PCA technique applied to the detection of ZDI circular polarization in solar-type stars

We present a new detection method of ZDI circular polarization applied to observations of solar-type stars. To extract the polarization signal we analyze the observed spectra over intervals of about 2500 A and we take into account the contribution of all spectral lines to the resulting polarization signal. We employ a PCA technique to analyze the synthetic database of profiles. We apply singular value decomposition to the synthetic data over the same spectral range as for the observed data. The principal parameters entering the magnetic spectral synthesis code COSSAM are the effective temperature T-eff and the magnetic field strength B. We find that the first 10 eigenvectors are sufficient to approximate the contribution of all the lines to the resultant averaged circular polarization signal. The principle of this new method can also be employed to detect linear polarization, and it is of course not restricted to solar type stars.