Is Arcturus a well-understood K giant?. Test of model atmospheres and potential companion detection by near-infrared interferometry

Tijl Verhoelst (1, 2, 3) , P. Bordé (4) , Guy Perrin (2, 3) , Leen Decin (1) , K. Eriksson (5) , Stephen Ridgway (2, 3, 6) , Peter A. Schuller (4) , Wesley A. Traub (4) , Rafael Millan-Gabet (6) , M. G. Lacasse (4) , Christoffel Waelkens (1)

1 Instituut voor Sterrenkunde, Katholieke Universiteit Leuven
2 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
3 Pôle Astronomie du LESIA
4 Harvard-Smithsonian Center for Astrophysics
5 Institute for Astronomy and Space Physics
6 NOAO - National Optical Astronomy Observatory, Tucson

We present near-IR interferometric measurements of the K1.5 giant Arcturus (alpha Bootis), obtained at the IOTA interferometer with the FLUOR instrument, in four narrow filters with central wavelengths ranging from 2.03 mum to 2.39 mum. These observations were expected to allow us to quantify the wavelength dependence of the diameter of a typical K giant. They are compared to predictions from both plane-parallel and spherical model atmospheres. Unexpectedly, neither can explain the observed visibilities. We show that these data suggest the presence of a companion, in accordance with the Hipparcos data on this star, and discuss this solution with respect to Arcturus' single star status.

Domaines: Astrophysique [astro-ph]

Tijl Verhoelst, P. Bordé, Guy Perrin, Leen Decin, K. Eriksson, et al.. Is Arcturus a well-understood K giant?. Test of model atmospheres and potential companion detection by near-infrared interferometry. Astronomy and Astrophysics - A&A, 2005, 435, pp.289-301. ⟨10.1051/0004-6361:20042356⟩. ⟨hal-03786638⟩