The HARPS/HARPS-N Data Reduction Software ( DRS ) relies on the cross-correlation between the observed spectra and a suitable stellar mask to compute a cross-correlation function ( CCF ) to be used both for the radial velocity ( RV ) computation and as an indicator of stellar lines asymmetry , induced for example by the stellar activity .
Unfortunately the M2 mask currently used by the HARPS/HARPS-N DRS for M-type stars results in heavily distorted CCFs .

We created several new stellar masks in order to decrease the errors in the RVs and to improve the reliability of the activity indicators as the bisector ’ s span .

We obtained very good results with a stellar mask created from the theoretical line list provided by the VALD3 database for an early M-type star ( T _ { \mathrm { eff } } =3500 K and \log { g } = 4.5 ) .
The CCF ’ s shape and relative activity indicators improved and the RV time-series allowed us to recover known exoplanets with periods and amplitudes compatible with the results obtained with HARPS-TERRA .