Passive irradiated disk with inner hole

PASSIVE IRRADIATED CIRCUMSTELLAR DISKSWITH AN INNER HOLE

Akinsanmi A. Babatunde

Department of AstronomyUniversity 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

Outline

1 INTRODUCTION

2 MOTIVATION

3 MODEL OF DISK WITH LARGE INNER HOLE

4 COMPUTING THE SED

5 DISCUSSION

6 CONCLUSION

7 REFERENCES


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 fromemissions from proto-planetary/protostellar disk.

The SED of HAeBe also exhibit a NIR or 3µm bump difficult tointerpret with current models.


MOTIVATION

Motivation

How do we model/explain the near-infrared bump observed in theSEDs of Herbig Ae stars?.

Impact of model(s) on the structure of disk.


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...)


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 tobe 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 anoptically thin inner hole.


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 tobe 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 anoptically thin inner hole.


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 inscale height & IR emission.

At large distance, Disk may or may not emerge from the shadow.



Flaring disk



Flaring disk with inner hole



Inner Rim & Flaring disk

Inner disk radius Rrim is determined by requiring that the disktemperature equals the dust evaporation temperature,Tevap = 1500K .

Rrim =(

L∗4πT 4

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.



Shadowed region

shadowed region receives diffused radiation from rim, light scatteredoff halo around disk+star system & diffused radiation from flaringdisk at the far end.


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


COMPUTING THE SED

Structure of example model

inner edge at R = 0.52AU, Rfl = 6.6AU


COMPUTING THE SED

SED of example model


COMPUTING THE SED

Effect of parameters on the SED


COMPUTING THE SED

Model behavior for varying stellar types


COMPUTING THE SED

Applied to T-tauri

This shows the fact that NIR bump is observed in HAeBe and not in TTS.


DISCUSSION

Issues

In upper region of rim, gas drag may not be strong enough to keepdust grains from being blown away by radiation pressure.

Possibility/Stability of the flaring disk at large radius.


DISCUSSION

Observation

Features of SED well reproduced by the model:3µm bump,10µm featureand FIR plateau.


CONCLUSION

conclusion

The passive irradiated disk model with an inner hole has been able toconsistently explain the features (NIR and others) of Herbig Ae starsand extended it to T-Tauri starsRecent determination of mass accretion rate in Herbig Ae/Be starsrevealed values that are sufficiently low to ensure an optically thininner gaseous disk at radii shorter than the dust sublimation radius.Tambovtseva et al. (2001)


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


REFERENCES

...............THANK YOU...............


Documents

Passive irradiated disk with inner hole