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arXiv · 0804.0192

The limb-darkened Arcturus; Imaging with the IOTA/IONIC interferometer

S. Lacour·S. Meimon·E. Thiebaut·G. Perrin·T. Verhoelst·E. Pedretti·P. A. Schuller·L. Mugnier·J. Monnier·J. P. Berger·X. Haubois·A. Poncelet·G. Le Besnerais·K. Eriksson·R. Millan-Gabet·M. Lacasse·W. Traub
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Abstract

This paper is an H band interferometric examination of Arcturus, a star frequently used as a spatial and spectral calibrator. Using the IOTA 3 telescope interferometer, we performed spectro-interferometric observation (R~35) of Arcturus. Atmospheric models and prescriptions were fitted to the data to derive the brightness distribution of the photosphere. Image reconstruction was also obtained using two software algorithms: Wisard and Mira. An achromatic power law proved to be a good model of the brightness distribution, with a limb darkening compatible with the one derived from atmospheric model simulations using our Marcs model. A Rosseland diameter of 21.05+/-0.21 was derived, corresponding to an effective temperature of T_eff=4295+/-26 K. No companion was detected from the closure phases, with an upper limit on the brightness ratio of 8e-4 at 1AU. Dynamic range at such distance from the photosphere was established at 1.5e-4 (1sigma rms). An upper limit of 1.7e-3 was also derived for the level of brightness asymmetries present on the photosphere.

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S. Lacour, S. Meimon, E. Thiebaut, G. Perrin, T. Verhoelst, E. Pedretti, P. A. Schuller, L. Mugnier, J. Monnier, J. P. Berger, X. Haubois, A. Poncelet, G. Le Besnerais, K. Eriksson, R. Millan-Gabet, M. Lacasse, W. Traub. 2008-04-01. The limb-darkened Arcturus; Imaging with the IOTA/IONIC interferometer. https://doi.org/10.1051/0004-6361:200809611

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