The limb-darkened Arcturus: imaging with the IOTA/IONIC interferometer

S. Lacour, S. Meimon, E. Thiébaut, 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, S. Ragland, M. Lacasse, W. Traub

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Abstract

Aims: We undertook an H band interferometric examination of Arcturus, a star frequently used as a spatial and spectral calibrator. Methods: Using the IOTA 3 telescope interferometer, we performed spectro-interferometric observations (R¿35) of Arcturus. Atmospheric models and prescriptions were fitted to the data to derive the brightness distribution of the photosphere. Image reconstruction was performed using two software algorithms: Wisard and Mira. Results: 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 Teff = 4295±26 K. No companion was detected from the closure phases, with an upper limit on the brightness ratio of 8×10-4 at 1 AU. The dynamic range at such distance from the photosphere was established as1.5×10-4 (1¿ rms). An upper limit of1.7×10-3 was also derived for the level of brightness asymmetries present in the photosphere.
Original languageEnglish
Pages (from-to)561-570
JournalAstronomy & Astrophysics
Volume485
Issue number2
Publication statusPublished - 1 Jul 2008

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Lacour, S., Meimon, S., Thiébaut, E., Perrin, G., Verhoelst, T., Pedretti, E., ... Traub, W. (2008). The limb-darkened Arcturus: imaging with the IOTA/IONIC interferometer. Astronomy & Astrophysics, 485(2), 561-570.