The K-band intensity profile of R Leonis probed by VLTI/VINCI ^*

¹ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany e-mail: mwittkow@eso.org
² Dipartimento di Astronomia, Università di Padova, Vicolo dell'Osservatorio 2, 35122 Padova, Italy
³ Institut für Theoretische Astrophysik der Universität Heidelberg, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany
⁴ School of Physics, University of Sydney, NSW 2006, Australia
⁵ Research School for Astronomy and Astrophysics, Australian National University, Canberra, ACT 2600, Australia

Received: 15 September 2004
Accepted: 19 October 2004

Abstract

We present near-infrared K-band interferometric measurements of the Mira star R Leonis obtained in April 2001 and January 2002 with the VLTI, the commissioning instrument VINCI, and the two test siderostats. These epochs correspond to near-maximum stellar variability phases ~0.08 and ~1.02 (one cycle later), respectively. The April 2001 data cover a range of spatial frequencies (31–35 cycles/arcsecond) within the first lobe of the visibility function. These measurements indicate a center-to-limb intensity variation (CLV) that is clearly different from a uniform disk (UD) intensity profile. We show that these measured visibility values are consistent with predictions from recent self-excited dynamic Mira model atmospheres that include molecular shells close to continuum-forming layers. We derive high-precision Rosseland diameters of  mas and  mas for the April 2001 and January 2002 data, respectively. Together with literature estimates of the distance and the bolometric flux, these values correspond to linear radii of   and  , and to effective temperatures of  K and  K, respectively.