1. PASSIVE IRRADIATED CIRCUMSTELLAR DISKS
WITH AN INNER HOLE
Akinsanmi A. Babatunde
Department of Astronomy
University of Porto
Paper by Dullemond et al (2001)
AST 4004, June 2016
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 1 / 22

2. Outline
1 INTRODUCTION
2 MOTIVATION
3 MODEL OF DISK WITH LARGE INNER HOLE
4 COMPUTING THE SED
5 DISCUSSION
6 CONCLUSION
7 REFERENCES
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 2 / 22

3. INTRODUCTION
Introduction
Herbig Ae/Be (HAeBe) stars are intermediate mass pre-MS stars.
Like C-TTS they can have strong IR-excess thought to be from
emissions from proto-planetary/protostellar disk.
The SED of HAeBe also exhibit a NIR or 3µm bump difficult to
interpret with current models.
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 3 / 22

4. MOTIVATION
Motivation
How do we model/explain the near-infrared bump observed in the
SEDs of Herbig Ae stars?.
Impact of model(s) on the structure of disk.
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 4 / 22

5. MOTIVATION
Disk Models
Disks powered by accretion(Lin et al 1980; Bell & Lin 1994)
Irradiated non-accreting (passive) disks. (Kenyon & Hartmann 1987;Chiang & Goldreich
1997 [CG97])
Irradiated accretion disks. (Ruden & Pollack 1991...)
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 5 / 22

6. MOTIVATION
Disk Models
Hillenbrand et al. fitted well SED of HAe/Be with an optically thick,
geometrically flat accretion disk (but inner part of the radius had to
be optically thin to explain NIR bump)
But an inner thin disk was not consistent with the large accretion rate.
Natta et al. proposed instead a model of passive flared disk
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 6 / 22

7. MOTIVATION
Disk Models
Hillenbrand et al. fitted well SED of HAe/Be with an optically thick,
geometrically flat accretion disk (but inner part of the radius had to
be optically thin to explain NIR bump)
But an inner thin disk was not consistent with the large accretion rate.
Natta et al. proposed instead a model of passive flared disk with an
optically thin inner hole.
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 6 / 22

8. MODEL OF DISK WITH LARGE INNER HOLE
Disk with larger inner hole
Truncate flaring disk at specific radius (dust evaporation radius)
which creates an inner hotter & puffed up rim.
Emission from inner rim produces an NIR bump similar to observed.
Inner rim will cast a shadow over disk behind it causing decrease in
scale height & IR emission.
At large distance, Disk may or may not emerge from the shadow.
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 7 / 22

9. MODEL OF DISK WITH LARGE INNER HOLE
Flaring disk
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 8 / 22

10. MODEL OF DISK WITH LARGE INNER HOLE
Flaring disk with inner hole
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 9 / 22

11. MODEL OF DISK WITH LARGE INNER HOLE
Inner Rim & Flaring disk
Inner disk radius Rrim is determined by requiring that the disk
temperature equals the dust evaporation temperature,
Tevap = 1500K.
Rrim = L∗
4πT4
rim
1/2
1 + Hrim
Rrim
1/2
.
The Flaring disk absorbs flux F∗
irr half of which is radiated away from
disk and the other half into deeper layers.
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 10 / 22

12. MODEL OF DISK WITH LARGE INNER HOLE
Shadowed region
shadowed region receives diffused radiation from rim, light scattered
off halo around disk+star system & diffused radiation from flaring
disk at the far end.
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 11 / 22

13. COMPUTING THE SED
Example Model
Model with star with Teff = 9500K, L∗ = 47L , M∗ = 2.4M .
Disk with Rout = 400AU, inner radius at dust condensation point
(Trim = 1500k) i.e. Rrim = 0.47AU seen at i = 45o
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 12 / 22

14. COMPUTING THE SED
Structure of example model
inner edge at R = 0.52AU, Rfl = 6.6AU
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 13 / 22

15. COMPUTING THE SED
SED of example model
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 14 / 22

16. COMPUTING THE SED
Effect of parameters on the SED
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 15 / 22

17. COMPUTING THE SED
Model behavior for varying stellar types
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 16 / 22

18. COMPUTING THE SED
Applied to T-tauri
This shows the fact that NIR bump is observed in HAeBe and not in TTS.
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 17 / 22

19. DISCUSSION
Issues
In upper region of rim, gas drag may not be strong enough to keep
dust grains from being blown away by radiation pressure.
Possibility/Stability of the flaring disk at large radius.
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 18 / 22

20. DISCUSSION
Observation
Features of SED well reproduced by the model:3µm bump,10µm feature
and FIR plateau.
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 19 / 22

21. CONCLUSION
conclusion
The passive irradiated disk model with an inner hole has been able to
consistently explain the features (NIR and others) of Herbig Ae stars
and extended it to T-Tauri stars
Recent determination of mass accretion rate in Herbig Ae/Be stars
revealed values that are sufficiently low to ensure an optically thin
inner gaseous disk at radii shorter than the dust sublimation radius.
Tambovtseva et al. (2001)
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 20 / 22

22. REFERENCES
Reference
Chiang, E. I., & Goldreich, P. 1997, ApJ, 490, 368
Hartmann, L., Kenyon, S. J., & Calvet, N. 1993, ApJ, 407, 219
Hillenbrand, L. A., Strom, S. E., Vrba, F. J., & Keene, J. 1992, ApJ.
Lin, D. N. C., & Papaloizou, J. 1980, MNRAS, 191, 37
Natta, A., Prusti, T., Neri, R., Grinin, V. P., & Mannings, V. 2001
Ruden, S. P., & Pollack, J. B. 1991, ApJ, 375, 740
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 21 / 22

23. REFERENCES
...............THANK YOU...............
Akinsanmi A. Babatunde (University of Porto)PASSIVE IRRADIATED CIRCUMSTELLAR DISKS WITH AN INNER HOLEAST 4004, June 2016 22 / 22