A&A 399, 275-278 (2003)
DOI: 10.1051/0004-6361:20021796

Infrared high angular resolution measurements of stellar sources

VI. Accurate angular diameters of X Cnc, U Ori and Eta Gem

A. Richichi¹ and G. Calamai<sup>2

1</sup>  European Southern Observatory, Karl-Schwarzschildstr. 2, 85748 Garching bei München, Germany
²  Osservatorio Astrofisico di Arcetri, L.go Enrico Fermi 5, 50125 Firenze, Italy

(Received 25 October 2002 / Accepted 27 November 2002)

Abstract
We present the results of near-IR lunar occultation measurements of three well-known, large angular diameter, cool giant stars, namely X Cnc (CII), U Ori (M8III) and  Gem (M3III). Their 2.2  m angular diameters, derived under the assumption of a uniform circular disk, are , and  milliarcsec, respectively. In the case of U Ori , we find a significant deviation of the brightness profile from circular symmetry, as well as a faint signature of extended emission. The asymmetry of the brightness profile cannot be explained by scintillation effects in the lunar occultation lightcurve, and could have contributed to the important differences in previous determinations of the angular diameter of U Ori in the near-IR. Also in the case of  Gem , significant differences exist among the available angular diameter determinations.

Key words: techniques: high angular resolution -- stars: fundamental parameters -- stars: individual: X Cnc -- stars: individual: U Ori -- stars: individual: Eta Gem

Offprint request: A. Richichi, arichich@eso.org

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