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) Solution:
Ṁ~Mʘ /105 yrs~10-5 Mʘ yr-1
L~ ~20 Lʘ for 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. FU Ori : example of episodic accretion
Accretion disk model predicts SED, variation of spectral type and rotation with wavelength.
(Zhu et al 2007, 2008)
2000 K
6000 K
0.5-1 AU α~
Accrete 10-2 Mʘ in 100 year Massive inner disk

4. Outburst mechanism: general pictureGI
(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
Longterm 1-D 2-Zone model with infall to disk
Faster rotating core
MRI
MRI GI
Dead
Zone
(1)
(2)
(3)
(2)
(1)
Fiducial model
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: Ongoing work Azimuthal 2D to treat
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)

12. FU Orionis objects: disk differential rotation
optical
2µm
5 µm
Zhu et al 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)

13. FU Orionis objects: flared outer disk or envelope?
BBW 76 & V1515 Cyg
V1515 Cyg
BBW 76
(Zhu et al )
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.

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

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

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