Evolved circumstellar disks
Coordinator: Henning Th., Wolf S., Bouwman J.
Abstract:
We propose observations which will test the spectroscopic and imaging capabilities of VISIR. In the given time frame (August 26 - Januar 29), following famous objects with EVOLVED CIRCUMSTELLAR DISKS are well observable:
eps Eri : 03 32 55.84 -09 27 29.7 (alpha_J2000.0, delta_J2000.0)
Selection criteria:
- declination 0
- disks have been confirmed
* spatially well resolved images [no SED]
* confusion with circumstellar shell ruled out
- very well studied (with the exception of AU Mic)
Data:
Program is available and data products can be downloaded
Observations
- Objects : [1] August : eps Eri
- Instrument Mode / Science Goals:
a) Long-slit spectroscopy with the slit parallel to the disk midplane
- low resolution (to account for the possibility to trace the spatial extend of crystalline features)
- wavelength range: 8.0-13.5
SCIENCE GOALS:
- Low resolution spectrum tracing the shape of the features of silicate species @ ~10micron (amorphous, crystalline) and PAHs / Very small grains at a qualitatively new level of spatial and spectral resolution
=> Radial distribution of dust grain processing and growth derived from the Silicate feature
=> Radial distribution of Crystalline grains
=> Radial distribution of PAHs / Very small grains
=> Test of the symmetry of the above radial distribution on "both sides of the star" => Conclusions about short-term processes leading to the modification of the distribution of the medium-sized grain species (e.g., planetesimal collisions = f(r))
b) Imaging @ 10 micron,
Filter : PAH2,
Pixel size: Medium: PFoV 0.127"/Pixel (=> Field of View: 32.5" x 32.5")
SCIENCE GOALS:
- Tracing the distribution of medium-sized dust grains at a qualitatively new level of spatial resolution
=> Radial + Vertical dust density / temperature distribution
=> link to optical / NIR high-resolution observations (@ 10mu the photospheric and dust reemission flux are of the same order of magnitude => simplified star substraction)
=> Radial + Vertical distribution of dust grain growth
=> conclusions about physical state of the disk, including conclusions about the distribution of not directly detectable large bodies
=> Disk structure close to the central star (influence of planets? accelerated dust/disk evolution? stellar radiation? ...)
=> Test of the symmetry of the radial intensity / temperature distribution => Conclusions about short-term processes
General Science Goals:
- Dust evolution in evolved, potentially planet-harbouring circumstellar disks
- Comparison with previous observations of disks in an obviously similar stage of their evolution, but exisiting around different stars (=> e.g. different influence of the stellar radiation field on the reservoir of small dust grains)
- Each of the proposed observations goes clearly beyond the capabilities of other existing instruments. Simultaneously, this allows to address qualitatively new questions related to the late-stage disk evolution (just before they reach the point at which the Solar System is nowadays).
| Name | RA(2000) | DEC(2000) | Mode | Obs.Time (h) | Priority |
| HD 17925 | 02 52 32.1 | -12 46 10.9 | PAH2/0.127 | 1 | 1 |
| 49 Cet | 01 34 37.7 | -15 40 34.8 | PAH2/0.127 | 1 | 2 |
| HD 75505 | 08 41 44.7 | -79 02 53.3 | PAH2/0.127 | 1 | 3 |
| HR 506 | 01 42 29.3 | -53 44 27.0 | PAH2/0.127 | 1 | 4 |
| HR 1082 | 03 31 53.6 | -25 36 50.9 | PAH2/0.127 | 1 | 5 |