20 October 2004 High-resolution near-infrared speckle interferometry and radiative transfer modeling of the OH/IR star OH 104.9+2.4
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Abstract
We present near-infrared speckle interferometry of the OH/IR star OH 104.9+2.4 in the $K'$ band obtained with the 6m telescope of the Special Astrophysical Observatory (SAO). At a wavelength of λ = 2.12 micron the diffraction-limited resolution of 74 mas was attained. The reconstructed visibility reveals a spherically symmetric, circumstellar dust shell (CDS) surrounding the central star. The visibility function shows that the stellar contribution to the total flux at λ = 2.12 micron is less than ~50%, indicating a rather large optical depth of the CDS. The azimuthally averaged 1-dimensional Gaussian visibility fit yields a diameter of 47 +/- 3 mas (FHWM), which corresponds to 112 +/- 13 AU for an adopted distance of D = 2.38 +\- 0.24 kpc. To determine the structure and the properties of the CDS of OH 104.9+2.4, radiative transfer calculations using the code DUSTY were performed to simultaneously model its visibility and the spectral energy distribution (SED). We found that both the ISO spectrum and the visibility of OH 104.9+2.4 can be well reproduced by a radiative transfer model with an effective temperature Teff = 2500 +/- 500 K of the central source, a dust temperature Tin = 1000 +/- 200 K at the inner shell boundary Rin = 9.1 Rstar = 25.4 AU, an optical depth tau = 6.5 +/- 0.3 at 2.2 micron, and dust grain radii ranging from amin = 0.005 +/- 0.003 micron to amax = 0.2 +/- 0.02 micron with a power law with index -3.5. It was found that even minor changes in amax have a major impact on both the slope and the curvature of the visibility function, while the SED shows only minor changes. Our detailed analysis demonstrates the potential of dust shell modeling constrained by both the SED and visibilities.
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Dominik Riechers, Yuri Y. Balega, Thomas M. Driebe, Karl-Heinz Hofmann, Alexander B. Men'shchikov, Dieter Schertl, Gerd P. Weigelt, "High-resolution near-infrared speckle interferometry and radiative transfer modeling of the OH/IR star OH 104.9+2.4", Proc. SPIE 5491, New Frontiers in Stellar Interferometry, (20 October 2004); doi: 10.1117/12.551413; https://doi.org/10.1117/12.551413
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