Long Baseline Interferometric Observations of the Spatial Distribution of Dust Surrounding Late-Type Stars at 11 microns

Details Long Baseline Interferometric Observations of the Spatial Distribution of Dust Surrounding Late-Type Stars at 11 microns Long Baseline Interferometric Observations of the Spatial Distribution of Dust Surrounding Late-Type Stars at 11 microns

Dec 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992aas...18111405d&link_type=abstract

American Astronomical Society, 181st AAS Meeting, #114.05; Bulletin of the American Astronomical Society, Vol. 24, p.1301

Astronomy and Astrophysics

Astronomy

1

Scientific paper

The spatial distribution of dust around a sample of well-known late-type stars has been studied with the Infrared Spatial Interferometer (ISI) operating at a wavelength 11.15 microns. Radiative transfer modeling of visibility curves obtained by the ISI has yielded estimates of the inner radii of the dust shells, the optical depth at 11 microns, 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 have also been made for those stars not seen in visible light. Roughly 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 (2-5 stellar radii) and at a higher temperature ( ~ 1300 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 (as large as 1 arcsec) and very little dust close to the stars, and includes alpha Ori, alpha Sco, alpha Her, and chi Cyg, This indicates sporadic production of dust and little or no recent dust formation. In addition to the stars mentioned above a still larger study of such stars is underway and visibility curves for some of this larger group will be reported. In some cases a rather advanced radiative transfer model based on the work of Wolfire and Cassinelli (Ap. J. 310, 207, 1986) has been used which self-consistently calculates the temperature distribution and infrared spectrum of the star plus dust shell based on the optical properties of the grains, including grain size distributions and chemistry. For alpha Ori, we have shown that a dust distribution that fits its 11 microns visibility curve very well also produces excellent agreement with its IRAS Low Resolution Spectrum, as well as 8.7 microns and 10.4 microns visibility curves obtained by Dyck and Benson (1992, Astron. J in press).

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