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 that 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 that will bias the results from stellar modelling analysis. Although for most stellar properties this offset should be small, typically less than 0.5 per cent in mass, estimates of age and central hydrogen content can have an error of up to 5 per cent and 3 per cent, 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.
Bibliographical note13 pages, 8 figures
We would like to thank JosefinaMontelb?an for her useful discussions regarding the use of AIMS. AELT,WJC, and GRD acknowledge the support of the Science and Technology Facilities Council (STFC). Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (grant no. DNRF106). AM acknowledges support from the ERC Consolidator Grant funding scheme (project ASTEROCHRONOMETRY; https://www.asterochronometry.eu, G.A. no. 772293).
© 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
- stars: activity
- stars: fundamental parameters
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science