Tracking Magnetic Variability From High-Resolution Unpolarised Spectra

<p>Discovering Earth-like exoplanets using the radial velocity (RV) technique is mainly being challenged by stellar activity. Only by understanding the variable signals imposed by the star itself will we be able to find the underlying planetary signals. Activity indicators, such as the FWHM of the spectral lines and the Ca II H&K emission, are already being used to understand the stellar variations. However, the high-resolution spectra that we have from the RV searches contain much more information. In this talk I will explain about a new technique of extracting information on the stellar magnetic field directly from the intensity spectrum. By combining thousands of lines, we can extract the Zeeman broadening effect. We apply this to the high-resolution spectra time series taken with HARPS and HARPS-N in order to disentangle the stellar magnetic signal from the signals from Earth-like planets.