Influence of magnetic activity on the determination of stellar parameters through asteroseismology

Abstract

Magnetic activity changes the gravito-acoustic modes of solar-like stars and in particular their frequencies. There is an angular-degree dependence that is believed to be caused by the non-spherical nature of the magnetic activity in the stellar convective envelope. These changes in the mode frequencies could modify the small separation of low-degree modes (i.e. frequency difference between consecutive quadrupole and radial modes), which is sensitive to the core structure and hence to the evolutionary stage of the star. Determining global stellar parameters such as the age using mode frequencies at a given moment of the magnetic activity cycle could lead to biased results. Our estimations show that in general these errors are lower than other systematic uncertainties, but in some circumstances they can be as high as 10% in age and of a few percent in mass and radius. In addition, the frequency shifts caused by the magnetic activity are also frequency dependent. In the solar case this is a smooth function that will mostly be masked by the filtering of the so-called surface effects. However the observations of other stars suggest that there is an oscillatory component with a period close to the one corresponding to the acoustic depth of the He II zone. This could give rise to a misdetermination of some global stellar parameters, such as the helium abundance. Our computations show that the uncertainties introduced by this effect are lower than the 3% level.

Paper accepted for publication in Frontiers Astronomy and Space Sciences. 24 pages and 9 figures

References in corpus (12)

• Modules for Experiments in Stellar Astrophysics (MESA)
• The K2 Mission: Characterization and Early results
• ADIPLS -- the Aarhus adiabatic oscillation package
• Correcting stellar oscillation frequencies for near-surface effects
• CoRoT reveals a magnetic activity cycle in a Sun-like star
• The effect of magnetic topology on thermally-driven winds: towards a general formulation of the braking law
• The First APOKASC Catalog of Kepler Dwarf and Subgiant Stars
• The influence of metallicity on stellar differential rotation and magnetic activity
• Stellar magnetic activity and variability of oscillation parameters - An investigation of 24 solar-like stars observed by Kepler
• The asteroseismic surface effect from a grid of 3D convection simulations. I. Frequency shifts from convective expansion of stellar atmospheres
• The Sun's interior structure and dynamics, and the solar cycle
• Parametrizing the time-variation of the "surface term" of stellar p-mode frequencies: application to helioseismic data

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• Empirical Relations for the Sensitivities of Solar-like Oscillations to Magnetic Perturbations
• Asteroseismic modelling of main-sequence solar-like stars and Kepler exoplanet host stars with the FICO procedure I. Catalogue of fundamental stellar properties
• Dynamical mass of a solar-like oscillator at the main-sequence turnoff from Gaia astrometry & ground-based spectroscopy
• K2-99 revisited: a non-inflated warm Jupiter, and a temperate giant planet on a 522-d orbit around a subgiant