Stellar Active Latitudes from Seismic Travel Times

The eleven-year solar magnetic activity cycle is known to affect solar acoustic oscillations; higher activity is correlated with an increase in mode frequencies and a decrease in their lifetimes. Activity related frequency shifts have also been observed in other stars, but are difficult to measure mode by mode. Measuring activity induced changes to seismic mode travel times is an alternate method for activity studies and has been shown to be robust to noise. In this work we use a simple forward model to interpret such measurements for the Sun [1] in terms of magnetic activity versus time and latitude. We derive kernels that capture the sensitivity of travel-time measurement to surface activity to different latitudes. We perform linear inversions for the active latitudes using synthetic data and solar data using a regularized least squares technique. We demonstrate the applicability of this method to infer stellar butterfly diagrams. [1] Vasilyev, V., Gizon, L., 2024, A&A, v.682, A142, pp.15