Letters to the Editor

The radius and mass of the close solar twin 18 Scorpii derived from asteroseismology and interferometry^⋆

M. Bazot¹, M. J. Ireland², D. Huber², T. R. Bedding², A.-M. Broomhall³, T. L. Campante^1,4,5, H. Carfantan⁶, W. J. Chaplin³, Y. Elsworth³, J. Meléndez^1,7, P. Petit⁶, S. Théado⁶, V. Van Grootel⁶, T. Arentoft⁴, M. Asplund⁸, M. Castro⁹, J. Christensen-Dalsgaard⁴, J. D. do Nascimento Jr⁹, B. Dintrans⁶, X. Dumusque^1,10, H. Kjeldsen⁴, H. A. McAlister¹¹, T. S. Metcalfe¹², M. J. P. F. G. Monteiro^1,5, N. C. Santos^1,5, S. Sousa¹, J. Sturmann¹¹, L. Sturmann¹¹, T. A. ten Brummelaar¹¹, N. Turner¹¹ and S. Vauclair⁶

¹ Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
e-mail: bazot@astro.up.pt
² Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney NSW 2006, Australia
³ School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
⁴ Institut for Fysik og Astronomi, Aarhus Universitet, Ny Munkegade 1520, 8000 Aarhus C, Danmark
⁵ Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Portugal
⁶ Laboratoire Astrophysique de Toulouse - Tarbes, Université de Toulouse, CNRS, Toulouse, France
⁷ Departamento de Astronomia do IAG/USP, Universidade de São Paulo, Rua do Matão 1226, São Paulo, 05508-900 SP, Brasil
⁸ Max Planck Institute for Astrophysics, Karl-Schwarzschild-Str. 1, Postfach 1317 85741 Garching, Germany
⁹ Universidade Federal do Rio Grande do Norte, Dept de Física Teórica e Experimental, Natal, 59072-970 RN, Brasil
¹⁰ Observatoire de Genève, 51 Chemin des Maillettes, 1290 Sauverny, Suisse
¹¹ Center for High Angular Resolution Astronomy, Georgia State University, PO Box 3965, Atlanta, Georgia 30302-3965, USA
¹² High Altitude Observatory, NCAR, Boulder, CO 80307, USA

Received: 2 September 2010
Accepted: 24 October 2010

Abstract

The growing interest in solar twins is motivated by the possibility of comparing them directly to the Sun. To carry on this kind of analysis, we need to know their physical characteristics with precision. Our first objective is to use asteroseismology and interferometry on the brightest of them: 18 Sco. We observed the star during 12 nights with HARPS for seismology and used the PAVO beam-combiner at CHARA for interferometry. An average large frequency separation 134.4 ± 0.3 μHz and angular and linear radiuses of 0.6759 ± 0.0062 mas and 1.010 ± 0.009 R_⊙ were estimated. We used these values to derive the mass of the star, 1.02 ± 0.03 M_⊙.