Frequency separation ratios do not suppress magnetic activity effects in solar-like stars

Context. Asteroseismic modelling will play a critical role in future space-based missions such as PLATO, CubeSpec, and Roman . Magnetic activity effects were typically neglected in asteroseismic modelling of solar-type stars, presuming that these effects could be accounted for in the parametrisation of the so-called ‘surface effects’. In recent years, however, it was demonstrated, using both forward and inverse techniques, that magnetic activity can have a significant impact on the asteroseismic characterisation. Aims. We investigated whether frequency separation ratios, which are commonly used to efficiently suppress surface effects, are also able to suppress magnetic activity effects. Methods. Based on GOLF and BiSON observations of the Sun as a star that were segmented into yearly overlapping snapshots, each offset by a quarter of a year, we performed asteroseismic characterisations using frequency separation ratios as constraints to measure the apparent temporal evolution of the stellar parameters and their correlation with the 10.7 cm radio flux, a solar activity proxy. Results. Frequency separation ratios do not suppress the effects of magnetic activity. Both r 01 and r 02 ratios exhibit a clear signature of the magnetic activity cycle. Consequently, when these ratios are employed as constraints in asteroseismic modelling, magnetic activity effects are propagated to the stellar characterisation. Additionally, most stellar parameters correlate with the activity cycle, unlike the direct fitting of individual frequencies. These findings are consistent across both the GOLF and BiSON datasets. Conclusions. Magnetic activity effects significantly impact asteroseismic characterisation within the current modelling framework, regardless of whether forward modelling or inverse methods are used. Moreover, standard techniques to suppress surface effects have proven ineffective against magnetic activity influences. If the latter are used, systematic uncertainties of 4.7%, 2.9%, and 1.0% should be considered for the stellar age, mass, and radius, respectively. In preparation for future space-based photometry missions, it is therefore essential to enhance our theoretical understanding of these effects and develop a modelling procedure capable of accounting for or efficiently suppressing them.