Volume 442, Number 2, November I 2005
|Page(s)||567 - 578|
|Section||Stellar structure and evolution|
|Published online||07 October 2005|
Gravitational-darkening of Altair from interferometry
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: email@example.com
2 LESIA, UMR 8109, Observatoire de Paris-Meudon, 5 place Jules Janssen, 92195 Meudon Cedex, France
3 Lab. Univ. d'Astrophysique de Nice (LUAN), UMR 6525, UNSA, Parc Valrose, 06108 Nice Cedex 02, France
4 Astronomical Observatory Belgrade, MNTRS 1940, Volgina 7, 11050 Beograd, Serbia and Montenegro
5 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
6 Department of Physics, University of Redlands, 1200 East Colton Avenue, Redlands, CA 92373, USA
Accepted: 13 June 2005
Interferometric observations have revealed that the rapid rotator Altair is a flattened star with a non-centrally symmetric intensity distribution. In this work we perform for the first time a physically consistent analysis of all interferometric data available so far, corresponding to three different interferometers operating in several spectral bands. These observations include new data (squared visibilities in the H and K bands from VLTI-VINCI) as well as previously published data (squared visibilities in the K band from PTI and squared visibilities, triple amplitudes, and closure phases in the visible between 520 nm and 850 nm from NPOI). To analyze these data we perform a minimization using an interferometry-oriented model for fast rotators, which includes Roche approximation, limb-darkening, and von Zeipel-like gravity-darkening. Thanks to the rich interferometric data set available and to this physical model, the main uniqueness problems were avoided. As a result, we show that the observations can only be explained if Altair has a gravity-darkening compatible with the expected value for hot stars, i.e., the von Zeipel effect ().
Key words: techniques: high angular resolution / techniques: interferometric / methods: data analysis / stars: rotation / stars: individual: Altair
© ESO, 2005
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