Magnetic Field and Activity of the Single Late-type Giant Beta Ceti

We present the behavior of the magnetic field and activity indicators of the single late-type giant Beta Ceti in the period June 19, 2010 - December 14, 2010. We used spectropolarimetric data obtained with two telescopes - the NARVAL spectropolarimeter at Telescope Bernard Lyot, Pic du Midi, France and the ESPaDOnS spectropolarimeter at CFHT, Hawaii. The data were processed using the method of Least Square Deconvolution which enables to derive the mean photospheric profiles of Stokes I and V parameters. We measured the surface-averaged longitudinal magnetic field Bl, which varies in the interval 0.1 - 8.2 G, the line activity indicators CaII K, H_alpha, CaII IR (854.2 nm) and radial velocity. By analyzing the Bl variations, was identified a possible rotational period P = 118 days. A single, large magnetic spot which dominates the field topology is a possible explanation for the Bl and activity indicator variations of Beta Ceti.