Impact of magnetic activity on inferred stellar properties of main sequence Sun-like stars

TL;DR

Magnetic activity in Sun-like stars causes frequency shifts that bias stellar property estimates, especially age and hydrogen content, with the impact depending on activity level and inclination angle.

Contribution

This study quantifies how magnetic activity-induced frequency shifts affect the accuracy of stellar property inference using asteroseismic data.

Findings

Magnetic activity can bias stellar mass estimates by less than 0.5%.

Age and hydrogen content estimates can be biased by up to 5% and 3%.

Biases are larger for more active stars and certain inclination angles.

Abstract

The oscillation frequencies observed in Sun-like stars are susceptible to being shifted by magnetic activity effects. The measured shifts depend on a complex relationship involving the mode type, the field strength and spatial distribution of activity, as well as the inclination angle of the star. Evidence of these shifts is also present in frequency separation ratios which are often used when inferring global properties of stars in order to avoid surface effects. However, one assumption when using frequency ratios for this purpose is that there are no near-surface perturbations that are non-spherically symmetric. In this work, we studied the impact on inferred stellar properties when using frequency ratios that are influenced by non-homogeneous activity distributions. We generate several sets of artificial oscillation frequencies with various amounts of shift and determine stellar properties using two separate pipelines. We find that for asteroseismic observations of Sun-like targets we can expect magnetic activity to affect mode frequencies which will bias the results from stellar modelling analysis. Although for most stellar properties this offset should be small, typically less than 0.5% in mass, estimates of age and central hydrogen content can have an error of up to 5% and 3% respectively. We expect a larger frequency shift and therefore larger bias for more active stars. We also warn that for stars with very high or low inclination angles, the response of modes to activity is more easily observable in the separation ratios and hence will incur a larger bias.