Detecting axisymmetric magnetic fields using gravity modes in intermediate-mass stars

J. van Beeck (1) , V. Prat (2) , T. van Reeth (1) , S. Mathis (3, 2) , D. M. Bowman (1) , C. Neiner (3) , C. Aerts (1, 4, 5)

1 Instituut voor Sterrenkunde [Leuven]
2 AIM (UMR_7158 / UMR_E_9005 / UM_112) - Astrophysique Interprétation Modélisation
3 LESIA (UMR_8109) - Laboratoire d'études spatiales et d'instrumentation en astrophysique
4 IMAPP - Institute for Mathematics, Astrophysics and Particle Physics
5 Max Planck Institute for Radio Astronomy

Context. Angular momentum (AM) transport models of stellar interiors require improvements to explain the strong extraction of AM from stellar cores that is observed with asteroseismology. One of the frequently invoked mediators of AM transport are internal magnetic fields, even though their properties, observational signatures, and influence on stellar evolution are largely unknown.Aims. We study how a fossil, axisymmetric internal magnetic field affects period spacing patterns of dipolar gravity mode oscillations in main sequence stars with masses of 1.3, 2.0, and 3.0 M⊙. We assess the influence of fundamental stellar parameters on the magnitude of pulsation mode frequency shifts.Methods. We computed dipolar gravity mode frequency shifts due to a fossil, axisymmetric poloidal–toroidal internal magnetic field for a grid of stellar evolution models, varying stellar fundamental parameters. Rigid rotation was taken into account using the traditional approximation of rotation, and the influence of the magnetic field was computed using a perturbative approach.Results. We find magnetic signatures for dipolar gravity mode oscillations in terminal-age main sequence stars that are measurable for a near-core field strength larger than 105 G. The predicted signatures differ appreciably from those due to rotation.Conclusions. Our formalism demonstrates the potential for the future detection and characterization of strong fossil, axisymmetric internal magnetic fields in gravity-mode pulsators near the end of core-hydrogen burning from Kepler photometry, if such fields exist.

Keywords: asteroseismology; waves; stars: magnetic field; stars: oscillations; stars: rotation

Domains: Physics [physics]; Astrophysics [astro-ph]

J. van Beeck, V. Prat, T. van Reeth, S. Mathis, D. M. Bowman, et al.. Detecting axisymmetric magnetic fields using gravity modes in intermediate-mass stars. Astronomy and Astrophysics - A&A, 2020, 638, pp.A149. ⟨10.1051/0004-6361/201937363⟩. ⟨cea-02882578⟩