Stellar surface inform. from CaII H&K lines

J/MNRAS/527/2940), we showed on the Sun that different active regions possess unique intensity profiles on the Ca II H & K lines. We now extend the analysis by showing how those properties can be used on real stellar observations, delivering more powerful activity proxies for radial velocity correction.

More information can be extracted on rotational timescale from the Ca II H & K lines than the classical indicators: S-index and log(R'HK). For high-resolution HARPS observations of alpha Cen B, we apply a principal and independent component analysis on the Ca II H & K spectra time-series to disentangle the different sources that contribute to the disk-integrated line profiles. While the first component can be understood as a denoised version of the Mount-Wilson S-index, the second component appears as powerful activity proxies to correct the RVs induced by the inhibition of the convective blueshift in stellar active regions.