Fits of the NLTE Ca II triplet line profiles in β Cet. The dotted line is the observations from NARVAL at TBL with a resolution of  ~ 65 000. The dashed line is the Eriksson et al. (1983) model atmosphere with a chromosphere (T_p = 5500 K). The thin full line is the interpolated MARCS model. The thick full line is our hybrid model with a chromosphere (T_p = 4500). The grey lines below the spectral line profiles show the rotation profiles with a projected rotational velocity of 5 km s^-1.