative cooling • Movie1 (Zhu et al. 2009b) 4 stages

  6. Outburst mechanism: 2 D simulations • Compared with Observation • Maximum mass accretion rate • Outburst duration time • High Ṁ disk size • Short time scale variations

  7. Disk long term evolution: layered picture Faster rotating core • Longterm 1-D 2-Zone model with infall to disk MRI Dead Zone MRI GI (1) (2) (3) (2) Fiducial model (1) Slower rotating core (3) Ease Luminosity problem Initial core rotation important (Zhu et al. submitted)

  8. Disk long term evolution: Predictions Compare with current observation and Predict with future obeservations W =10-14 W=2 X10-14 ad=0.001 viscous W =10-14 W=3 X10-15 Massive dead zone within 10 AU

  9. Conclusion: • Pure TI model does not work for FU Ori outbursts • GI+MRI model does work • It can explain the Luminosity problem • The disk may have a massive ‘dead zone’ which can be observed by future EVLA, ALMA observations • Ongoing work Azimuthal 2D to treat self-gravity consistently How do planets open a hole or gap in accreting disks, which can be compared with (Pre)Transitional disks.

  10. (Evans et al. 2008)

  11. FU Orionis objects: disk differential rotation optical 2µm 5 µm Zhu et al. 2009 b • Support the disk accretion model • The high Ṁ disk could extend to • 0.5 AU (Close to Keplarian rotation velocity at 0.5 AU)

  12. FU Orionis objects: flared outer disk or envelope? V1515 Cyg • BBW 76 & V1515 Cyg BBW 76 (Zhu et al. 2008 ) The variety of dusty structures (flared disks for FU Ori and BBW 76; an envelope for V1515 Cyg) suggests that FU Orionis phase can be present at either early or late stages of protostellar evolution.

  13. (Pre-)Transitional disk Constant nu Constant alpha

  14. TI and S curve Cooling>heating heating>cooling Tc unstable Stable Σ

  15. Opacity With , if the disk is convectively unstable.

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