21 February 2003 Near-infrared IOTA interferometry of the symbiotic star CH Cyg
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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.
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Karl-Heinz Hofmann, Karl-Heinz Hofmann, Udo Beckmann, Udo Beckmann, Jean-Philippe Berger, Jean-Philippe Berger, Thomas Bloecker, Thomas Bloecker, Michael T. Brewer, Michael T. Brewer, Marc G. Lacasse, Marc G. Lacasse, Victor Malanushenko, Victor Malanushenko, Rafael Millan-Gabet, Rafael Millan-Gabet, John D. Monnier, John D. Monnier, Keiichi Ohnaka, Keiichi Ohnaka, Ettore Pedretti, Ettore Pedretti, Dieter Schertl, Dieter Schertl, F. Peter Schloerb, F. Peter Schloerb, Michael Scholz, Michael Scholz, Wesley A. Traub, Wesley A. Traub, Gerd Weigelt, Gerd Weigelt, Boris Yudin, Boris Yudin, } "Near-infrared IOTA interferometry of the symbiotic star CH Cyg", Proc. SPIE 4838, Interferometry for Optical Astronomy II, (21 February 2003); doi: 10.1117/12.458904; https://doi.org/10.1117/12.458904
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