Exploring the solar paradigm to explain stellar variability

The emergence of  magnetic field on stellar surfaces leads to the formation of magnetic features, such as dark spots and bright faculae.
These features cause stellar brightness variations. Such variations have been extensively studied for the Sun. The plethora of photometric data obtained by both past (e.g. CoRoT and Kepler) and current space missions (TESS and Gaia) have underlined the needs for a better understanding and modelling of stellar brightness variations. One of the possible approaches for such modelling is to rely on the solar paradigm, i.e. to take a model which reproduces the observed variability of the solar brightness and extend it to other stars.

We follow the SATIRE approach of calculating brightness variations, which was shown to reproduce the solar variability in great detail. To obtain the surface distribution of magnetic features, we employ the FEAT model This allows extending the SATIRE calculations to stars with different rotation periods and inclinations. This allows us to also calculate the rotational variability of stars rotating faster than the Sun. We compare our results to the observed distribution of Kepler stars variability and provide a possible explanation for the observed dependence of the rotational variability on the rotation period for stars rotating slower than 10 days by introducing different degrees of nesting of active regions.