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Astron. Astrophys. 363, 984-990 (2000)
Occultation of young stellar objects by circumstellar disks
I. Theoretical expectations and preliminary comparison with observations
C. Bertout
Institut d'Astrophysique, 98bis Boulevard Arago, 75014 Paris, France (bertout@iap.fr)
Received 3 May 2000 / Accepted 7 September 2000
Abstract
The hypothesis that partial occultation of young stars by their
circumstellar disks is responsible for UX Ori and T Tauri
Type III photometric variability is quantitatively studied. We
construct accretion disk models in which reprocessing of stellar and
accretion luminosity leads to flaring of the disk (assumed to be in
vertical hydrostatic equilibrium), and compute the probability to
observe the star through the disk atmosphere. The mass accretion rate
is found to primarily determine the range of view angles over which
the star is fully or partially obscured by the disk. For average
disk/star parameters relevant to active T Tauri stars, the
probability of observing occultation events is
![[FORMULA]](img1.gif)
0.15, while it is typically 0.2 for
parameters relevant to UX Ori. A preliminary analysis of available
photometric data confirms these estimates and allows us to uncover in
some stars cyclic variability on a time-scale of weeks to years that
may tentatively be attributed to disk inhomogeneities or warps. These
results suggest that direct observational study of the disk structure
may be possible for a sizable fraction of young stellar objects.
Key words: accretion, accretion
disks 
stars:
formation
stars: pre-main
sequence
stars: variables: general
Contents
- 1. Introduction
- 2. The probability of observing YSO occultation
- 2.1. Disk model
- 2.2. Results
- 3. Discussion and preliminary comparison with observations
- Acknowledgements
- References
© European Southern Observatory (ESO) 2000
Online publication: December 5, 2000
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