Constraining the near-core rotation of the γ Doradus star 43 Cygni using BRITE-Constellation data^⋆,⋆⋆

¹ Institut für Astro- und Teilchenphysik, Universität Innsbruck, Technikerstrasse 25/8, 6020 Innsbruck, Austria
e-mail: konstanze.zwintz@uibk.ac.at
² Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
³ Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106, USA
⁴ Instytut Astronomiczny, Uniwersytet Wroclawski, ul. Kopernika 11, 51-622 Wroclaw, Poland
⁵ Institut für Kommunikationsnetze und Satellitenkommunikation, Technical University Graz, Inffeldgasse 12, 8010 Graz, Austria
⁶ Nicolaus Copernicus Astronomical Center, ul. Bartycka 18, 00-716 Warsaw, Poland
⁷ Département de physique and Centre de Recherche en Astrophysique du Québec (CRAQ), Université de Montréal, CP 6128, Succ. Centre-Ville, Montréal, Québec H3C 3J7, Canada
⁸ Institute of Automatic Control, Silesian University of Technology, Akademicka 16, 44-100 Gliwice, Poland
⁹ Department of Physics, Royal Military College of Canada, PO Box 17000, Station Forces, Kingston, Ontario K7K 7B4, Canada
¹⁰ Institut für Astrophysik, Universität Wien, Türkenschanzstrasse 25/8, 1180 Vienna, Austria

Received: 16 August 2017
Accepted: 6 October 2017

Abstract

Context. Photometric time series of the γ Doradus star 43 Cyg obtained with the BRITE-Constellation nano-satellites allow us to study its pulsational properties in detail and to constrain its interior structure.

Aims. We aim to find a g-mode period-spacing pattern that allows us to determine the near-core rotation rate of 43 Cyg and redetermine the star’s fundamental atmospheric parameters and chemical composition.

Methods. We conducted a frequency analysis using the 156-day long data set obtained with the BRITE-Toronto satellite and employed a suite of MESA/GYRE models to derive the mode identification, asymptotic period-spacing, and near-core rotation rate. We also used high-resolution spectroscopic data with high signal-to-noise ratio obtained at the 1.2 m Mercator telescope with the HERMES spectrograph to redetermine the fundamental atmospheric parameters and chemical composition of 43 Cyg using the software Spectroscopy Made Easy (SME).

Results. We detected 43 intrinsic pulsation frequencies and identified 18 of them to be part of a period-spacing pattern consisting of prograde dipole modes with an asymptotic period-spacing ΔΠ_{l = 1} of 2970_-570⁺⁷⁰⁰ s. The near-core rotation rate was determined to be f_rot = 0.56_-0.14^+0.12 d^-1. The atmosphere of 43 Cyg shows solar chemical composition at an effective temperature, T_eff, of 7150 ± 150 K, a log g of 4.2 ± 0.6 dex, and a projected rotational velocity, υsini, of 44 ± 4 km s^-1.

Conclusions. The morphology of the observed period-spacing patterns shows indications of a significant chemical gradient in the stellar interior.