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Long Baseline Interferometric Observations of Circumstellar Dust Shells at 11 Microns

Published online by Cambridge University Press:  19 July 2016

W.C. Danchi ,
L. Greenhill ,
M. Bester ,
C.G. Degiacomi ,
C.H. Townes  and
M.G. Wolfire
W.C. Danchi
Affiliation:
Space Sciences Laboratory and Physics Department, University of California at Berkeley, Berkeley, CA 94720 USA
L. Greenhill
Affiliation:
Space Sciences Laboratory and Physics Department, University of California at Berkeley, Berkeley, CA 94720 USA
M. Bester
Affiliation:
Space Sciences Laboratory and Physics Department, University of California at Berkeley, Berkeley, CA 94720 USA
C.G. Degiacomi
Affiliation:
Space Sciences Laboratory and Physics Department, University of California at Berkeley, Berkeley, CA 94720 USA
C.H. Townes
Affiliation:
Space Sciences Laboratory and Physics Department, University of California at Berkeley, Berkeley, CA 94720 USA
M.G. Wolfire
Affiliation:
NASA/Ames Research Center, Space Sciences Division, Moffet Field, CA 94035 USA

Abstract

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The spatial distribution of dust around a sample of well-known late-type stars has been studied with the Infrared Spatial Interferometer (ISI) located at Mt. Wilson. Currently operating with a single baseline as a heterodyne interferometer at 11.15 μm, the ISI has obtained visibility curves of these stars. Radiative transfer modeling of the visibility curves has yielded estimates of the inner radii of the dust shells, the optical depth at 11 μm, and the temperature of the dust at the inner radii. For stars in which the dust is resolved, estimates of the stellar diameter and temperature can also be made. Broadly speaking two classes of stars have been found. One class has inner radii of their dust shells very close to the photospheres of the stars themselves (3–5 stellar radii) and at a higher temperature (~ 1200 K) than previously measured. This class includes VY CMa, NML Tau, IRC +10216, and o Ceti. For the latter two the visibility curves change with the luminosity phase of the star and new dust appears to form at still smaller radii during minimum luminosity. The second class of stars has dust shells with substantially larger inner radii and very little dust close to the stars, and includes α Ori, α Sco, α Her, R Leo, and χ Cyg. This indicates sporadic production of dust and no dust formation within the last several decades.

Keywords

InterferometryDust FormationVariable StarsMass Loss
Type
Imaging Results: Optical and Infrared
Information
Symposium - International Astronomical Union , Volume 158: Very High Angular Resolution Imaging , 1994 , pp. 383 - 386
Copyright
Copyright © Kluwer 1994 

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