Study of HD 169392A observed by CoRoT and HARPS^{⋆,⋆⋆,⋆⋆⋆}

¹ High Altitude Observatory, NCAR, PO Box 3000, Boulder, CO 80307, USA
e-mail: savita.mathur@gmail.com
² Laboratoire AIM, CEA/DSM – CNRS – Univ. Paris Diderot – IRFU/SAp, Centre de Saclay, 91191 Gif-sur-Yvette Cedex, France
³ Danish AsteroSeismology Centre, Department of Physics and Astronomy, University of Aarhus, 8000 Aarhus C, Denmark
⁴ LESIA, UMR 8109, Université Pierre et Marie Curie, Université Denis Diderot, Obs. de Paris, 92195 Meudon Cedex, France
⁵ Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006, Australia
⁶ Laboratoire Lagrange, UMR 7293, Universié de Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, 06304 Nice Cedex 4, France
⁷ CNRS, Institut de Recherche en Astrophysique et Planétologie, 14 avenue Édouard Belin, 31400 Toulouse, France
⁸ Université de Toulouse, UPS-OMP, IRAP, 31400 Toulouse, France
⁹ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
¹⁰ Universidad de La Laguna, Dpto de Astrofísica, 38206 Tenerife, Spain
¹¹ School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
¹² Astronomical Institute Anton Pannekoek, U. of Amsterdam, PO Box 94249, 1090 GE Amsterdam, The Netherlands
¹³ INAF – Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807, Merate (LC), Italy
¹⁴ Astronomy Unit, Queen Mary University of London, Mile End Road, London E1 4NS, UK
¹⁵ Instytut Astronomiczny, Uniwersytet Wroclawski, Kopernika 11, 51-622 Wroclaw, Poland
¹⁶ Institut d’Astrophysique Spatiale, UMR 8617, Université Paris XI, Batiment 121, 91405 Orsay Cedex, France

Received: 24 May 2012
Accepted: 19 September 2012

Abstract

Context. The results obtained by asteroseismology with data from space missions such as CoRoT and Kepler are providing new insights into stellar evolution. After five years of observations, CoRoT is continuing to provide high-quality data and we here present an analysis of the CoRoT observations of the double star HD 169392, complemented by ground-based spectroscopic observations.

Aims. This work aims at characterising the fundamental parameters of the two stars, their chemical composition, the acoustic-mode global parameters including their individual frequencies, and their dynamics.

Methods. We analysed HARPS observations of the two stars to derive their chemical compositions. Several methods were used and compared to determine the global properties of stars’ acoustic modes and their individual frequencies from the photometric data of CoRoT.

Results. The new spectroscopic observations and archival astrometric values suggest that HD 169392 is a weakly bound wide binary system. We obtained spectroscopic parameters for both components which suggest that they originate from the same interstellar cloud. However, only the signature of oscillation modes of HD 169392 A was measured; the signal-to-noise ratio of the modes in HD 169392B is too low to allow any confident detection. For HD 169392 A we were able to extract parameters of modes for ℓ = 0, 1, 2, and 3. The analysis of splittings and inclination angle gives two possible solutions: one with with splittings and inclination angles of 0.4−1.0 μHz and 20 − 40°, the other with 0.2−0.5 μHz and 55−86°. Modelling this star using the Asteroseismic Modeling Portal (AMP) gives a mass of 1.15 ± 0.01 M_⊙, a radius of 1.88 ± 0.02 R_⊙, and an age of 4.33 ± 0.12 Gyr. The uncertainties come from estimated errors on the observables but do not include uncertainties on the surface layer correction or the physics of stellar models.