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| Paper: |
IR Imaging of Circumstellar Environments |
| Volume: |
154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop |
| Page: |
361 |
| Authors: |
Danchi, W. C.; Tuthill, P. G.; Bester, M.; Lipman, E. A.; Monnier, J. M.; Townes, C. H. |
| Abstract: |
Long baseline interferometry at mid-infrared (8-12 micron) and near-infrared (J,H,K,L) bands is providing a new observational perspective on the environment within a few stellar radii of the photospheres of late-type stars. Results will be presented primarily from recent work with the University of California, Berkeley, Infrared Spatial Interferometer, a two-telescope stellar interferometer, having a variable baseline. Interferometry in the mid-infrared is particularly suited to examining the distribution of dust clouds emitted by late-type stars, and also stellar diameters, since the effects of limb-darkening and stellar hot spots are small. Results show the location of initial dust formation, the distribution of emitted material, and in some cases its motion, the average rates of emission of material, and the relation between circumstellar clouds and masers. Of the sample of 15 stars studied thus far, a substantial fraction has major dust emission episodes separated by 10--100 years; others emit continuously or on each luminosity cycle. Stars which have been studied in some detail include IRC +10216, alpha Ori, o Cet, NML Cyg, and NML Tau (IK Tau). Related observations using non-redundant aperture masking techniques have been performed at the Keck I telescope in the near-infrared. Preliminary results at 2.2 microns and 3.1 microns have been obtained on the morphology of the hot dust at the inner radius of the dust formation zone. In some cases (IRC +10216 and VY CMa) a complex morphology has been found. In other cases (NML Tau and NML Cyg) the morphology is more circularly symmetric. Details of our Keck I observations, including preliminary results on stellar diameters at J, H, K, and L, will be presented in the poster paper by Tuthill et al. also at this conference. |
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