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Proceedings Paper

Near-infrared IOTA interferometry of the symbiotic star CH Cyg
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Paper Abstract

We present observations of the symbiotic star CH Cyg with a new JHK-band beam combiner mounted to the IOTA interferometer. The new beam combiner consists of an anamorphic cylindrical lens system and a grism, and allows the simultaneous recording of spectrally dispersed J-, H- and K-band Michelson interferograms. The observations of CH Cyg were conducted on 5, 6, 8 and 11 June 2001 using baselines of 17m to 25m. From the interferograms of CH Cyg, J-, H-, and K-band visibility functions can be determined. Uniform-disk fits to the visibilities give, e.g., stellar diameters of (7.8 ± 0.6) mas and (8.7 ± 0.8) mas in H and K, respectively. Angular stellar filter radii and Rosseland radii are derived from the measured visibilities by fitting theoretical center-to-limb intensity variations (CLVs) of Mira star models. The available HIPPARCOS parallax of CH Cyg allows us to determine linear radii. For example, on the basis of the K-band visibility, Rosseland radii in the range of 214 to 243 solar radii can be derived utilizing CLVs of different fundamental mode Mira models as fit functions. These radii agree well within the error bars with the corresponding theoretical model Rosseland radii of 230 to 282 solar radii. Models of first overtone pulsators are not in good agreement with the observations. The wavelength dependence of the stellar diameter can be well studied by using visibility ratios V(λ1)/V(λ2) since ratios of visibilities of different spectral channels can be measured with higher precision than absolute visibilities. We found that the 2.03 μm uniform disk diameter of CH Cyg is approximately 1.1 times larger than the 2.15 μm and 2.26 μm uniform-disk diameter.

Paper Details

Date Published: 21 February 2003
PDF: 4 pages
Proc. SPIE 4838, Interferometry for Optical Astronomy II, (21 February 2003); doi: 10.1117/12.458904
Show Author Affiliations
Karl-Heinz Hofmann, Max-Planck-Institut fuer Radioastronomie (Germany)
Udo Beckmann, Max-Planck-Institut fuer Radioastronomie (Germany)
Jean-Philippe Berger, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Thomas Bloecker, Max-Planck-Institut fuer Radioastronomie (Germany)
Michael T. Brewer, Univ. of Massachusetts/Amherst (United States)
Marc G. Lacasse, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Victor Malanushenko, Crimean Astrophysical Observatory (Ukraine)
Rafael Millan-Gabet, Harvard-Smithsonian Ctr. for Astrophysics (United States)
John D. Monnier, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Keiichi Ohnaka, Max-Planck-Institut fuer Radioastronomie (Germany)
Ettore Pedretti, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Dieter Schertl, Max-Planck-Institut fuer Radioastronomie (Germany)
F. Peter Schloerb, Univ. of Massachusetts/Amherst (United States)
Michael Scholz, Univ. of Heidelberg (Germany)
Wesley A. Traub, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Gerd Weigelt, Max-Planck-Institut fuer Radioastronomie (Germany)
Boris Yudin, Sternberg Astronomical Institute (Russia)


Published in SPIE Proceedings Vol. 4838:
Interferometry for Optical Astronomy II
Wesley A. Traub, Editor(s)

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