  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.
