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Astron. Astrophys. 345, 221-232 (1999)


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Interferometric observations of R Leonis in the K band *

First direct detection of the photospheric pulsation and study of the atmospheric intensity distribution

G. Perrin 1, V. Coudé du Foresto 1, S.T. Ridgway 2, B. Mennesson 1, C. Ruilier 1, J.-M. Mariotti 1, W.A. Traub 3 and M.G. Lacasse 3

1 Observatoire de Paris, DESPA, F-92195 Meudon, France
2 National Optical Astronomy Observatories, Tucson, AZ 85726-6732, USA
3 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA

Received 21 December 1998 / Accepted 2 February 1999

Abstract

The Mira-type star R Leonis was observed at two different epochs in the K band with the FLUOR beam combiner on the IOTA interferometer. A variation of diameter is clearly detected for the very first time at this wavelength revealing an apparent pulsation of atmospheric layers very close to the stellar photosphere. We discuss the excess of visibility measured at high spatial frequencies and show that they very likely reveal smaller diameters of the photosphere (22-24 mas) than those deduced on the basis of shorter frequency components. This smaller diameter makes R Leonis a fundamental pulsator. Mira models are compared to our data and a disagreement with spatial intensity distribution and dynamical behaviour is found.

Key words: techniques: interferometric – stars: fundamental parameters – stars: individual: R Leo – stars: AGB and post-AGB – infrared: stars

* based on observations collected at the IOTA interferometer, Whipple Observatory, Mount Hopkins, Arizona.

Send offprint requests to: G. Perrin (perrin@hplyot.obspm.fr)

© European Southern Observatory (ESO) 1999

Online publication: April 12, 1999

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