Constraining the near-core rotation of theγDoradus star 43 Cygni using BRITE-Constellation data

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-days 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, high signal-to-noise ratio spectroscopic data obtained at the 1.2m Mercator telescope with the HER-MES 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 ∆Π l=1 of 2970 +700 −570 s. The near-core rotation rate was determined to be f rot = 0.56 +0.12 −0.14 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, υ sin i, of 44 ± 4 km s −1 . Conclusions. The morphology of the observed period spacing patterns shows indications of the presence of a significant chemical gradient in the stellar interior.

Rotation of the convective core in γ Dor stars measured by dips in period spacings of g modes coupled with inertial modes

“…If the rotation period is comparable to the pulsation periods in the co-rotating frame, g-mode period spacings in the inertial frame vary as a function of period (Bouabid et al 2013;Van Reeth et al 2015b;Ouazzani et al 2017;Christophe et al 2018;Li et al 2019a). The property has been used to estimate rotation frequencies in the g mode cavity of 𝛾 Dor stars and SPB (slowly pulsating B) stars (e.g., Van Reeth et al 2016;Ouazzani et al 2017;Zwintz et al 2017;Pápics et al 2017;Christophe et al 2018;Li et al 2019bLi et al , 2020aTakata et al 2020). To calculate g-mode frequencies of a rotating stars, traditional approximation of rotation (e.g., Lee & Saio 1997, TAR), where the horizontal component of angular velocity of rotation, Ω sin 𝜃 is neglected, has been employed in many investigations.…”

Revisiting the pulsational characteristics of the exoplanet host starβPictoris

“…This makes it another candidate for future studies of the physical reasons of amplitude variability versus stability in δ Scuti stars. Our search for g-modes in our data sets was motivated by the idea to use them to probe the near-core region of β Pictoris; the detection of gmodes would allow us to investigate differential rotation in the stellar interiors using prograde and retrograde pulsation modes (e.g., Zwintz et al 2017) and study the angular momentum distribution (e.g., Aerts et al 2017). The absence of a magnetic field (i.e., if there is a magnetic field, its strength has to be lower than 300 G) might also be a crucial factor to be considered when the exoplanetary system and circumstellar disk around β Pictoris are studied.…”

Rotation of the convective core in $γ$ Dor stars measured by dips in period spacings of g modes coupled with inertial modes

“…If the rotation period is comparable to the pulsation periods in the co-rotating frame, g-mode period spacings in the inertial frame vary as a function of period (Bouabid et al 2013;Van Reeth et al 2015b;Ouazzani et al 2017;Christophe et al 2018;Li et al 2019a). The property has been used to estimate rotation frequencies in the g mode cavity of 𝛾 Dor stars and SPB (slowly pulsating B) stars (e.g., Van Reeth et al 2016;Ouazzani et al 2017;Zwintz et al 2017;Pápics et al 2017;Christophe et al 2018;Li et al 2019bLi et al , 2020aTakata et al 2020). To calculate g-mode frequencies of a rotating stars, traditional approximation of rotation (e.g., Lee & Saio 1997, TAR), where the horizontal component of angular velocity of rotation, Ω sin 𝜃 is neglected, has been employed in many investigations.…”