TY - JOUR
T1 - Near-infrared IOTA interferometry of the symbiotic star CH Cyg
AU - Hofmann, Karl-Heinz
AU - Beckmann, Udo
AU - Berger, Jean-Philippe
AU - Bloecker, Thomas
AU - Brewer, Michael T.
AU - Lacasse, Marc G.
AU - Malanushenko, Victor
AU - Millan-Gabet, Rafael
AU - Monnier, John D.
AU - Ohnaka, Keiichi
AU - Pedretti, Ettore
AU - Schertl, Dieter
AU - Schloerb, F. Peter
AU - Scholz, Michael
AU - Traub, Wesley A.
AU - Weigelt, Gerd
AU - Yudin, Boris
PY - 2003/2/1
Y1 - 2003/2/1
N2 - 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(¿1)/V(¿2) since ratios of
visibilities of different spectral channels can be measured with higher
precision than absolute visibilities. We found that the 2.03 ¿m
uniform disk diameter of CH Cyg is approximately 1.1 times larger than
the 2.15 ¿m and 2.26 ¿m uniform-disk diameter.
AB - 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(¿1)/V(¿2) since ratios of
visibilities of different spectral channels can be measured with higher
precision than absolute visibilities. We found that the 2.03 ¿m
uniform disk diameter of CH Cyg is approximately 1.1 times larger than
the 2.15 ¿m and 2.26 ¿m uniform-disk diameter.
M3 - Article
VL - 4838
SP - 1043
EP - 1046
JO - Interferometry for Optical Astronomy II
JF - Interferometry for Optical Astronomy II
ER -