Evolution of magnetic activity on the main sequence as a function of spectral type using Kepler data

Stellar magnetic activity studies are very important for different fields of astrophysics. Several spectroscopic surveys have been aimed at characterizing the magnetic activity of solar-like stars, especially to look for cycles. These surveys were mostly led to put the Sun into context and in time compared to other stars. By investigating the magnetic activity of other stars with different conditions (rotation periods, metallicity…), we can provide additional constraints to dynamo models. Stellar magnetic activity has a direct impact on the habitability of exoplanets hosted by those stars. Consequently, it is important to understand how magnetic activity evolves in time and as a function of spectral type.

The recent catalog of rotation periods and photometric magnetic activity proxies for more than 55,000 stars observed by the Kepler mission opens the possibility to study the surface magnetic activity of a large number of stars. In this talk, we will present a subsample of main-sequence stars in order to compare the Sun to Sun-like stars and show the effect of metallicity using high-resolution spectroscopic data. While we see an interesting behavior as a function of metallicity, we also find that the magnetic activity of the Sun is comparable to the one of stars selected to be very similar to the Sun based on effective temperature, metallicity, and Rossby number, which is the ratio of rotation period and the convective turnover time and is a key parameter in dynamo theory. For all the stars of our sample, we also compute ages based on models taking into account the most recent theory of angular momentum transport that reproduce rotation rates for the Kepler asteroseismic sample. This allows us to study the evolution of magnetic activity as a function of Rossby number and age, providing a more complete picture to understand the changes in the dynamo behaviors during the life of the star until the terminal age main sequence.