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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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$\approx$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$\pm$0.21 was derived, corresponding to an effective temperature of $T_{\rm
eff}$ = 4295$\pm$26 K. No companion was detected from the closure phases, with an upper limit on the brightness ratio of 8$\times$10-4 at 1 AU. The dynamic range at such distance from the photosphere was established as 1.5$\times$10-4 (1$\sigma\,$rms). An upper limit of 1.7$\times$10-3 was also derived for the level of brightness asymmetries present in the photosphere.
Original languageUndefined/Unknown
Pages (from-to)561-570
Number of pages10
JournalAstronomy and Astrophysics
Issue number2
Publication statusPublished - 22 Apr 2008


  • techniques: interferometric, stars: fundamental parameters, infrared: stars, stars: individual: Arcturus

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