Seismic signature of a magnetic field in the γ Doradus star KIC 2309579

Internal magnetic fields have recently been detected and measured in the radiative core of red giant stars using asteroseismology. As they are one of the progenitors of red giant stars and exhibit high radial order gravity modes, γ Doradus stars may also hold detectable magnetic fields in their radiative envelope. We aim to detect, for the first time, an internal magnetic field in a rapidly rotating γ Doradus star through its influence on the propagation of Kelvin gravito-inertial modes. We used the seismic variable dKa, defined as a combination of Kelvin modes frequencies, which is sensitive to the presence of a magnetic field. Following the detection, we modeled the star oscillation spectrum while considering a magnetic component following a Bayesian approach. We found a magnetic signature in the radiative envelope of If located just above the core, in the layers that were previously convective, the magnetic field would reach ∼ 4 kG.