EDP Sciences
Free access
Volume 367, Number 3, March I 2001
Page(s) 876 - 883
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20000490

A&A 367, 876-883 (2001)
DOI: 10.1051/0004-6361:20000490

The angular diameter and distance of the Cepheid $\zeta$ Geminorum

P. Kervella1, V. Coudé du Foresto2, G. Perrin2, M. Schöller1, W. A. Traub3 and M. G. Lacasse3

1  European Southern Observatory, Karl-Schwarzschildstr. 2, 85748 Garching, Germany
2  Observatoire de Paris-Meudon, 5 place Jules Janssen, 92195 Meudon Cedex, France
3  Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA

(Received 21 September 2000 / Accepted 12 December 2000)

Cepheids are the primary distance indicators for extragalactic astronomy and therefore are of very high astrophysical interest. Unfortunately, they are rare stars, situated very far from Earth. Though they are supergiants, their typical angular diameter is only a few milliarcseconds, making them very challenging targets even for long-baseline interferometers. We report observations that were obtained in the $K^{\prime}$ band (2-2.3 $\mu$m), on the Cepheid $\zeta$ Geminorum with the FLUOR beam combiner, installed at the IOTA interferometer. The mean uniform disk angular diameter was measured to be 1.64 +0.14 -0.16 mas. Pulsational variations are not detected at a significant statistical level, but future observations with longer baselines should allow a much better estimation of their amplitude. The distance to $\zeta$ Gem is evaluated using Baade-Wesselink diameter determinations, giving a distance of 502 $\pm$ 88 pc.

Key words: stars: distances -- stars: individual: $\zeta$ Gem -- stars: oscillations -- stars: Cepheids -- techniques: interferometric

Offprint request: P. Kervella, pkervell@eso.org

SIMBAD Objects in preparation

© ESO 2001

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